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PC 2017-09-05_9a Bridge Street Bridge Project_IS-MNDMEMORANDUM TO : PLANNING COMMISSION FROM: TERESA MCCLISH, COMMUNITY DEVELOPMENT DIRECTOR SUBJECT: CONSIDERATION OF DRAFT INITIAL STUDY/MITIGATED NEGATIVE DECLARATION FOR THE BRIDGE STREET BRIDGE REHABILITATION PROJECT DATE; SEPTEMBER 5, 2017 RECOMMEN DATlON: It is recommended that the Planning Commission: 1. Review the Draft Initial Study/Mitigated Negative Declaration (IS/M ND) for the proposed Bridge St Bridge Rehabi litation project; and 2. Make a recom mendation to the City Council to adopt the MND , and instruct the City Clerk to file a Notice of Determination (NOD). SUMMARY OF ACTION: A doptin g and certifying th e MND for t he proj ect will prov ide necessary environ menta l clearance in order to proceed with final design for the proj ect. IMPACT ON FINANCI AL AND PERSONNEL RESOURCES: The City has been successful in securing 100% funding through the Local Hig hway Bridge Program (HBP) funds for the Bridge Street Bridge project, including consultant costs for required technical studi es and environmental documentation. This item is id entified in the recently adopted City Counci l Goals with regard to supporting City infrastructure. BACKGROUND: On January 27 , 2015, Council selected two alternatives with which to proceed for environm ental study for the Bridge Street Bridge Improvement Project ("P roj ect"): 1) the .C?ep/acement Alternative that w ould sa lvage and relocate the truss on a new b ridge; and 2) the Reh abilitaUc/1 Alfemalive tha t wou ld rep lace the existing supplemental truss with a new supple me nt al truss constructed to hand le 100% of modem design loads. PLANNING COMMISSION CONSIDERATION OF DRAFT INITIAL STUDY/MITIGATED NEGATIVE DECLARATION FOR THE BRIDGE STREET BRIDGE REHABILITATION PROJECT SEPTEMBER 5, 2017 PAGE2 On January 27, 2015, the Council also approved an amendment with Quincy Engineering, Inc. to allow the consultant team to carry the two altematives through the environmental process. In response, the consultant team proceeded with preparation of the technical studies for the two alternatives•and has brought both alternatives to a 65% design level. On January 24, 2017, the Council received a project status update for the Bridge Street Bridge project. and based on one of the required analyses called "the Finding of No Adverse Effecf', concurrence with the Caltrans review team, and a recommendation from the Bridge St. Bridge Stakeholders Group, eliminated the replacement alternative from further consideration for the project. ANALYSIS OF ISSUES: As the rehabilitation alternative does not result in an adverse effect to a significant resource, the City prepared an initiai StudyiMitigate<i Negative Declaration (IS/MND} consistent with the California Environmental Quality Act (Attachment 1 ). On July 24, 2017, the Draft IS/MND was publically noticed for circulation and sent to the State Clearinghouse and Planning Unit. No public comments were received. The project report and environmental documents were prepared in coordination with California Department of Transportation (Caltrans). The MND evaluates potential impacts associated with the rehabilitation and structural improvements of the Bridge Street Bridge (Bridge No. 49C0196) over Arroyo Grande Creek. The purpose of the proposed project is to improve public safety, reduce future maintenance costs, and preserve, to the greatest extent possible, the historic character of the Bridge Street Bridge. The project would provide a rehabilitated bridge that would increase the load carrying capacity, improve safeiy, upgrade bridge railings to curreni Association of State Highway and Transportation Officials (AASHTO) standards and balance the structural design with the community's desire for historic presel\lation. If the bridge is not rehabilitated, current conditions would continue to deteriorate and eventually bridge closure would be required. The MND identified nine (9) areas of potential impact that required mitigation measures: biological resources, transportation/traffic, cultural resources, hazards and hazardous resources, tribal cultural resources, air quality, hydrology and water quality, noise and recreation. The MND includes analyses of each potential impact with mitigation measures and includes the required monitoring plan. Additionally, the project report prepared by Quincy Engineering is included for further information on the project (Attachment 2). There have been several technical studies and agency concurrences prepared in support of the MND and concurrent National Environmental Policy Act (NEPA) process for which Caltrans is the lead agency. Once the environmental clearance is complete, the City may proceed with final plans, specifications an d estimates. PLANNING COMMISSION CONSIDERATION OF DRAFT INITIAL STUDY/MITIGATED NEGATIVE DECLARATION FOR THE BRIDGE STREET BRIDGE REHABILITATION PROJECT SEPTEMBER 5, 2017 PAGE3 ALTERNATIVES: The following alternatives are provided for the Commission's consideration: 1. Recommend that the City Council approve staffs recommendations; 2. Do not recommend that the City Council approve staffs recommendations and request further information; 3. Modify staff's recommendation and recommend approval to City Council; or 4. Provide direction to staff. ADVANTAGES: Recommending approval of the MND to Council will provide an opportunity to review for adequacy, the analysis of potential environmental impacts of the Project and proposed mitigation measures prior to approving the project. DISADVANTAGES: None identified. ENVIRONMENTAL REVIEW: The Initial Study/Mitigated Negative Declaration (IS/MND) has been prepared by SWCA Consultants under contract with Quincy Engineering and reviewed by City Staff. The purpose is to evaluate the potential environmental effects of the proposed Project. This document has been prepared in accordance with the California Environmental Quality Act (CEQA), Public Resources Code §21000 et seq., and the State CEQA Guidelines, California Code of Regulations (CCR) §15000 et seq. PUBLIC NOTIFICATION AND COMMENTS: The Agenda was posted at City Hall and on the City's website in accordance with Government Code Section 54954.2. Attachment: 1. Initial Study/Mitigated Negative Declaration 2. Project Report (without appendices) INITIAL STUDY/ PROPOSED MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project City of Arroyo Grande, County of San Luis Obispo, California Existing Bridge No. 49C0196 Federal Aid Project ID BRLO-5199 (027) July 2017 INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 2 of 100 Project: Bridge Street Bridge Rehabilitation Project Lead Agency: City of Arroyo Grande Document Availability: • City of Arroyo Grande Community Development Department 300 East Branch Street Arroyo Grande, CA 93420 • Arroyo Grande Library 800 West Branch Street Arroyo Grande, CA 93420 • http://www.arroyogrande.org/ Project Description: In coordination with California Department of Transportation (Caltrans), the City of Arroyo Grande proposes to rehabilitate and address structural deficiencies associated with the Bridge Street Bridge (Bridge No. 49C0196) over Arroyo Grande Creek. The purpose of the proposed project is to improve public safety, reduce future maintenance costs, and preserve, to the greatest extent possible, the historic character of the Bridge Street Bridge. The project would provide a rehabilitated bridge that would increase the load carrying capacity, improve safety, upgrade bridge railings to current Association of State Highway and Transportation Officials (AASHTO) standards and balance the structural design with the community’s desire for historic preservation. If the bridge is not rehabilitated, current conditions would continue to deteriorate and eventually bridge closure would be required. Summary Document Preparation: Pursuant to Section 21082.1 of the California Environmental Quality Act, the City of Arroyo Grande (the City) has independently reviewed and analyzed the Initial Study and Proposed Mitigated Negative Declaration (IS/MND) for the proposed project and finds that these documents reflect the independent judgment of the City. The City, as lead agency, also confirms that the project mitigation measures detailed in these documents are feasible and will be implemented as stated in the IS/MND. ______________________________________ 7/18/2017 Prepared by: Emily Creel, JD Date SWCA Environmental Consultants, Planning Team Lead ______________________________________ Reviewed by: Teresa McClish, AICP Date Community Development Director INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 3 of 100 Table of Contents: 1. Introduction .......................................................................................................................................... 5 Introduction and Regulatory Guidance..................................................................................................... 5 Lead Agency .............................................................................................................................................. 5 Purpose and Document Organization ....................................................................................................... 5 Summary of Findings................................................................................................................................. 6 2. Project Description ................................................................................................................................ 7 Project Location ........................................................................................................................................ 7 Existing Bridge ........................................................................................................................................... 7 Project Objectives ................................................................................................................................... 10 Proposed Bridge Rehabilitation .............................................................................................................. 10 Other Required Public Agency Approvals ............................................................................................... 15 Related Projects ...................................................................................................................................... 15 3. Environmental Checklist ..................................................................................................................... 16 Project Information ................................................................................................................................. 16 Environmental Factors Potentially Affected ........................................................................................... 17 Determination ......................................................................................................................................... 17 Evaluation of Environmental Impacts ..................................................................................................... 18 4. Environmental Issues .......................................................................................................................... 19 I. Aesthetics ............................................................................................................................................. 19 II. Agriculture and Forestry Resources .................................................................................................... 20 III. Air Quality .......................................................................................................................................... 22 IV. Biological Resources .......................................................................................................................... 27 V. Cultural Resources .............................................................................................................................. 39 VI. Geology and Soils ............................................................................................................................... 42 VII. Greenhouse Gas Emissions ............................................................................................................... 45 VIII. Hazards and Hazardous Materials ................................................................................................... 47 IX. Hydrology and Water Quality ............................................................................................................ 51 X. Land Use and Planning ........................................................................................................................ 56 XI. Mineral Resources ............................................................................................................................. 59 XII. Noise ................................................................................................................................................. 59 XIII. Population and Housing ................................................................................................................... 62 XIV. Public Services ................................................................................................................................. 63 XV. Recreation ......................................................................................................................................... 65 XVI. Transportation/Traffic ..................................................................................................................... 66 INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 4 of 100 XVII. Tribal Cultural Resources ................................................................................................................ 69 XVIII. Utilities and Service Systems ......................................................................................................... 70 5. Mandatory Findings of Significance .................................................................................................... 72 6. Mitigation Monitoring and Reporting Program .................................................................................. 74 7. References .......................................................................................................................................... 98 INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 5 of 100 1. Introduction Introduction and Regulatory Guidance This Initial Study/Mitigated Negative Declaration (IS/MND) has been prepared by the City of Arroyo Grande (the City) to evaluate the potential environmental effects of the proposed Bridge Street Bridge Rehabilitation Project (project). This document has been prepared in accordance with the California Environmental Quality Act (CEQA), Public Resources Code §21000 et seq., and the State CEQA Guidelines, California Code of Regulations (CCR) §15000 et seq. An Initial Study is conducted by a lead agency to determine if a project may have a significant effect on the environment (State CEQA Guidelines §15063). If there is substantial evidence that a project may have a significant effect on the environment, an Environmental Impact Report (EIR) must be prepared, in accordance with State CEQA Guidelines §15064(a). However, if the lead agency determines that revisions in the project plans or proposals made by or agreed to by the applicant mitigate the potentially significant effects to a less-than-significant level, an MND may be prepared instead of an EIR (State CEQA Guidelines §15070). The lead agency prepares a written statement describing the reasons a proposed project would not have a significant effect on the environment and, therefore, why an EIR need not be prepared. This IS/MND conforms to the content requirements under State CEQA Guidelines §15071. Lead Agency The lead agency is the public agency with primary approval authority over the proposed project. In accordance with State CEQA Guidelines §15051(b)(1), "the lead agency will normally be an agency with general governmental powers, such as a city or county, rather than an agency with a single or limited purpose.” The lead agency for the proposed project is the City of Arroyo Grande. The contact person for the lead agency is: Teresa McClish, AICP Community Development Director City of Arroyo Grande 300 E. Branch Street Arroyo Grande, CA 93420 T: (805) 473-5420 E: tmcclish@arroyogrande.org Purpose and Document Organization The purpose of this document is to evaluate the potential environmental effects of the proposed project. Mitigation measures have been identified and incorporated into the project to eliminate or reduce any potentially significant impacts to a less-than-significant level. This document is organized as follows: 1. Introduction – This chapter provides an introduction to the project and describes the purpose and organization of this document. 2. Project Description – This chapter describes the background and scope of the project, all proposed project components, and identifies project objectives. INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 6 of 100 3. Environmental Checklist – This chapter summarizes the project and the environmental issues to be considered, and describes the process for evaluation of environmental impacts. 4. Environmental Setting, Potential Impacts, and Mitigation Measures – This chapter explains the environmental setting for each environmental issue area, identifies the significance of potential environmental impacts, and evaluates the potential impacts identified in the CEQA Environmental (Initial Study) Checklist. Mitigation measures are incorporated, where appropriate, to reduce potentially significant impacts to a less-than-significant level. 5. Mandatory Findings of Significance – This chapter identifies and summarizes the overall significance of any potential impacts to natural and cultural resources, cumulative impacts, and impact to humans, as identified in the Initial Study. 6. Summary of Mitigation Measures – This chapter summarizes the mitigation measures incorporated into the project as a result of the Initial Study. 7. References – This chapter identifies the references and sources used in the preparation of this IS/MND. Summary of Findings Chapter 3 of this document contains the Environmental (Initial Study) Checklist that identifies the potential environmental impacts (by environmental issue) and contains a brief discussion of each potential impact that would result from implementation of the proposed project. In accordance with §15064(f) of the State CEQA Guidelines, an MND shall be prepared if the proposed project will not have a significant effect on the environment after the inclusion of mitigation measures in the project. Based on the available project information and the environmental analysis presented in this document, there is no substantial evidence that, after the incorporation of identified mitigation measures, the proposed project would have a significant effect on the environment. It is proposed that an MND be adopted in accordance with the State CEQA Guidelines. INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 7 of 100 2. Project Description Project Location The Bridge Street Bridge (49C0196), over Arroyo Grande Creek, is located within the city of Arroyo Grande, San Luis Obispo County, California. The bridge is located approximately 0.2 mile east of U.S. Route 101 (US 101). Bridge Street Bridge is an off-system local urban road that follows a north-south corridor through the downtown area of the city. Surrounding land uses consist of an urbanized business district. The project vicinity and location are illustrated in Figures 1 and 2. Existing Bridge The existing bridge is a hybrid structure comprised of an original Pratt pony through truss, which is now supported by a supplemental steel deck truss. The structure also has a single southern approach span consisting of a reinforced concrete deck supported by steel stringers. The main truss span is approximately 100 feet long and the approach span is approximately 24 feet long. Two seat-type abutments and a single pier supports the northern end of the approach span and southern end of the main truss. The pier consists of one approximately 4-foot-diameter reinforced concrete pile extension under each truss bearing, which are joined together by a reinforced concrete closure wall. The original 24-foot-wide pony truss was built in 1908 and carries two traffic lanes with pedestrian sidewalks cantilevered on both sides outside of the truss members. In 1914, a large flow event in Arroyo Grande Creek washed out the southern approach embankment, which resulted in the addition of the single-approach span. The existing southern abutment was replaced in the channel and now serves as an intermediate pier. A new steel stringer approach span and concrete abutment were constructed on the newly formed southern embankment. The sidewalks are composed of timber supported on steel brackets attached to the truss and approach span stringers. This original bridge structure was first inspected by the California Department of Transportation (Caltrans) in 1939 and was load posted at that time for 10 tons per vehicle and 17 tons per semi-truck combination. Bridge inspection records indicate that portions of the approach span deck failed in 1970 causing a temporary closure of the bridge while the reinforced concrete deck in the first span was replaced. The load posting for the structure was then reduced to 5 tons for all vehicles. A further inspection in 1985 revealed a failed truss diagonal member, which resulted in load posting of 3 tons. In 1989, a vehicle collided with a vertical latticed truss post and severely damaged it. Upon investigation of the bridge condition after this crash, severe corrosion of the bridge’s crossbeams was discovered and the bridge was closed to all traffic. The City Council elected to repair the bridge through design and installation of a supplemental steel deck truss (carrier truss) installed underneath the original pony truss, which allowed for legal loads of 20 Ton-23 Ton-25 Ton Truck configurations. During final design of this structural strengthening system, it was discovered that the concrete comprising the bridge abutments was of poor quality and relatively low strength. At that time, the City elected to defer further repairs to the bridge until a later date. INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 8 of 100 Figure 1. Project Vicinity Map INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 9 of 100 Figure 2. Project Location Map INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 10 of 100 In 1997, Caltrans completed a supplemental inspection and determined that a portion of the concrete supporting the exterior stringer for the approach span had been removed in order to install the supporting carrier truss. This pier modification resulted in an unsupported cantilever section, which reduced the bearing capacity under the exterior stringer. This condition is the primary reason the bridge has remained posted for 3 tons per vehicle. As a result of the observed level of deterioration, the existing bridge is considered structurally deficient. No previous studies have evaluated the existing bridge for seismic or scour deficiencies. As-built plans of the substructure cannot be found, so this analysis is not possible. Project Objectives The City proposes to rehabilitate and address structural deficiencies associated with the Bridge Street Bridge (Bridge No. 49C0196) over Arroyo Grande Creek. The existing bridge is structurally deficient and has been limited to 3-ton loads since 1985, which is the lowest posting allowed before bridge closure is required. The existing bridge is structurally deficient to carry vehicular live loads and has significant seismic deficiencies as well as possible foundation settlement and tilting. The Bridge Street Bridge has been identified as one of the best California examples of a “classic” pony truss and was determined eligible for listing in the National Register of Historic Places (NRHP) in the 1980s. The purpose of the proposed project is to improve public safety, reduce future maintenance costs, and preserve, to the greatest extent possible, the historic character of the Bridge Street Bridge. The project would rehabilitate the existing bridge to increase load-carrying capacity, improve safety, upgrade bridge railings to current Association of State Highway and Transportation Officials (AASHTO) standards, and balance the structural design with the community’s dedication to historic preservation. If the bridge is not rehabilitated, the existing structure would continue to deteriorate and eventually bridge closure would be required. Proposed Bridge Rehabilitation The proposed bridge rehabilitation consists of replacing the existing supplemental truss with a new higher-strength supplemental truss in order to increase live-load capacity. A new substructure consisting of cast-in-place abutments and a pier along with a new steel girder approach span and cast-in-place deck would be constructed to upgrade the structure to the latest scour and seismic codes. Refer to Figures 3a and 3b for project plans. To rehabilitate the structure, all portions of the existing bridge would be removed (the existing historic truss would be salvaged for later reinstallation on the new stronger supplemental truss). After the existing bridge substructure is removed, a new substructure would be constructed. Since the existing 100-foot-long truss length is set, a new pier in the channel would be required near the existing pier location. The existing 25-foot-long steel girder approach span would also be replaced with a new approximately 39-foot-long steel girder approach span with a new cast-in-place concrete deck. After the new substructure is complete, a new supplemental structure would be designed to handle 100% of the current design live loads as well as support the weight of the historic truss. The supplemental structure design would consist of a three-truss system with lateral cross bracings to provide additional support. It was not feasible to increase the depth of the new supplemental truss due to the existing water surface elevation; therefore, additional chord panels are proposed to provide increased structural capacity. The supplemental truss would be painted brown similar to the existing supplemental truss. INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 11 of 100 The historic truss would be removed and disassembled during new foundation construction. The existing lead-based paint would be removed and a new coating that matches the existing color would be applied. Most historic truss members would remain unaltered from the existing condition with the exception of the existing concrete deck and floor beams (floor beams are steel girders that are cast in the concrete deck and connect the two truss elements together). New floor beams will not be encased in concrete so that they can be regularly inspected and maintained. They will be approximately 3 feet longer than the existing beams and a new concrete deck with a curb will be used to connect the truss elements together. The total bridge width would be approximately 40 feet 6 inches. The existing cantilevered sidewalk members (and railings) would be replaced on the rehabilitated structure unaltered. Rivets and pins that are removed as necessary to disassemble the truss would be replaced with rivet bolts and pins that look similar to the existing ones. Geotechnical/Foundations Cast-in-Drilled Hole (CIDH) piles would be utilized to support the rehabilitation project. These foundations would involve drilling holes, and possibly using drilling slurry, temporary casings, and/or permanent casings to reduce the potential for caving of native materials. After the holes are drilled, a reinforcing cage would be lowered in place, and concrete would be pumped into the hole. Currently, 30-inch-diameter piles are proposed at the abutments and a single 60- to 84-inch-diameter pile extension is proposed at the center pier. Drainage The existing bridge allows roadway drainage to sheet flow directly into Arroyo Grande Creek. Current environmental permit requirements usually specify that the stormwater on bridges be collected and transported off the bridge into a roadway drainage facility. The proposed project would be crowned at the roadway centerline and utilize concrete curbs and a longitudinal slope in order to convey and collect the stormwater. Eventually, the roadway drainage system would be conveyed into the creek through exiting culverts as part of the existing stormwater collection system. The existing culvert outlets may need to be modified in order to allow compliance with PR1 (Site Design and Runoff Reduction) and PR2 (Water Quality Treatment) post-construction stormwater standards. Utilities The utilities present on the bridge are owned by the City and include a 6-inch diameter ductile iron water supply line and an 8-inch diameter ductile iron sanitary sewer line that were upgraded in 1997. Temporary utility relocations would be required during construction. Construction Staging and Equipment Construction staging areas would be established within Kiwanis Park along Olohan Alley and in the surface parking lot associated with the historic Arroyo Grande Independent Order of Odd Fellows (IOOF) Hall located at 128 Bridge Street. The existing access and parking lot for the IOOF Hall would be maintained throughout construction. Equipment anticipated to be used in the proposed project includes excavators, dozers, cranes, dump trucks, concrete trucks, concrete pumps, and pile drilling equipment. Removal of the existing bridge would require excavators, hoe rams, cranes, and dump trucks. INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 12 of 100 Traffic Control/Detour Because the bridge would be rehabilitated on the existing alignment, road closures during construction would be required. There are available detours along Traffic Way or Mason Street adjacent to the Bridge Street Bridge. The closures would be coordinated around the Strawberry and Harvest Festivals to the extent possible in order to minimize impacts to the public. Road closures would eliminate staged construction, which would reduce construction time and construction costs. Right-of-Way The project is located in a developed urban area within a 60-foot-wide City right-of-way centered along the existing road. No additional right-of-way acquisitions would be required to construct this project; however, temporary construction easements would be required to provide room for construction and contractor staging areas. Construction Schedule Construction is expected to last approximately 8 months. When construction activities are complete, the project site would be restored and revegetated. Construction Access The proposed project would involve minor modifications/alterations to the creek, including the placement of a temporary road in the creek in order to allow for contractor access. This access road is necessary to facilitate bridge removal and place the temporary bridge supports (falsework) for installation of the new pile foundations. Construction would require clearing of the vegetation below and adjacent to the bridge. Cofferdams, stream diversion, and dewatering may also be required to provide a work area. Following construction, the temporary fill for the access road and diversion would be removed and the creek would be restored to the existing topographic contours. INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 13 of 100 Figure 3a. Site Plan INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 14 of 100 Figure 3b. Site Plan INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 15 of 100 Other Required Public Agency Approvals Project construction and implementation would require the City to obtain permits and other forms of approval from various federal and state agencies. These authorizations may be issued in the form of regulatory permits, agreements, or other forms of environmental review or approval. Authorizations will likely include numerous requirements for environmental compliance, which will be enforced through construction monitoring, documentation, and reporting. As proposed, the project is expected to require authorizations/permits from the following agencies: Table 1. Agency Permits/Authorizations Responsible Agency Applicable Permit or Authorization City of Arroyo Grande CEQA Lead Agency Environmental Clearance/Adoption California Department of Transportation (Caltrans) National Environmental Policy Act (NEPA) Lead Agency Clearance/Approval U.S. Fish and Wildlife Service (USFWS) Section 7 Biological Opinion National Oceanic and Atmospheric Association (NOAA) Section 7 Biological Opinion State Water Resources Control Board (SWRCB)/ Regional Water Quality Control Board (RWQCB) Clean Water Act §401 Water Quality Certification United States Army Corps of Engineers (USACE) Clean Water Act §404 Permit California Department of Fish and Wildlife (CDFW) Section 1602 Streambed Alteration Agreement San Luis Obispo County Air Pollution Control District (APCD) Construction Permits, if necessary Related Projects The proposed project is not related to any other past, present, or future planned projects. INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 16 of 100 3. Environmental Checklist Project Information Project Title: Bridge Street Bridge Rehabilitation Project Lead Agency Name & Address: City of Arroyo Grande 300 East Branch Street Arroyo Grande, CA 93420 Contact Person & Telephone Number: Teresa McClish, Community Development Director (805) 473-5420 Project Location: Bridge Street Bridge (Bridge No. 49C0196) over Arroyo Grande Creek, Arroyo Grande, California Project Sponsor Names & Addresses: City of Arroyo Grande 300 East Branch Street Arroyo Grande, CA 93420 General Plan Designation: Village Core with Historic Character and Conservation/Open Space Overlays Zoning: Village Mixed Use, Village Core Downtown, Design Overlay D-2.4, and Public Facility Description of Project: Rehabilitation of the Bridge Street Bridge along the existing alignment Surrounding Land Uses & Setting: Downtown commercial, retail, and community facilities; Arroyo Grande Creek and riparian corridor; Kiwanis Park Approval Required from Other Public Agencies: Caltrans, SWRCB/RWQCB, USFWS, NOAA, USACE, CDFW, APCD INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 17 of 100 Environmental Factors Potentially Affected The environmental factors checked below would be potentially affected by this project, involving at least one impact that is a "Potentially Significant Impact,” as indicated by the checklist on the following pages: Aesthetics Agricultural Resources Air Quality Biological Resources Cultural Resources Geology/Soils Greenhouse Gas Emissions Hazards & Hazardous Materials Hydrology/Water Quality Land Use/Planning Mineral Resources Noise Population/Housing Public Services Recreation Transportation/Traffic Tribal Cultural Resources Utilities/Service Systems Mandatory Findings of Significance Determination On the basis of this initial evaluation: I find that the proposed project COULD NOT have a significant effect on the environment and a NEGATIVE DECLARATION will be prepared. I find that, although the original scope of the proposed project COULD have a significant effect on the environment, there WILL NOT be a significant effect because revisions/mitigations to the project have been made by or agreed to by the applicant. A MITIGATED NEGATIVE DECLARATION will be prepared. I find that the proposed project MAY have a significant effect on the environment and an ENVIRONMENTAL IMPACT REPORT or its functional equivalent will be prepared. I find that the proposed project MAY have a "potentially significant impact" or "potentially significant unless mitigated impact" on the environment. However, at least one impact has been adequately analyzed in an earlier document, pursuant to applicable legal standards, and has been addressed by mitigation measures based on the earlier analysis, as described in the report's attachments. An ENVIRONMENTAL IMPACT REPORT is required, but it must analyze only the impacts not sufficiently addressed in previous documents. I find that, although the proposed project could have had a significant effect on the environment, because all potentially significant effects have been adequately analyzed in an earlier EIR or Negative Declaration, pursuant to applicable standards, and have been avoided or mitigated, pursuant to an earlier EIR, including revisions or mitigation measures that are imposed upon the proposed project, all impacts have been avoided or mitigated to a less-than- significant level and no further action is required. ______________________________________ Teresa McClish, AICP Date Community Development Director INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 18 of 100 Evaluation of Environmental Impacts 1. A brief explanation, adequately supported by the information sources cited, is required for all answers, except "No Impact.” A "No Impact" answer is adequately supported if the referenced information sources show that the impact does not apply to the project being evaluated (e.g., the project falls outside a fault rupture zone). A "No Impact" answer should be explained where it is based on general or project-specific factors (e.g., the project will not expose sensitive receptors to pollutants, based on a project-specific screening analysis). 2. All answers must consider the whole of the project-related effects, both direct and indirect, including off-site, cumulative, construction, and operational impacts. 3. Once the lead agency has determined that a particular physical impact may occur, the checklist answers must indicate whether that impact is potentially significant, less than significant with mitigation, or less than significant. "Potentially Significant Impact" is appropriate when there is sufficient evidence that a substantial or potentially substantial adverse change may occur in any of the physical conditions within the area affected by the project that cannot be mitigated below a level of significance. If there are one or more "Potentially Significant Impact" entries, an Environmental Impact Report (EIR) is required. 4. A "Mitigated Negative Declaration" (Negative Declaration: Less Than Significant with Mitigation Incorporated) applies where the incorporation of mitigation measures, prior to declaration of project approval, has reduced an effect from "Potentially Significant Impact" to a "Less Than Significant Impact with Mitigation." The lead agency must describe the mitigation measures and briefly explain how they reduce the effect to a less than significant level. 5. Earlier analyses may be used where, pursuant to the tiering, program EIR, or other CEQA process, an effect has been adequately analyzed in an earlier EIR (including a General Plan) or Negative Declaration [CCR, Guidelines for the Implementation of CEQA, § 15063(c)(3)(D)]. References to an earlier analysis should: a) Identify the earlier analysis and state where it is available for review. b) Indicate which effects from the environmental checklist were adequately analyzed in the earlier document, pursuant to applicable legal standards, and whether these effects were adequately addressed by mitigation measures included in that analysis. c) Describe the mitigation measures in this document that were incorporated or refined from the earlier document and indicate to what extent they address site-specific conditions for this project. 6. Lead agencies are encouraged to incorporate references to information sources for potential impacts into the checklist or appendix (e.g., general plans, zoning ordinances, biological assessments). Reference to a previously prepared or outside document should include an indication of the page or pages where the statement is substantiated. 7. A source list should be appended to this document. Sources used or individuals contacted should be listed in the source list and cited in the discussion. 8. Explanation(s) of each issue should identify: a) the criteria or threshold, if any, used to evaluate the significance of the impact addressed by each question; and, b) the mitigation measures, if any, prescribed to reduce the impact below the level of significance. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 19 of 100 4. Environmental Issues I. Aesthetics Environmental Setting The project site is located within the Historic Character Overlay District of Arroyo Grande (City of Arroyo Grande and Graves 2003). The project site is surrounded by Kiwanis Park recreational area to the east and a number of historic properties located north and south of the site, including the Arroyo Grande IOOF Hall (128 Bridge Street) and the Olohan Building (101 West Branch Street). Existing visual resources in the project area include views of the Arroyo Grande Creek riparian corridor, the adjacent Kiwanis Park, and the historic bridge and downtown Village. The existing bridge structure is built at grade, allowing views through the project site to both sides of the crossing. The only built details that extend upward into a potential line of sight are the pony trusses and walkway railings. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Have a substantial adverse effect on a scenic vista? b) Substantially damage scenic resources, including, but not limited to, trees, rock outcroppings, and historic buildings within a state scenic highway? c) Substantially degrade the existing visual character or quality of the site and its surroundings? d) Create a new source of substantial light or glare which would adversely affect day or nighttime views in the area? Discussion a) – c) For CEQA purposes, a scenic vista is generally defined as a viewpoint that provides expansive views of a highly valued landscape for the benefit of the general public. A substantial adverse effect on a scenic vista would occur if the proposed project would significantly degrade the scenic landscape as viewed from public roads or other public areas. The project site is located within an urbanized area comprised of development and infrastructure and is not considered a scenic vista. US 101, located 0.2 mile south of the project site, is designated as an “Eligible State Scenic Highway – Not Officially Listed” by the California Scenic Highway Mapping System. Views of the project site from US 101 are entirely obstructed by development within the city of Arroyo Grande. The proposed project would not substantially alter the visual character of the historic bridge and would not impact the two historic buildings within the vicinity of the site. There are no rock outcroppings or trees that are considered sensitive scenic resources in proximity of the site that would be significantly altered as a result of the proposed bridge rehabilitation. Visual quality of the project area is dominated by Arroyo Grande Creek, urban development, and road infrastructure. The project site is visible from Bridge Street, East Branch Street, Olohan Alley, and Nelson INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 20 of 100 Street. The number of viewers would be high due to high vehicular and pedestrian use within this area. Short-term construction activities would create visual impacts in the project area due to the presence of construction equipment, earthwork activities, detour signage, etc. However, these impacts would be temporary in nature and limited to the construction period. The project site would look similar to existing conditions once construction is complete. The rehabilitated bridge would also be built at grade and would not protrude into the skyline or block views due to a rise in elevation. The proposed project would be consistent with the historic character of the surrounding area and would not degrade existing views. Therefore, impacts would be less than significant. d) The existing bridge structure does not include lighting and the project would not propose the addition of any new lighting. Nighttime views in the vicinity of the project would not differ from existing conditions. Therefore, impacts would be less than significant. Mitigation Measures and Residual Impacts No significant impacts to aesthetic resources were identified; therefore, no mitigation measures are necessary. II. Agriculture and Forestry Resources Environmental Setting The U.S. Department of Agriculture Natural Resources Conservation Service (NRCS) classifies agricultural lands into five categories: Prime Farmland, Farmland of Statewide Importance, Unique Farmland, Farmland of Local Importance, and Farmland of Local Potential. Non-farmlands are classified as Grazing Land, Urban and Built-Up Land, Other Land, or Water. The project site is classified as “Urban and Built- Up Land” based on the California Department of Conservation’s (CDOC) Farmland Mapping and Monitoring Program (FMMP) and San Luis Obispo County Important Farmland Map (CDOC 2014). The Agriculture, Conservation, and Open Space Element of the City’s General Plan identifies the importance of avoiding and/or mitigating for the loss of prime farmland soils and of conserving non- prime agriculture uses and natural resource lands. The City’s policies also recognize the importance of allocation and conservation of ground and surface water resources for agricultural uses and the need to minimize potential urban and fringe area development that would divert such resources away from agricultural uses. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Convert Prime Farmland, Unique Farmland, or Farmland of Statewide Importance (Farmland), as shown on the maps prepared pursuant to the Farmland Mapping and Monitoring Program of the California Resources Agency, to non-agricultural use? INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 21 of 100 Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact b) Conflict with existing zoning for agricultural use or a Williamson Act contract? c) Conflict with existing zoning for, or cause rezoning of, forest land (as defined in Public Resources Code section 12220)g)), timberland (as defined by Public Resources Code section 4526), or timberland zoned Timberland Production (as defined by Government Code section 51104(g))? d) Result in the loss of forest land or conversion of forest land to non-forest use? e) Involve other changes in the existing environment which, due to their location or nature, could result in conversion of Farmland to non-agricultural use? * In determining whether impacts to agricultural resources are significant environmental effects, lead agencies may refer to the California Agricultural Land Evaluation and Site Assessment Model (1997), prepared by the California Department of Conservation as an optional model for use in assessing impacts on agricultural and farmland. Discussion a) – d) The project site is within the Village Core land use designation and is designated as Urban and Built Up Land. The project site does not contain any Prime Farmland, Unique Farmland, or Farmland of Statewide or Local Importance; no direct effect on these resources would occur. There are no active agricultural lands within the project area and no direct conversion of Prime agricultural land would occur as a result of the project. No indirect impacts on off-site agriculturally productive parcels would occur due to the distance of any such parcel. No portion of the project area is currently subject to a Williamson Act contract or agricultural preserve program. Due to the distance of any proximate Williamson Act contracted lands or agricultural preserves, the project would not conflict with or indirectly affect lands subject to an agricultural preserve program. There is no forestland in San Luis Obispo County and no impacts to forestland or timberland would occur. No impacts would occur. e) The project would rehabilitate an existing bridge along its existing alignment. Bridge rehabilitation would not result in other changes to the environment that would indirectly result in a loss or conversion of agricultural land. Therefore, impacts would be less than significant. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 22 of 100 Mitigation Measures and Residual Impact No significant impacts to agricultural resources were identified; therefore, no mitigation measures are necessary. III. Air Quality Environmental Setting San Luis Obispo County is part of the South Central Coast Air Basin, which also includes Santa Barbara and Ventura Counties. The climate of the basin area is strongly influenced by its proximity to the Pacific Ocean. Airflow around and within the basin plays an important role in the movement and dispersion of pollutants. The speed and direction of local winds are controlled by the location and strength of the Pacific High pressure system and other global weather patterns, topographical factors, and circulation patterns that result from temperature differences between the land and the sea. The San Luis Obispo County Air Pollution Control District (APCD) has developed and updated their CEQA Air Quality Handbook (APCD 2012) to evaluate project-specific impacts and help determine if air quality mitigation measures are needed, or if potentially significant impacts could result. To evaluate long-term emissions, cumulative effects, and establish countywide programs to reach acceptable air quality levels, the APCD has prepared and adopted a Clean Air Plan. The County’s air quality is measured by multiple ambient air quality monitoring stations, including four APCD-operated permanent stations, two state-operated permanent stations, two special stations, and one station operated by Tosco Oil Refinery for monitoring Sulfur Dioxide (SO2) emissions. San Luis Obispo County is in non-attainment status for ozone (O3), respirable particulate matter (PM10) and vinyl chloride under the California Air Resource Board (CARB) standards. The county is in attainment status for all other applicable CARB standards. The project site is not within an area identified as having a potential for Naturally Occurring Asbestos (NOA) to occur based on the APCD’s NOA Map (APCD 2017). Some land uses are considered more sensitive to changes in air quality than others, depending on the population groups and the activities involved. The CARB has identified the following typical groups who are most likely to be affected by air pollution: children under 14 years of age, the elderly over 65 years of age, athletes, and people with cardiovascular and chronic respiratory diseases. Sensitive receptors include residences, schools, playgrounds, childcare centers, athletic facilities, long-term health care facilities, rehabilitation centers, convalescent centers, and retirement homes. Sensitive receptors near the project area include nearby residences, Kiwanis Park, and various commercial uses associated with the City’s Village Core where children or elderly may visit, including the Saturday Farmer’s Market hosted in Olohan Alley. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Conflict with or obstruct implementation of the applicable air quality plan? INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 23 of 100 Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact b) Violate any air quality standard or contribute substantially to an existing or projected air quality violation? c) Result in a cumulatively considerable net increase of any criteria pollutant for which the project region is in non-attainment under an applicable federal or state ambient air quality standard (including releasing emissions which exceed quantitative thresholds for ozone precursors)? d) Expose sensitive receptors to substantial pollutant concentrations? e) Create objectionable odors affecting a substantial number of people? * Where available, the significance criteria established by the applicable air quality management or air pollution control district may be relied on to make these determinations. Discussion a) The project would rehabilitate and improve existing infrastructure and does not propose a new or increased use in the project area. The proposed use is consistent with existing land uses and the general level of development anticipated and projected in the Clean Air Plan as well as other applicable regional and local planning documents. The proposed project would not conflict with or otherwise obstruct implementation of the Clean Air Plan. Impacts would be less than significant. b) – d) Construction Impacts. During construction, short-term degradation of air quality may occur due to the release of particulate matter (airborne dust) and other pollutants generated by excavation, grading, demolition, hauling, and various other activities related to construction. Site preparation and roadway/bridge construction would involve clearing, cut-and-fill activities, grading, removing or improving existing roadways, and paving roadway surfaces. Specifically, Abutment #1, located on the north side of Arroyo Grande Creek would require 689 cubic yards of rock slope protection (RSP), 396 cubic yards of cut, and 24 cubic yards of fill material. Abutment #2, located on the south side of Arroyo Grande Creek, would require 754 cubic yards of RSP, 74 cubic yards of cut, and 429 cubic yards of fill. This would result in the generation of construction dust as well as short- and long-term construction vehicle emissions, including diesel particulate matter (DPM), reactive organic gases (ROG), oxides of nitrogen (NOx), particulate matter (PM), and greenhouse gas (GHG) emissions. Construction activities would be limited in scale (bridge rehabilitation) and duration (approximately 8 months). The project site consists of approximately 2 acres. The area of proposed disturbance is less than 4 acres, which the APCD has identified as the amount of disturbance that can exceed the 2.5-ton PM10 (particulate matter less than 10 micrometers in diameter) threshold. Specific construction equipment and information is not yet known. Based on screening emission rates for construction activities INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 24 of 100 identified in Table 2.2 of the CEQA Air Quality Handbook, the project is anticipated to generate the following emissions included in Table 2. Table 2. Estimated Construction-Related Emissions Pollutant Estimated Emissions Applicable APCD Threshold Within Threshold? Diesel Particulate Matter (DPM) 0.003 ton 0.13 tons Yes Reactive Organic Gases (ROG) 0.01 ton 2.5 tons (combined) Yes Oxides of Nitrogen (NOx) 0.002 ton The project is within applicable thresholds for construction-related emissions. However, the project is in close proximity to a limited number of sensitive receptors (i.e., park, visitor-serving uses in immediate surrounding areas). Standard diesel idling restrictions and mitigation measures for construction equipment and fugitive dust would apply to reduce any potentially significant impacts related to exposure of sensitive receptors to harmful construction vehicle emissions and/or fugitive dust. Therefore, construction-related impacts would be less than significant with mitigation. Operational Impacts. From an operational standpoint, the project would not change air quality from existing conditions. No increase in traffic trips or point source emissions would be generated by the proposed bridge rehabilitation. Therefore, no significant long-term operational impacts would occur. Operational impacts would be less than significant. Exposure to Pollutants. Naturally Occurring Asbestos (NOA) has been identified as a toxic air contaminant by the CARB. Any ground disturbance proposed in an area identified as having the potential to contain NOA must comply with the CARB Airborne Toxics Control Measure (ATCM) for Construction, Grading, Quarrying, and Surface Mining Operations. The APCD NOA Map indicates that the project site is not within an area identified as having a potential for NOA to occur (APCD 2017). Therefore, impacts would be less than significant. e) Construction of the proposed project would generate odors associated with construction smoke/dust and equipment exhaust and fumes. Excavated and demolition materials may also contain objectionable odors within unearthed materials. The proposed construction activities would not differ significantly from those resulting from any other type of construction project. Any effects would be short-term in nature and limited to the construction phase of the project. Therefore, the project would not create objectionable odors affecting a substantial number of people. Impacts would be less than significant. Mitigation Measures and Residual Impact To minimize the potential significant impacts to air quality, the following mitigation measures would be implemented. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 25 of 100 AQ/mm-1 Prior to issuance of construction permits, the following measures shall be incorporated into the construction phase of the project and shown on all applicable plans: Construction Equipment a. Maintain all construction equipment in proper tune according to manufacturer’s specifications; b. Fuel all off-road and portable diesel powered equipment with California Air Resources Board-certified motor vehicle diesel fuel (non-taxed version suitable for use off-road); c. Use diesel construction equipment meeting the California Air Resources Board’s Tier 2 certified engines or cleaner off-road heavy-duty diesel engines, and comply with the State off-Road Regulation; d. Use on-road heavy-duty trucks that meet the California Air Resources Board’s 2007 or cleaner certification standard for on-road heavy-duty diesel engines, and comply with the State On-Road Regulation; e. Construction or trucking companies with fleets that that do not have engines in their fleet that meet the engine standards identified in the above two measures (e.g., captive or oxides of nitrogen exempt area fleets) may be eligible by proving alternative compliance; f. All on- and off-road diesel equipment shall not idle for more than 5 minutes. Signs shall be posted in the designated queuing areas and or job sites to remind drivers and operators of the 5-minute idling limit; g. Diesel idling shall be avoided to the greatest extent feasible throughout the duration of construction activities. No idling in excess of 5 minutes shall be permitted as described above; h. Staging and queuing areas shall not be located within 1,000 feet of sensitive receptors whenever possible; i. Electrify equipment when feasible; j. Substitute gasoline-powered in place of diesel-powered equipment, where feasible; and, k. Use alternatively fueled construction equipment on-site where feasible, such as compressed natural gas (CNG), liquefied natural gas (LNG), propane, or biodiesel. AQ/mm-2 Upon application for construction permits, all required PM10 measures shall be shown on applicable grading or construction plans, and made applicable during grading and construction activities as described below. a. Reduce the amount of the disturbed area where possible; b. Use of water trucks or sprinkler systems in sufficient quantities to prevent airborne dust from leaving the site and from exceeding the San Luis Obispo County Air Pollution Control District’s limit of 20% opacity for greater than 3 minutes in any 60-minute INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 26 of 100 period. Increased watering frequency would be required whenever wind speeds exceed 15 miles per hour. Reclaimed (non-potable) water should be used whenever possible; c. All dirt stock pile areas should be sprayed daily or covered with tarps or other dust barriers, as needed; d. Permanent dust control measures identified in the approved project revegetation and landscape plans should be implemented as soon as possible following completion of any soil-disturbing activities; e. Exposed ground areas that are planned to be reworked at dates greater than 1 month after initial grading should be sown with a fast germinating, non-invasive grass seed and watered until vegetation is established; f. All disturbed soil areas not subject to revegetation should be stabilized using approved chemical soil binders, jute netting, or other methods approved in advance by the San Luis Obispo County Air Pollution Control District; g. All roadways, driveways, sidewalks, etc. to be paved should be completed as soon as possible. In addition, building pads should be laid as soon as possible after grading unless seeding or soil binders are used; h. Vehicle speed for all construction vehicles shall not exceed 15 miles per hour on any unpaved surface at the construction site; i. All trucks hauling dirt, sand, soil, or other loose materials are to be covered or should maintain at least 2 feet of freeboard (minimum vertical distance between top of load and top of trailer) in accordance with California Vehicle Code Section 23114; j. Install wheel washers or other devices to control tracking of mud and dirt onto adjacent roadways where vehicles enter and exit unpaved roads onto streets, or wash off trucks and equipment leaving the site; k. Sweep streets at the end of each day if visible soil material is carried onto adjacent paved roads. Water sweepers with reclaimed water should be used where feasible. Roads shall be pre-wetted prior to sweeping when feasible; l. The contractor or builder shall designate a person or persons to monitor the fugitive dust emissions and enhance the implementation of the measures as necessary to minimize dust complaints, reduce visible emissions below the San Luis Obispo County Air Pollution Control District’s limit of 20% opacity for greater than 3 minutes in any 60-minute period, and to prevent transport of dust off-site. Their duties shall include holidays and weekend periods when work may not be in progress. The name and telephone number of such persons shall be provided to the San Luis Obispo County Air Pollution Control District Engineering & Compliance Division prior to the start of any grading, earthwork, or demolition. With the incorporation of these measures, residual impacts to air quality would be less than significant. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 27 of 100 IV. Biological Resources Environmental Setting The following section is based largely on the Natural Environment Study (NES) prepared for the project (SWCA 2017a). The project area includes 250 linear feet along Bridge Street between Olohan Alley and Nelson Street and approximately 515 linear feet of the Arroyo Grande Creek corridor. The project site encompasses the bridge, Arroyo Grande Creek, existing surface parking areas, and sidewalks, as well as ruderal areas within Kiwanis Park. The project area supports two sensitive natural communities: Arroyo Willow Thicket and habitat for South-Central California Coast steelhead. Other vegetation communities observed within the site include ornamental plantings, ruderal, and developed landscapes. Riparian Habitat/Jurisdictional Wetlands Arroyo Grande Creek is a perennial stream that flows directly into the Pacific Ocean. Arroyo Grande Creek maintains definable Ordinary High Water Marks (OHWMs), supports riparian vegetation, and has bed and bank features. Even though the surrounding area is subject to constant disturbance from urban influences, the creek is relatively undisturbed due to the incised nature of the channel. The riparian system serves as a valuable wildlife habitat and an important water supply feature. Approximately 0.16 acre of the project site has been identified as U.S. Army Corps of Engineers (USACE) jurisdictional “other waters” and approximately 1.25 acres are identified as state jurisdictional features (SWCA 2017b). These areas include the riparian corridor of Arroyo Grande Creek that traverse the project site. The Regional Water Quality Control Board (RWQCB) also asserts jurisdiction over waters of the State, through the Porter Cologne Act. Wildlife Corridors The project site does not fall within an Essential Connectivity Area. However, the Arroyo Grande Creek riparian corridor within the project site may be used by wildlife as a movement corridor on a smaller scale since the Arroyo Grande Creek riparian corridor provides habitat for many species. Special-Status Species Based on an online query of the California Natural Diversity Database (CNDDB), a total of 30 special- status plant species, 29 special-status animal species, and 5 sensitive habitats were analyzed for potential to occur within the project area. Of the species analyzed, four special-status plant species, five special-status wildlife species, and two sensitive wildlife groups were determined to have potential to occur within the project area: • Gambel’s watercress (Nasturtium gambelii) • black-flowered figwort (Scrophularia atrata) • San Bernardino aster (Symphyotrichum defoliatum) • marsh sandwort (Arenaria paludicola) • monarch butterfly (Danaus plexippus) • South-Central California Coast steelhead DPS (Oncorhynchus mykiss) • California red-legged frog (Rana draytonii) • western pond turtle (Emys marmorata) • nesting migratory birds • Townsend’s big-eared bat (Corynorhinus townsendii) and other roosting bats INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 28 of 100 Botanical surveys conducted during the appropriate flowering season did not identify the presence of any sensitive plant species. No identified steelhead or California red-legged frog were identified during field surveys; however, their presence is inferred based on their well-known occurrences in Arroyo Grande Creek. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Have a substantial adverse effect, either directly or through habitat modification, on any species identified as a sensitive, candidate, or special status species in local or regional plans, policies, or regulations, or by the California Department of Fish and Wildlife or the U.S. Fish and Wildlife Service? b) Have a substantial adverse effect on any riparian habitat or other sensitive natural community identified in local or regional plans, policies, or regulations, or by the California Department of Fish and Wildlife or the U.S. Fish and Wildlife Service? c) Have a substantial adverse effect on federally protected wetlands, as defined by §404 of the Clean Water Act (including, but not limited to, marsh, vernal pool, coastal, etc.) through direct removal, filling, hydrological interruption, or other means? d) Interfere substantially with the movement of any native resident or migratory fish or wildlife species or with established native resident or migratory wildlife corridors, or impede the use of native wildlife nursery sites? e) Conflict with any local policies or ordinances protecting biological resources, such as a tree preservation policy or ordinance? f) Conflict with the provisions of an adopted Habitat Conservation Plan, Natural Community Conservation Plan, or other approved local, regional, or state habitat conservation plan? Discussion a) Plant Species. The project area provides suitable habitat for four sensitive plant species: Gambel’s watercress, black-flowered figwort, San Bernardino aster, and marsh sandwort. However, these sensitive plant species were not observed during field surveys and no impacts to these sensitive plant species are expected to occur. Wildlife Species. Focused surveys for South-Central California Coast steelhead were not conducted. However, the project site is within the Arroyo Grande Creek watershed and supports a known steelhead INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 29 of 100 population. Therefore, presence of South-Central California Coast steelhead is inferred within the project area. If present within the project site during project activities, individual steelhead may be directly impacted. They may be stranded in portions of the creek that must be dewatered, become caught in dewatering pumps, or made vulnerable to predation from foraging birds and mammals. With the implementation of avoidance and minimization measures included below, these direct impacts may be avoided. Potential indirect impacts to steelhead from the project may also occur. Indirect impacts include sediment deposition downstream of the work area, which may adversely impact downstream water quality. Indirect impacts to steelhead may be avoided through the use of appropriate silt and erosion control measures. No protocol surveys were conducted for California red-legged frog and the species was not observed during reconnaissance surveys. However, suitable in-stream aquatic habitat is present within the project site and, based on previous known occurrences, the presence of the California red-legged frog within the project area is inferred. Project construction could result in the injury or mortality of California red- legged frogs (if present) during diversion/dewatering of Arroyo Grande Creek. The potential need to capture and relocate California red-legged frogs could subject these animals to stresses that could result in adverse effects. Injury or mortality could occur via accidental crushing by worker foot-traffic or construction equipment. Erosion and sedimentation could also occur, which could directly or indirectly affect water quality. An unknown number of California red-legged frogs could be subjected to take, but the potential for these impacts is anticipated to be low due to no observations of the species within the project site during surveys. However, this could change with time, where habitat conditions and/or California red-legged frog numbers could fluctuate. The avoidance and minimization measures described below would be required to reduce potential impacts to the red-legged frog to less than significant. No western pond turtles were observed during surveys. Suitable aquatic habitat occurs within the project site for this species and there is a CNDDB occurrence record (CNDDB Occ. 1165) for western pond turtle in Arroyo Grande Creek approximately 0.5 mile north of the project site. Presence of western pond turtle is inferred within the project site. Similar to the impacts described previously for California red-legged frog, project construction could result in the injury or mortality of western pond turtle during diversion/dewatering. The potential need to capture and relocate these species would subject individuals to stresses that could result in adverse effects. Injury or mortality could occur via accidental crushing by worker foot-traffic or construction equipment. Erosion and sedimentation could also occur, which would directly or indirectly affect water quality. The potential for these impacts is anticipated to be low due to no observations of the species during surveys. Mitigation and avoidance measures included below would reduce impacts to the western pond turtle to less than significant. Riparian habitat within the project site may provide suitable foraging habitat for least Bell’s vireo and southwestern willow flycatcher. Nesting pairs of both of these species are considered unlikely, but cannot be ruled out due to the presence of suitable riparian habitat. While no specific nesting migratory bird surveys were conducted, it is inferred that nesting migratory birds would exist within the creek corridor or on the bridge itself. The removal of vegetation could directly impact active bird nests and any eggs or young residing in nests. Indirect impacts could also result from noise and disturbance associated with construction, which could alter perching, foraging, and/or nesting behaviors. While temporary loss of vegetation supporting potential nesting habitat would occur, this would be mitigated by habitat restoration. The implementation of the avoidance and minimization measures such as appropriate timing of vegetation removal, pre-activity surveys, and exclusion zones would reduce the potential for adverse effects to nesting bird species. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 30 of 100 No bats or evidence of bat activity were observed beneath the Bridge Street Bridge or within the project site during the field surveys. However, the existing bridge and the riparian vegetation may support suitable roosting habitat or structure for bat species. If bats utilized the bridge or surrounding trees for seasonal roosting, then direct impacts to bats could result during the proposed rehabilitation of the bridge. These direct effects could result in the injury or mortality of bats or harassment that could alter roosting behaviors. Indirect impacts could also result from noise and disturbance associated with construction, which could also alter roosting behaviors. Implementation of pre-activity surveys and exclusionary netting would reduce the potential for adverse effects to roosting bat species. No impacts to Townsend’s big-eared bat and other roosting bats are anticipated with implementation of the avoidance and minimization measures included below. Therefore, potential impacts to sensitive species would be less than significant with mitigation. b) The proposed project has the potential to impact areas associated with the Arroyo Grande Creek riparian corridor within the project area. The project site supports sensitive natural communities associated with riparian habitats, including Arroyo Willow Thicket. Temporary impacts would occur within the areas that include the dewatering/diversion structure, slopes and areas that will be revegetated, and associated riparian vegetation removal. Project staging areas have been selected to minimize unnecessary impacts to native riparian vegetation. It is anticipated that the proposed project would result in both temporary and permanent impacts to Arroyo Willow Thicket. Implementation of Best Management Practices (BMPs) for erosion and sediment control, the use of fencing exclusion zones for environmentally sensitive areas, preparation of a spill prevention and containment plan for hazardous materials, and the use erosion controls and monitoring during construction would reduce impacts to sensitive communities associated with the Arroyo Grande Creek riparian corridor. Impacted riparian vegetation would also be restored upon completion of construction activities. The project also has the potential to impact critical habitat for South-Central California Coast steelhead. Arroyo Grande Creek is within the South-Central California Coast steelhead Distinct Population Segment (DPS) Estero Bay Hydrologic Unit 3310 and Oceano Hydrologic Sub-area 331031. Following a status review in 2005, a final listing determination was issued on January 5, 2006, for the South-Central California Coast steelhead DPS, and critical habitat was designated within 32 DPS watersheds, including the Arroyo Grande Creek watershed (National Oceanic and Atmospheric Administration National Marine Fisheries Service [NOAA Fisheries] 2011). Essential spawning sites, rearing sites, suitable water quality, migration corridors, and proper estuarine parameters are typical of this critical habitat designation. The proposed project would result in temporary impacts to open water within Arroyo Grande Creek. Mitigation measures described below would be required to minimize effects on the riparian habitat and steelhead critical habitat within the project area. Therefore, impacts on riparian and sensitive habitat areas would be less than significant with mitigation. c) The project area contains features that are subject to USACE, California Department of Fish and Wildlife (CDFW), and RWQCB jurisdiction due to a presence of a clear OHWM, the evidence of a defined bed and bank, connectivity to relatively permanent waters, presence of riparian vegetation, and evidence of wetland hydrology. Approximately 0.16 acre of the project area falls under federal jurisdiction (Clean Water Act, Sections 401 and 404) and approximately 1.25 acres of the project area are under state jurisdiction (Porter Cologne Act, CDFW Sections 1600–1602) (SWCA 2017b). The proposed project would result in both temporary and permanent impacts to jurisdictional waters. Temporary impacts would occur within the areas that include the dewatering/diversion structure, slopes INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 31 of 100 and areas that will be revegetated, and associated riparian vegetation removal. Approximately 0.13 acre of temporary impacts to federal jurisdictional areas and 0.57 acre of temporary impacts to state jurisdictional areas would occur. Project staging areas have been selected to minimize unnecessary impacts to native riparian vegetation. Temporarily impacted areas are expected to be returned to the pre-construction condition following project completion. Permanent impacts would result from construction of the new substructure and new pier within the Arroyo Grande Creek channel. Approximately 0.18 acre of permanent impacts would occur to state jurisdictional areas. No federal wetlands or other isolated or adjacent wetland areas were delineated within the project area. The project area does not occur within the Coastal Zone, so a one-parameter wetland delineation is not necessary for compliance with the California Coastal Act. The project is not expected to impact jurisdictional wetlands, but may impact other waters of the U.S. Mitigation measures described below have been identified to reduce potential impacts. Potential impacts would be less than significant with mitigation. d) The project site does not fall within an Essential Connectivity Area. It is assumed that the riparian corridor within the project site may be used by wildlife as movement corridors on a smaller scale as the Arroyo Grande Creek riparian corridor provides habitat for many species. There are no known fish passage issues within the site. The nearest known fish passage issue is located at the Arroyo Grande Creek stream gauging station approximately 0.5 mile upstream from the project site. The project area would be restored and revegetated at the conclusion of construction activities and no permanent impacts on movement corridors would occur. Therefore, potential impacts would be less than significant. e) The City has coordinated with the U.S. Fish and Wildlife Service (USFWS), NOAA Fisheries, and CDFW, and has implemented mitigation measures designed to avoid existing marginal habitat areas and resources to the extent possible. The project would not interfere with the natural function of project area habitats, and disturbed areas would be restored after project construction. Therefore, the project would not be in conflict with any applicable policies protecting biological resources or environmentally sensitive habitats. Impacts would be less than significant. f) The project is not within an adopted Habitat Conservation Plan (HCP), Natural Community Conservation Plan, or other HCPs. No impacts would occur. Mitigation Measures and Residual Impact To minimize the potential significant impacts to biological resources, the following mitigation measures would be implemented. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 32 of 100 Jurisdictional Waters and Sensitive Habitats BIO/mm-1 Prior to construction, the City of Arroyo Grande Public Works Department will obtain a Section 404 Permit from the United States Army Corps of Engineers, a Section 401 Water Quality Certification from the Regional Water Quality Control Board, and a Section 1602 Streambed Alteration Agreement from the California Department of Fish and Wildlife for project- related impacts that will occur in areas under federal and state jurisdiction. BIO/mm-2 Prior to construction, the City of Arroyo Grande Public Works Department will retain a qualified biological monitor(s) to monitor construction and ensure compliance with the avoidance and minimization efforts outlined within all the project environmental documents. At a minimum, monitoring will occur during initial ground disturbance activities and vegetation removal within the Arroyo Grande Creek corridor. Monitoring may be reduced to part time once initial disturbance and vegetation removal activities are complete. The duration of monitoring should be at least once per week throughout the remaining construction phases, unless specified otherwise by permitting agencies. BIO/mm-3 Prior to construction, all construction personnel will participate in an environmental awareness training program conducted by a qualified biologist. At a minimum, the program shall include: descriptions of the special-status species that have potential to occur in the project area; their habitat requirements and life histories as they relate to the project; the avoidance, minimization, and mitigation measures that will be implemented to avoid impacts to the species and their habitats; the regulatory agencies and regulations that manage their protection; and consequences that may result from unauthorized impacts or take of special- status species and their habitats. Subsequent trainings shall be provided as needed for additional construction workers through the duration of construction activities. Subsequent trainings shall include, at minimum, a review of the training materials (i.e., a PowerPoint presentation or handouts prepared by the qualified biologist) and a signed acknowledgement that the construction worker has reviewed and understands the training materials. The training materials shall identify an on-site primary point of contact for all questions related to the environmental awareness training and actions required under the training program and shall include contact information for that primary on-site contact. BIO/mm-4 Construction activities within jurisdictional areas will be conducted during the dry season when stream flows will be at annual lows (June 15 through October 31) in any given year, or as otherwise directed by the regulatory agencies. Deviations from this work window can be made with permission from the relevant regulatory agencies. BIO/mm-5 Prior to initiation of any construction activities, including vegetation clearing or grubbing, sturdy high-visibility fencing will be installed to protect the jurisdictional areas adjacent to the designated work areas. This fencing will be placed so that unnecessary adverse impacts to the adjacent habitats are avoided. No construction work (including storage of materials) will occur outside of the specified project limits. The fencing will remain in place during the entire construction period, be monitored periodically by a qualified biologist, and be maintained as needed by the contractor. BIO/mm-6 Prior to construction, a Storm Water Pollution Prevention Plan will be prepared for the project. Provisions of this plan will be implemented during and after construction. Construction personnel will be informed of the importance of preventing spills, the appropriate INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 33 of 100 measures to take should a spill occur, and the measures necessary to avoid and minimize erosion and stormwater pollution in and near the work area. BIO/mm-7 Prior to construction, the contractor will prepare a Hazardous Materials Response Plan to allow for a prompt and effective response to any accidental spills. Workers will be informed of the importance of preventing spills and of the appropriate measures to take should a spill occur. BIO/mm-8 During construction, erosion control measures (e.g., silt fencing, fiber rolls, barriers) will remain available on-site and will be utilized as necessary to prevent erosion and sedimentation in jurisdictional areas. No synthetic plastic mesh products will be used for erosion control and use of these materials on-site is prohibited. Erosion control measures and other suitable Best Management Practices used will be checked to ensure that they are intact and functioning effectively and maintained on a daily basis throughout the duration of construction. The contractor will also apply adequate dust control techniques, such as site watering, during construction to protect water quality. BIO/mm-9 During construction, the cleaning and refueling of equipment and vehicles will occur only within a designated staging area and at least 60 feet (20 meters) from jurisdictional other waters or other aquatic areas. At a minimum, equipment and vehicles will be checked and maintained on a daily basis to ensure proper operation and avoid potential leaks or spills. BIO/mm-10 During construction, trash will be contained, removed from the work site, and disposed of regularly. Following construction, trash and construction debris will be removed from the work areas. Vegetation removed from the construction site will be taken to a certified landfill to prevent the spread of invasive species. If soil from weedy areas (such as areas with poison hemlock or other invasive exotic plant species) must be removed off-site, the top 6 inches (152 millimeters) containing the seed layer in areas with weedy species will be disposed of at a permitted landfill. BIO/mm-11 During construction, no pets will be allowed on the construction site. BIO/mm-12 Prior to construction, the City of Arroyo Grande Public Works Department will prepare a comprehensive Habitat Mitigation and Monitoring Plan that provides for a 1:1 restoration ratio for temporary impacts and a 3:1 enhancement ratio for permanent impacts, unless otherwise directed by regulatory agencies. To the extent feasible, mitigation activities will be implemented within the project area and/or the Arroyo Grande Creek riparian corridor and in areas in and adjacent to the project area that support exotic species, contain agricultural trash, and have erosion. These areas provide the most optimal mitigation opportunities on-site. Any revegetation will be conducted using only native plant species. The final Habitat Mitigation and Monitoring Plan will identify the specific mitigation sites and it will be implemented immediately following project completion. BIO/mm-13 During construction, the project will make all reasonable efforts to limit the use of imported soils for fill. Soils currently existing on-site should be used for fill material. If the use of imported fill material is necessary, the imported material must be obtained from a source that is known to be free of invasive plant species, or the material must consist of purchased clean material such as crushed aggregate, sorted rock, or similar. To avoid the spread of invasive species, the contractor shall: INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 34 of 100 a. Stockpile topsoil and redeposit the stockpiled soil on-site at a sufficient depth to preclude germination or spread of those species after construction is complete; or, b. Transport the topsoil to a permitted landfill for disposal. BIO/mm-14 Prior to construction, project plans will clearly identify the type of species, location, and methodology of removal and disposal of invasive exotic species found within the project site. Removal and disposal of invasive exotic plants and wildlife must be in accordance with state law and/or project authorizations from resource agencies (e.g., USFWS Programmatic Biological Opinion). In particular, for those invasive exotic plant species that are particular difficult to remove (e.g., jubata grass [Cortaderia jubata]), a combination of cutting and application of herbicide would likely be required, and thus require a request for an amendment to the standard conditions of the USFWS Programmatic Biological Opinion. In addition, removal of crayfish or bullfrog must be conducted lawfully using methodologies outlined in the California Fish and Game Code. BIO/mm-15 During construction, the biological monitor(s) will ensure that the spread or introduction of invasive exotic plant and wildlife species is avoided to the maximum extent possible. BIO/mm-16 All erosion control materials including straw bales, straw wattles, or mulch used on-site must be free of invasive species seed. South-Central California Coast Steelhead BIO/mm-17 In-stream work will take place between June 15 and October 31 in any given year, when the surface water within Arroyo Grande Creek is likely to be at seasonal minimum. Deviations from this work window will only be made with permission from the relevant regulatory agencies. During in-stream work, a qualified biologist that is approved by the National Oceanic and Atmospheric Administration National Marine Fisheries Service and has experience in steelhead biology and ecology, aquatic habitats, biological monitoring (including diversion/dewatering), and capturing, handling, and relocating fish species will be retained. During in-stream work, the biological monitor(s) will continuously monitor placement and removal of any required stream diversions and will capture stranded steelhead and other native fish species and relocate them to suitable habitat, as appropriate. The approved biologist(s) will capture steelhead stranded as a result of diversion/dewatering and relocate steelhead to the nearest suitable in-stream habitat. The approved biologist(s) will note the number of steelhead observed in the affected area, the number of steelhead relocated, and the date and time of the collection and relocation. BIO/mm-18 During in-stream work, if pumps are incorporated to assist in temporarily dewatering the site, intakes will be completely screened with no larger than 0.2-inch (5- millimeter) wire mesh to prevent steelhead and other sensitive aquatic species from entering the pump system. Pumps will release the diverted water so that suspended sediment will not re- enter the stream. The form and function of pumps used during the dewatering activities will be checked daily, at a minimum, by a qualified biological monitor to ensure a dry work environment and minimize adverse effects to aquatic species and habitats. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 35 of 100 California Red-Legged Frog BIO/mm-19 Only United States Fish and Wildlife Service-approved biologists will participate in activities associated with the capture and handling of California red-legged frogs. Biologists authorized under the Programmatic Biological Opinion do no need to resubmit their qualifications for subsequent projects conducted pursuant to the Programmatic Biological Opinion, unless the United States Fish and Wildlife have revoked their approval at any time during the life of the Programmatic Biological Opinion. BIO/mm-20 Ground disturbance will not begin until written approval is received from the United States Fish and Wildlife Service that the biologist(s) is qualified to conduct the work. The California Department of Transportation will request approval of the biologist(s) from the United States Fish and Wildlife Service. BIO/mm-21 A United States Fish and Wildlife Service-approved biologist will survey the project area no more than 48 hours before the onset of work activities. If any life stage of the California red-legged frog is found and these individuals are likely to be killed or injured by work activities, the approved biologist will be allowed sufficient time to move them from the site before work activities begin. The United States Fish and Wildlife Service-approved biologist will relocate the California red-legged frogs the shortest distance possible to a location that contains suitable habitat and will not be affected by the activities associated with the project. The relocation site should be in the same drainage to the extent practicable. The California Department of Transportation will coordinate with the United States Fish and Wildlife Service on the relocation site prior to the capture of any California red-legged frogs. BIO/mm-22 A United States Fish and Wildlife Service-approved biologist will be present at the work site until California red-legged frogs have been relocated out of harm’s way, workers have been instructed, and disturbance of the habitat has been completed. After this time, the City of Arroyo Grande Public Works Department will designate a person to monitor on-site compliance with minimization measures. The United States Fish and Wildlife Service-approved biologist will ensure that this monitor receives the training outlined in BIO/mm-3 above and in the identification of California red-legged frogs. If the monitor or the United States Fish and Wildlife Service-approved biologist recommends that work be stopped because California red- legged frogs would be affected in any manner, they will notify the resident engineer (the engineer that is directly overseeing and in command of construction activities) immediately. The resident engineer will either resolve the situation by eliminating the adverse effect immediately or require that actions that are causing these effects be halted. If work is stopped, the California Department of Transportation, City of Arroyo Grande Public Works Department, and United States Fish and Wildlife Service will be notified as soon as is reasonably possible. BIO/mm-23 During project activities, trash that may attract predators will be properly contained, removed from the work site, and disposed of regularly. Following construction, trash and construction debris will be removed from work areas. BIO/mm-24 All refueling, maintenance, and staging of equipment and vehicles will occur at least 60 feet from riparian habitat or water bodies and in a location from where a spill would not drain directly toward aquatic habitat (e.g., on a slope that drains away from the water). The monitor will ensure contamination of habitat does not occur during such operations. Prior to the onset of work, the City of Arroyo Grande Public Works Department will ensure that a plan is in INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 36 of 100 place for prompt and effective response to any accidental spills. All workers will be informed of the importance of preventing spills and of the appropriate measures to take should a spill occur. BIO/mm-25 Habitat contours will be returned to their original configuration at the end of project activities. This measure will be implemented in all areas disturbed by activities associated with the project, unless the United States Fish and Wildlife, California Department of Transportation, and City of Arroyo Grande Public Works Department determine that it is not feasible or modification of original contours would benefit the California red-legged frog. BIO/mm-26 The number of access routes, size of staging areas, and the total area of activity will be limited to the minimum necessary to achieve the project. Environmentally Sensitive Areas will be established to confine access routes and construction areas to the minimum area necessary to complete construction, and minimize the impact to California red-legged frog habitat; this goal includes locating access routes and construction areas outside of wetlands and riparian areas to the maximum extent practicable. BIO/mm-27 The City of Arroyo Grande Public Works Department will attempt to schedule work for times of the year when impacts to the California red-legged frog would be minimal. For example, work that would affect large pools that may support breeding would be avoided, to the maximum degree practicable, during the breeding season (November through May). Isolated pools that are important to maintain California red-legged frogs through the driest portions of the year would be avoided, to the maximum degree practicable, during the late summer and early fall. Habitat assessments, surveys, and technical assistance between the California Department of Transportation and United States Fish and Wildlife Service during project planning will be used to assist in scheduling work activities to avoid sensitive habitats during key times of year. BIO/mm-28 To control sedimentation during and after project implementation, the City of Arroyo Grande Public Works Department will implement Best Management Practices outlined in any authorizations or permits issued under the authorities of the Clean Water Act that it receives for the specific project. BIO/mm-29 If a work site is to be temporarily dewatered by pumping, intakes will be completely screened with wire mesh not larger than 0.2 inch to prevent California red-legged frogs from entering the pump system. Water will be released downstream at an appropriate rate to maintain downstream flows during construction. Upon completion of construction activities, any diversions or barriers to flow will be removed in a manner that would allow flow to resume with the least disturbance to the substrate. Alteration of the streambed will be minimized to the maximum extent possible; any imported material will be removed from the streambed upon completion of the project. BIO/mm-30 Unless approved by the United States Fish and Wildlife Service, water will not be impounded in a manner that may attract California red-legged frogs. BIO/mm-31 A United States Fish and Wildlife Service-approved biologist will permanently remove any individuals of exotic species, such as bullfrogs, crayfish, and centrarchid fishes from the project area, to the maximum extent practicable. The United States Fish and Wildlife Service- approved biologist will be responsible for ensuring their activities are in compliance with the California Fish and Game Code. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 37 of 100 BIO/mm-32 If the City of Arroyo Grande Public Works Department demonstrates that disturbed areas have been restored to conditions that allow them to function as habitat for the California red-legged frog, these areas will not be included in the amount of total habitat permanently disturbed. BIO/mm-33 To ensure that diseases are not conveyed between work sites by the United States Fish and Wildlife Service-approved biologist, the fieldwork code of practice developed by the Declining Amphibian Task Force will be followed at all times. BIO/mm-34 Project sites will be re-vegetated with an assemblage of native riparian, wetland, and upland vegetation suitable for the area. Locally collected plant materials will be used to the extent practicable. Invasive, exotic plants will be controlled to the maximum extent practicable. This measure will be implemented in all areas disturbed by activities within the project area, unless the United States Fish and Wildlife Service, California Department of Transportation, and City of Arroyo Grande Public Works Department have determined that it is not feasible or practical. BIO/mm-35 The City of Arroyo Grande Public Works Department will not use herbicides as the primary method to control invasive, exotic plants. However, if the City of Arroyo Grande Public Works Department determines the use of herbicides is the only feasible method for controlling invasive plants at a specific project site, it will implement the following additional measures to protect California red-legged frog: a. The City of Arroyo Grande Public Works Department will not use herbicides during the breeding season for California red-legged frog. b. The City of Arroyo Grande Public Works Department will conduct surveys for California red-legged frog immediately prior to the start of herbicide use. If found, California red- legged frog will be relocated to suitable habitat far enough from the project area that no direct contact with herbicide would occur. c. Giant reed and other invasive plants will be cut and hauled out by hand and painted with glyphosate-based products, such as Aquamaster® or Rodeo®. d. Licensed and experienced City of Arroyo Grande staff or a licensed and experienced contractor will use a hand-held sprayer for foliar application of Aquamaster® or Rodeo® where large monoculture stands occur at an individual project site. e. All precautions will be taken to ensure that no herbicide is applied to native vegetation. f. Foliar applications of herbicide will not occur when wind speeds are in excess of 3 miles per hour. g. No herbicides will be applied within 24 hours of forecasted rain. h. Application of herbicides will be done by a qualified City of Arroyo Grande staff or contractors to ensure that overspray is minimized, that application is made in accordance with the label recommendations, and that required and reasonable safety measures are implemented. A safe dye will be added to the mixture to visually denote treated sites. Application of herbicides will be consistent with the United States INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 38 of 100 Environmental Protection Agency’s Office of Pesticide Programs Endangered Species Protection Program county bulletins. i. All herbicides, fuels, lubricants, and equipment will be stored, poured, or refilled at least 60 feet from riparian habitat or water bodies in a location where a spill would not drain directly toward aquatic habitat. The City of Arroyo Grande Public Works Department will ensure that a plan is in place for a prompt and effective response to accidental spills. All workers will be informed of the importance of preventing spills and of the appropriate measures to take should a spill occur. Western Pond Turtle BIO/mm-36 Prior to construction, a biologist determined qualified by the California Department of Transportation and California Department of Fish and Wildlife shall survey the project site and, if present, capture and relocate any western pond turtles to suitable habitat upstream of the project site. Observations of these or other special-status species shall be documented on California Natural Diversity Database forms and submitted to the California Department of Fish and Wildlife upon project completion. If western pond turtle or other special concern aquatic species are observed during construction, they will likewise be relocated to suitable upstream habitat by a qualified biologist. Least Bell’s Vireo, Southwestern Willow Flycatcher, and Other Nesting Migratory Birds BIO/mm-37 Prior to construction, when feasible, tree removal will be scheduled to occur outside of the typical nesting bird season (February 15 through September 1), to avoid potential impacts to nesting birds. BIO/mm-38 If construction activities are proposed during the typical nesting season (February 15 to September 1), a nesting bird survey will be conducted by qualified biologists no more than two weeks prior to the start of construction to determine presence/absence of nesting birds within 500 feet of the project site. The California Department of Transportation will be notified if federally listed nesting bird species are observed during the surveys and will facilitate coordination with the United States Fish and Wildlife Service, if necessary to determine an appropriate avoidance strategy. Likewise, coordination with California Department of Fish and Wildlife will be facilitated by the City of Arroyo Grande Public Works Department if necessary to devise a suitable avoidance plan for state-listed nesting bird species. If raptor nests are observed within 500 feet of the project area during the pre-construction nesting bird surveys, the nest(s) shall be designated an Environmental Sensitive Area and protected by a minimum 500-foot avoidance buffer until the breeding season ends or until a qualified biologist determines that all young have fledged and are no longer reliant upon the nest or parental care for survival. Similarly, if active passerine nests are observed during the pre-construction nesting bird surveys, the nest(s) shall be designated an Environmentally Sensitive Area and protected by a minimum 250-foot avoidance buffer until the breeding season ends or until a qualified biologist determines that all young have fledged and are no longer reliant upon the nest or parental care for survival. Resource agencies may consider proposed variances from these buffers if there is a compelling biological or ecological reason to do so, such as protection of a nest via concealment due to site topography. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 39 of 100 Townsend’s Big-Eared Bat and Other Roosting Bats BIO/mm-39 Prior to construction, a visual survey will be conducted by a qualified biologist, at dawn and at dusk, to identify potential roosting bat activity. This survey shall be conducted between two to four weeks prior to bridge and/or tree removal activities that are proposed to occur. If roosting bat activity is identified during the preconstruction survey process, the City of Arroyo Grande will coordinate with the California Department of Fish and Wildlife regarding the biological significance of the bat population and appropriate measures that could be used to exclude bats from roosting under the bridge. Measures may include, but are not limited to the installation of exclusionary devices by a qualified individual. BIO/mm-40 If it is determined that a substantial impact to individual bat species or a maternity roost will occur, then the City of Arroyo Grande will compensate for the impact through the development and implementation of a mitigation plan in coordination with California Department of Fish and Wildlife. With the incorporation of these measures, residual impacts to biological resources would be less than significant. V. Cultural Resources Environmental Setting This section is largely based on the information provided in the Archaeological Survey Report (ASR; SWCA 2016a); Historic Property Survey Report (HPSR; JRP Historical Consulting 2017a); Historical Resource Evaluation Report (HRER; JRP Historical Consulting 2015); and the Findings of No Adverse Effect with Standard Conditions (FONAE; JRP Historical Consulting 2017b) prepared for the project. The project vicinity was inhabited by speakers of the Obispeño language of the Chumash language family. The entire project area was surveyed for archaeological resources through preparation of the ASR. No archaeological resources were identified. The Bridge Street Bridge was determined eligible for listing in the NRHP in 1985 as a result of the Caltrans Historic Bridge Inventory, which was confirmed in the Caltrans Historic Bridge Inventory update project conducted in early 2000s. The Caltrans Historic Bridge Inventory concluded the Bridge Street Bridge was eligible for listing in the NRHP under Criterion C as it embodied the distinctive characteristics of type, period, and method of construction. Built in 1908, the structure is a minor example of the American Bridge Company, a significant bridge building firm, and the bridge is an early example of a steel pin-connected pony truss. Two additional structures within the vicinity of the bridge are also designated historic properties: the Olohan Building at 101 West Branch Street (located less than 75 feet northwest of the existing bridge) and the IOOF Hall at 128 Bridge Street (located less than 75 feet southwest of the existing bridge). These properties are from the second wave of development in Arroyo Grande associated with commercial and transportation growth near the turn of the twentieth century. The IOOF Hall was listed in the NRHP in 1991. The building, constructed in 1902, is significant under Criterion C for its type, period, and method of construction as an important “embodiment of the fraternal hall format” (JRP Historical Consulting 2015). The HRER determined that the Olohan Building also meets the criteria for listing in the NRHP or California Register of Historical Resources (CRHR). INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 40 of 100 Two other buildings within the vicinity of the project site—135 Traffic Way and 127 Bridge Street—were also evaluated but were determined to not meet the criteria for listing in the NRHP or CRHR. According to geologic mapping by Hall (1973), the project site is underlain by Quaternary alluvial deposits (Holocene), which is characterized as having a low paleontological resource potential. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Cause a substantial adverse change in the significance of a historical resource as defined in § 15064.5? b) Cause a substantial adverse change in the significance of an archaeological resource pursuant to § 15064.5? c) Directly or indirectly destroy a unique paleontological resource or site or unique geologic feature? d) Disturb any human remains, including those interred outside of formal cemeteries? Discussion a) As described above, the HRER prepared for the project site identified three designated historical resources within the project area including the existing Bridge Street Bridge. An FONAE has been prepared for the project, which includes Secretary of the Interior’s (SOI) Standards to be implemented that would reduce impacts to the bridge to less than significant. According to the FONAE, the bridge rehabilitation is designed to retain the bridge’s integrity of location, design, materials, workmanship, setting, feeling, and association. The bridge would retain integrity of location because, even though it will be temporarily removed from its site, the structure will be reinstalled in its original location. The rehabilitation would be conducted in accordance with SOI Standards for Rehabilitation and would retain the original bridge design as a pony through truss. Rehabilitation would also retain the character defining materials, namely the steel truss, and the workmanship used to produce and assemble the bridge. The most significant design modification is the proposed widening of the bridge structure by 3 feet. Materials to be replaced are common materials to bridge construction at the time of original construction and will be replaced with similar materials. Through implementation of SOI Standards for Rehabilitation to preserve the bridge’s original design features, the bridge would retain the integrity of feeling and association as a small-scale truss bridge along Arroyo Grande Creek within the Arroyo Grande commercial district. These alterations were found to be consistent with the SOI Standards for the Treatment of Historic Properties. The proposed project would not result in a change in use, alteration, physical change, repair, or replacement of the two designated historical properties within the vicinity of the project site— the Olohan Building and the IOOF Hall. Both buildings would retain all historic elements and remain in their current condition. The buildings would retain their location, design, and workmanship. Furthermore, the rehabilitation of the bridge would not introduce new visual or atmospheric effects that will alter the INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 41 of 100 setting, feeling, or association for either building as the bridge will remain a small two-lane facility retaining its scale and height. The FONAE determined that the application of SOI Standards and other relevant construction measures would ensure that the project would not generate visual, atmospheric, or audible elements that would diminish the historic integrity of either historic property. The FONAE prepared for the project concluded that the proposed rehabilitation project would avoid adverse effects to historic structures by designing, dissembling, and rebuilding the bridge in a manner consistent with the SOI Standards for Rehabilitation. In addition, State CEQA Guidelines §15126.4(b), Mitigation Measures Related to Impacts on Historical Resources, states the following: 1) Where maintenance, repair, stabilization, rehabilitation, restoration, preservation, conservation or reconstruction of the historical resource will be conducted in a manner consistent with the Secretary of the Interior's Standards for the Treatment of Historic Properties with Guidelines for Preserving, Rehabilitating, Restoring, and Reconstructing Historic Buildings (1995), Weeks and Grimmer, the project's impact on the historical resource shall generally be considered mitigated below a level of significance and thus is not significant. Therefore, potential impacts related to historic resources would be less than significant. b) The ASR prepared for the project area determined that six previously documented archaeological sites are located within a 0.5-mile radius. Site types include a prehistoric lithic scatter, a prehistoric campsite, a prehistoric habitation site with bedrock mortars, and a multi-component prehistoric and historic debris scatter (CA-SLO-2643/H). CA-SLO-2643/H is the closest of the six previously documented archaeological resources within 0.5 mile of the archaeological Area of Potential Effects (APE). Previous excavations revealed that the CA-SLO-2643/H site is highly disturbed, lacked depositional integrity, and did not qualify as a historical resource as defined by CEQA. The CA-SLO- 2643/H does not extend into the project area and no further consideration of the site is warranted. The remaining five archaeological resources are located more than 0.25 mile from the project area. Portions of the project would require excavation in areas of native soil or at depths in subsurface areas containing native soils. The ASR concluded that the likelihood of native soils containing intact archaeological resources in the project area is low and, given the amount of previous disturbance within the APE, the low geo-archaeological sensitivity, and a lack of identified archaeological resources, the project area is considered to have low sensitivity for the presence of buried and/or obscured resources. Standard mitigation has been proposed to ensure impacts to any unknown resources that may be encountered during project development would be minimized. Therefore, potential impacts associated with archaeological resources would be less than significant with mitigation c) The combined results of the literature review and museum records search indicate that the project area is underlain by geologic units determined to have low paleontological resource potential. Subsurface disturbance associated with project implementation is also minimal. Therefore, impacts would be less than significant. d) No human remains are known to exist within the project area outside of formally delineated cemeteries, and the likelihood for unknown remains to exist is very low due to the extent of previous disturbance at the site. In addition, based on the archaeological survey, there is no evidence indicating INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 42 of 100 presence of burial sites within the affected area. However, the discovery of unknown human remains is always a possibility during ground disturbances. Protocol for properly responding to the inadvertent discovery of human remains is identified in the State of California Health and Safety Code §7050.5. This code section states that no further disturbance shall occur until the County Coroner has made a determination of origin and disposition pursuant to Public Resources Code §5097.98. The County Coroner must be notified of the find immediately. If the human remains are determined to be prehistoric, the County Coroner will notify the California Native American Heritage Commission (NAHC), which will determine and notify a most likely descendant. The potential for discovery of unknown buried human remains at the site is low, and compliance with existing state law requirements would minimize adverse impacts. Therefore, potential impacts associated with the disturbance of human remains would be less than significant. Mitigation Measures and Residual Impact To minimize the potential significant impacts to cultural resources, the following mitigation measures would be implemented. CUL/mm-1 If a potentially significant cultural resource is encountered during subsurface earthwork activities, all construction activities within a 100-foot radius of the find shall cease until a qualified archaeologist determines whether the uncovered resource requires further study. A standard inadvertent discovery clause shall be included in every grading and construction contract to inform contractors of this requirement. Any previously undiscovered resources found during construction shall be recorded on appropriate California Department of Parks and Recreation forms and evaluated for significance in terms of California Environmental Quality Act criteria by a qualified archaeologist. Potentially significant cultural resources consist of, but are not limited to, stone, bone, glass, ceramic, wood, or shell artifacts; fossils; or features including hearths, structural remains, or historic dumpsites. If the resource is determined significant under the California Environmental Quality Act, the qualified archaeologist shall prepare and implement a research design and archaeological data recovery plan that will capture those categories of data for which the site is significant. The archaeologist shall also perform appropriate technical analysis, prepare a comprehensive report, and file it with the appropriate Information Center and provide for the permanent curation of the recovered materials. With the incorporation of these measures, residual impacts to cultural resources would be less than significant. VI. Geology and Soils Environmental Setting The proposed project is located within the Coast Ranges province, which is characterized by its many elongate mountain ranges and valleys, extending 600 miles along the coast of California from the Oregon border south to the Santa Ynez River in Santa Barbara County. The Arroyo Grande Valley (and the southern Cienega Valley portion) is located near the intersection of the California coastal ranges and the Los Angeles ranges. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 43 of 100 The project site encompasses an urban area that is generally flat within the city of Arroyo Grande at elevations ranging from 75 to 100 feet above mean sea level. Arroyo Grande is located in a geologically complex and seismically active region. Seismic, or earthquake- related, hazards have the potential to result in significant public safety risks and widespread property damage. Two of the direct effects of an earthquake include the rupture of the ground surface along the trend or location of a fault, and ground shaking that results from fault movement. Other geologic hazards that may occur in response to an earthquake include liquefaction, seismic settlement, and landslide. The main trace of the Wilmar Avenue Fault is the closest fault to the project site. According to the City’s General Plan, the Wilmar Avenue Fault is a potentially active fault adjacent to the city of Arroyo Grande. The Wilmar Avenue Fault is exposed in a sea cliff in Pismo Beach, and the buried trace of the fault is inferred to strike northwest-southeast parallel and adjacent to US 101 beneath portions of Arroyo Grande. This potentially active fault poses a moderate potential fault rupture hazard to the city. The main trace of the Wilmar Avenue Fault is located approximately 500 feet west of the project site at the nearest point (Earth Systems Pacific 2004). The Los Osos Fault is located approximately 3 miles northeast of the project site. There are no known faults that cross or are located immediately in the project site (Earth Systems Pacific 2004). Soils within the project area are Still gravelly sandy clay loam (2 to 9 percent slopes), Riverwash, and Mocho silty clay loam (0 to 2 percent slopes, MRLA 14) (NRCS 2016). The NRCS Web Soil Survey was used to estimate the erodibility of the project site. The erosion factor within the project area was in the lower third of the range for erodibility. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Expose people or structures to potential substantial adverse effects, including the risk of loss, injury, or death involving: i) Rupture of a known earthquake fault, as delineated on the most recent Alquist-Priolo Earthquake Fault Zoning Map, issued by the State Geologist for the area, or based on other substantial evidence of a known fault? (Refer to Division of Mines and Geology Special Publication 42.) ii) Strong seismic ground shaking? iii) Seismic-related ground failure, including liquefaction? iv) Landslides? b) Result in substantial soil erosion or the loss of topsoil? INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 44 of 100 Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact c) Be located on a geologic unit or soil that is unstable, or that would become unstable, as a result of the project and potentially result in on- or off-site landslide, lateral spreading, subsidence, liquefaction, or collapse? d) Be located on expansive soil, as defined in Table 18- 1-B of the Uniform Building Code (1994), creating substantial risks to life or property? e) Have soils incapable of adequately supporting the use of septic tanks or alternative waste disposal systems, where sewers are not available for the disposal of waste water? Discussion a) – d) The project is located in an area with multiple geological characteristics that could contribute to unstable earth/soil conditions, including compressible/collapsible soils, high groundwater elevation, moderate liquefaction potential, and moderately high potential for seismic activity, ground shaking, and seismic settlement. The placement of structures within these soil conditions creates the risk for structure instability, damage, failure, and/or collapse. Development of the project would be required to meet or exceed the most current requirements of AASHTO, which have been developed to establish the minimum requirements necessary for design to safeguard the public health, safety, and general welfare through structural strength, stability, access, and other standards. Compliance with AASHTO, Caltrans, and other applicable standards would typically indicate that people and structures were properly safeguarded against risks, including those related to unstable soil conditions. The project does not propose development of any habitable structures; therefore, no risk of injury or death as a result of damage or collapse of a habitable structure would occur. The project would improve public safety and the stability of the bridge; through compliance with applicable standards, the structural components of the project would be designed to withstand anticipated seismic and geologic stresses according to current established engineering practices. Therefore, impacts would be less than significant. e) The project does not propose installation of any septic disposal system. Therefore, no impacts would occur. Mitigation Measures and Residual Impacts No significant impacts related to geology or soils were identified; therefore, no mitigation measures are necessary. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 45 of 100 VII. Greenhouse Gas Emissions Environmental Setting GHGs are any gases that absorb infrared radiation in the atmosphere, and are different from the criteria pollutants discussed in Section III, Air Quality, above. The primary GHGs that are emitted into the atmosphere as a result of human activities are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases. These are most commonly emitted through the burning of fossil fuels (i.e., oil, natural gas, and coal), agricultural practices, decay of organic waste in landfills, and a variety of other chemical reactions and industrial processes (e.g., the manufacturing of cement). CO2 is the most abundant GHG and is estimated to represent approximately 80–90% of the principal GHGs that are currently affecting the earth’s climate. According to the CARB, transportation (vehicle exhaust) and electricity generation are the main sources of GHG in the state. The passage of Assembly Bill (AB) 32, the California Global Warming Solutions Act, in 2006 recognized the need to reduce GHG emissions and set the GHG emissions reduction goal for the State of California into law. The law required that by 2020, state emissions must be reduced to 1990 levels. This is to be accomplished by reducing GHG emissions from significant sources via regulation, market mechanisms, and other actions. Subsequent legislation (e.g., Senate Bill [SB] 97, Greenhouse Gas Emissions bill) directed the CARB to develop statewide thresholds. In March 2012, the APCD approved thresholds for GHG emission impacts, and these thresholds have been incorporated into the APCD’s CEQA Air Quality Handbook. APCD determined that a tiered process for land use development projects was the most appropriate and effective approach for assessing the GHG emission impacts. The tiered approach includes three methods, any of which can be used for any given project: 1. Qualitative GHG Reduction Strategies (e.g., Climate Action Plans): A qualitative threshold that is consistent with AB 32 Scoping Plan measures and goals; or, 2. Bright-Line Threshold: A numerical value to determine the significance of a project’s annual GHG emissions; or, 3. Efficiency-Based Threshold: Assesses the GHG impacts of a project on an emissions per capita basis. The City of Arroyo Grande adopted a Climate Action Plan (CAP) on November 26, 2013. The City’s CAP is a long-range plan to reduce GHG emissions from City government operations and community activities within Arroyo Grande and prepare for the anticipated effects of climate change. To achieve the state- recommended target of 15% below 2005 levels (71,739 metric tons of CO2 equivalent [MT CO2e]) by 2020 and prepare for the anticipated effects of climate change, the CAP identifies climate action measures. Collectively, the measures identified in the CAP have the potential to reduce GHG emissions within Arroyo Grande by 5,371 MT CO2e (17% below the 2005 baseline) by 2020 and meet the reduction target. For most projects, the Bright-Line Threshold of 1,150 MT CO2e per year (MT CO2e/yr) will be the most applicable threshold. In addition to the land use development threshold options proposed above, a bright-line numerical value threshold of 10,000 MT CO2e/yr was adopted for stationary source (industrial) projects. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 46 of 100 It should be noted that projects that generate less than the above-mentioned thresholds will also participate in emission reductions because air emissions, including GHGs, are under the purview of the CARB (or other regulatory agencies) and will be “regulated” by either CARB, the federal government, or other entities. For example, new vehicles will be subject to increased fuel economy standards and emission reductions, large and small appliances will be subject to more strict emissions standards, and energy delivered to consumers will increasingly come from renewable sources. Other programs that are intended to reduce the overall GHG emissions include Low Carbon Fuel Standards, Renewable Portfolio standards, and the Clean Car standards. As a result, even the emissions that result from projects that produce fewer emissions than the threshold will be subject to emission reductions. Under CEQA, an individual project’s GHG emissions will generally not result in direct significant impacts. This is because the climate change issue is global in nature. However, an individual project could be found to contribute to a potentially significant cumulative impact. Projects that have GHG emissions above the noted thresholds may be considered cumulatively considerable and require mitigation. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Generate greenhouse gas emissions, either directly or indirectly, that may have a significant effect on the environment? b) Conflict with an applicable plan, policy or regulation adopted for the purpose of reducing the emissions of greenhouse gases? Discussion a), b) This project includes the rehabilitation of an existing bridge and would not create a new use in the area. No GHG emissions above existing levels would be generated by the project except during short-term construction activities. The project would not exceed any applicable GHG threshold; therefore, the project’s potential direct and cumulative GHG emissions constitute a less-than-significant impact and a less-than-cumulatively-considerable contribution to global GHG emissions. State CEQA Guidelines §15064(h)(2) provides guidance on how to evaluate cumulative impacts. If it is shown that an incremental contribution to a cumulative impact, such as global climate change, is not “cumulatively considerable,” no mitigation is required. Because this project’s emissions are not cumulatively considerable, no mitigation for GHG emissions is required. Impacts would be less than significant. Mitigation Measures and Residual Impacts No significant impacts related to GHGs were identified; therefore, no mitigation measures are necessary. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 47 of 100 VIII. Hazards and Hazardous Materials Environmental Setting The information in this section relies on the Phase I Initial Site Assessment (ISA) prepared for the proposed project (Fugro Consultants 2013). No clean-up sites are identified within the project area in the State Water Resources Control Board’s (SWRCB) GeoTracker database, California Department of Toxic Substances Control EnviroStor database, or California Environmental Protection Agency’s (Cal/EPA) Cortese List (which is a list of hazardous materials sites compiled pursuant to Government Code §65962.5). The project site does not contain hazardous waste and there is no evidence of Underground Storage Tanks (UST), pits, sumps, clarifiers, or other potential hazardous material conditions that might impact the underlying soil or groundwater. The project site did not reveal any indications of stained soil, or stressed vegetation. Minor oil staining was observed on the pavement, but is considered to be a de minimis condition. The existing bridge is generally composed of steel beams, trusses, wood planks, concrete, and asphalt pavement. Other materials on the site include paint and tar coating. Below the bridge, the creek embankments are relatively steep and heavily vegetated with blackberry bushes and vines. The project site supports local vehicular use. It is highly likely that the surface soils along these roadways are affected by deposition of contaminants, including aerial lead, oils, fuels, and other lubricants. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Create a significant hazard to the public or the environment through the routine transport, use, or disposal of hazardous materials? b) Create a significant hazard to the public or the environment through reasonably foreseeable upset and/or accident conditions involving the release of hazardous materials, substances, or waste into the environment? c) Emit hazardous emissions or handle hazardous or acutely hazardous materials, substances, or waste within one-quarter mile of an existing or proposed school? d) Be located on a site which is included on a list of hazardous materials sites, compiled pursuant to Government Code §65962.5, and, as a result, create a significant hazard to the public or environment? INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 48 of 100 Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact e) Be located within an airport land use plan or, where such a plan has not been adopted, within two miles of a public airport or public use airport? If so, would the project result in a safety hazard for people residing or working in the project area? f) Be located in the vicinity of a private airstrip? If so, would the project result in a safety hazard for people residing or working in the project area? g) Impair implementation of or physically interfere with an adopted emergency response plan or emergency evacuation plan? h) Expose people or structures to a significant risk of loss, injury, or death from wildland fires, including areas where wildlands are adjacent to urbanized areas or where residences are intermixed with wildlands? Discussion a), c) The proposed project would not change existing land uses or cause a routine or permanent increase in the transport of hazardous substances within the project area. The closest school to the project site is Village Preschool, located less than 0.1 mile southwest of the project site on Traffic Way. The project would not require the use or handling of acutely hazardous materials and would not change the long-term transport or handling of hazardous materials within proximity to adjacent schools. Therefore, impacts would be less than significant. b) Oils, gasoline, lubricants, fuels, and other potentially hazardous substances would be used and stored on-site during construction activities. Should a spill or leak of these materials occur during construction activities, sensitive resources within the project vicinity could be adversely affected. Such activities would also occur in close proximity to Kiwanis Park and other sensitive adjacent land uses. However, such use would be short term and subject to standard requirements for the handling of hazardous materials. Standard mitigation would be implemented to ensure potential impacts were reduced to less than significant. The project does not propose the use, storage, or discharge of any hazardous substances during project operation and would not change the existing land use of the project site or substantially increase the potential use of hazardous materials in the project vicinity. Therefore, the project would not create a significant long-term hazard to the public through foreseeable accident or upset. Existing infrastructure proposed to be demolished could include asbestos-containing materials (ACM), lead-based paint, or aerially-deposited lead. Arsenic was detected in the wooden bridge members. The Phase I ISA prepared by Fugro Consultants detected no asbestos in the existing paint on the bridge and railings, no asbestos in the asphalt bridge deck, and no asbestos in the concrete sidewalk leading to the bridge or the pipe wrap below the bridge. No naturally occurring asbestos was detected in soil samples INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 49 of 100 collected near the approaches to the bridge. The ISA confirmed that the green paint on the steel bridge contained a lead concentration of 72,000 mg/kg and the yellow lane-dividing paint stripping on the bridge deck contained 6,600 mg/kg of lead. Fugro observed an elevated arsenic concentration in a sample of the wooden walkway and support beams of the bridge. No polychlorinated biphenyls (PCBs) were detected in the pipe wrap below the bridge. Total lead concentrations detected in surface soil samples collected at the approaches to the bridge were less than the California Human Health Screening Level of 80 milligrams/kilogram. Disturbance and handling of these toxic substances can result in significant health impacts on workers or other persons exposed to the substances. They can also damage adjacent habitats and contaminate proximate soils, surfaces, and waters that receive stormwater runoff from within the project area. Implementation of BMPs, included as mitigation measures below, would therefore be employed during demolition and construction activities to reduce potential impacts to less-than-significant levels. Therefore, potential impacts would be less than significant with mitigation. d) There are no active hazardous material sites within the project boundary. No disturbance is proposed within 0.5 mile of a UST clean-up site. Therefore, potential impacts related to active hazardous material sites would be less than significant. e), f) The project site is not located within an airport land use plan or within 2 miles of any public airport or private airstrip. The proposed project would not substantially change existing uses and would not result in increased hazards related to air traffic. Therefore, impacts would be less than significant. g) The project would improve existing transportation infrastructure to improve safety. The project would improve long-term access and circulation in the project vicinity and adequate alternative access exists for emergency purposes during construction activities. The project would not interfere with any emergency response or evacuation plans. Therefore, impacts would be less than significant. h) The proposed project is located in an urban area and would not expose people or structures to a substantial risk of wildfires. The Five Cities Fire Authority Arroyo Grande Station is located less than 0.5 mile from the project site and response times would be within acceptable levels. Therefore, impacts would be less than significant. Mitigation Measures and Residual Impact To minimize the potential significant impacts related to hazards and hazardous materials, the following mitigation measures would be implemented. HAZ/mm-1 Prior to construction, the City of Arroyo Grande Public Works Department shall prepare a Hazardous Material Spill Prevention, Control and Countermeasure Plan to minimize the potential for, and effects of, spills of hazardous or toxic substances during construction of the project. The plan shall be submitted for review and approval by the City of Arroyo Grande Public Works Director, and shall include, at minimum, the following: INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 50 of 100 a. A description of storage procedures and construction site maintenance and upkeep practices; b. Identification of a person or persons responsible for monitoring implementation of the plan and spill response; c. Identification of Best Management Practices to be implemented to ensure minimal impacts to the environment occur, including but not limited to the use of containment devices for hazardous materials, training of construction staff regarding safety practices to reduce the chance for spills or accidents, and use of non-toxic substances where feasible; d. A description of proper procedures for containing, diverting, isolating, and cleaning up spills, hazardous substances and/or soils, in a manner that minimizes impacts on surface and groundwater quality and sensitive biological resources; e. A description of the actions required if a spill occurs, including which authorities to contact and proper clean-up procedures; and f. A requirement that all construction personnel participate in an awareness training program conducted by qualified personnel approved by the City of Arroyo Grande Public Works Director. The training must include a description of the Hazardous Materials Spill Prevention, Control and Countermeasure Plan, the plan’s requirements for spill prevention, information regarding the importance of preventing spills, the appropriate measures to take should a spill occur, and identification of the location of all clean-up materials and equipment. HAZ/mm-2 A Soil Management Plan and Health and Safety Plan shall be developed for the project and subject to approval by the City of Arroyo Grande Public Works Department to ensure contaminated soils excavated during the project construction are handled, stockpiled, and disposed of in accordance with federal, state, and local regulations. Soils excavated during the project shall be tested for lead concentrations and the Soil Management Plan shall establish a Reuse Screening Level for the excavated soils; excavated soils with contaminant concentrations below the Reuse Screening Levels may be reused during construction on the right-of-way, while soils with contaminant concentrations exceeding the Reuse Screening Levels shall be managed as hazardous waste and disposed of at a facility that accepts soil with the detected concentrations of contaminants. Special handling, treatment, or disposal of aerially deposited lead in soils during construction activities shall be consistent with the California Department of Toxic Substances Control Lead Variance (No. V09HQSCD006) dated July 1, 2009. HAZ/mm-3 Prior to initiation of construction, a Lead Compliance Plan shall be prepared by the contractor to prevent or minimize worker exposure to lead from handling material containing lead based paint or aerially-deposited lead (California Code of Regulations, Title 8, Section 1532.1). This plan shall also be required for work performed on painted structures. The contractor shall prepare a written, project-specific Excavation and Transportation Plan establishing procedures the contractor shall use for excavating, stockpiling, transporting, and placing (or disposing) of material containing lead-based paint or aerially-deposited lead. The plan must conform to Department of Toxic Substance Control and California Occupational Safety and Health Administration regulations. For samples where lead levels exceed hazardous waste INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 51 of 100 criteria, the excavated soil shall be either managed or disposed of as a California hazardous waste or stockpiled and resampled to confirm waste classification and potential utilization of Caltrans’ hazardous waste variance agreement to recycle soil on site. The appropriate Caltrans Standard Special Provision shall be included in the Plans, Specifications, and Estimate. HAZ/mm-4 Conventional demolition techniques for painted surfaces and treated wood members shall comply with Occupational Safety and Health Administration and California Occupational Safety and Health Administration statutes regarding worker awareness training, exposure monitoring, and medical examinations, and should include a written respiratory protection program. Dust control procedures shall be implemented in compliance with California Code of Regulations, Title 8, Section 1532.1, during abatement, demolition, and/or renovation of the bridge. Pulverization and/or activities that may result in the generation of fine dust and particulates shall be prohibited at the project site. HAZ/mm-5 Materials that are excavated or water that accumulates within an excavation during construction activities should not be discarded to the ground surface, watershed, or waterway. Accumulated or excavated materials should be segregated, placed on and covered by plastic sheeting, and characterized to aid in evaluating and documenting contractor-proposed handling, re-use, or disposal. Contractor proposed handling, re-use, or disposal of waste materials should be conducted in accordance with local material management jurisdictions and/or receiving facility criteria. With the incorporation of these measures, residual impacts related to hazards and hazardous materials would be less than significant. IX. Hydrology and Water Quality Environmental Setting This following information is based on information provided in the Water Quality Assessment Memorandum prepared for the project (SWCA 2016c). The project site is located within the Arroyo Grande Creek watershed, a coastal basin with headwaters that originate at approximately 3,100 feet above mean sea level and eventually drain to the Pacific Ocean. Arroyo Grande Creek drains the 157-square-mile watershed and is the dominant surface water feature in the city. Flows in the creek are dominated by two factors: winter rains and Lopez Dam. Arroyo Grande Creek is included on the Section 303(d) list of impaired waterbodies for elevated concentrations of fecal coliform and Escherichia coli (E. coli). Arroyo Grande Creek has been altered since the late 1950s for flood control, water supply, and groundwater recharge purposes. The most substantial alterations include the construction of a flood control channel and Lopez Dam. The Dam collects and provides water to municipalities and releases for downstream users, while the flood control channel provides flood protection to the productive farmlands of the Cienega Valley. Sediment buildup, increased runoff resulting from upstream development, and settling of the earthen levees have reduced the flood protection benefits of the channel over time, and larger storms (approximately 4.6-year storms or larger) result in localized flooding approximately once every 5 years. In 2010, the County of San Luis Obispo developed the Arroyo Grande Creek Waterway Management Program to restore capacity within the channel to provide flood protection from up to a 20-year storm event while simultaneously enhancing water quality and sensitive species habitat. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 52 of 100 Within the project site, Arroyo Grande Creek runs through a deep channel with steep sides and dense vegetation. The natural depth of the channel provides capacity for significant flood protection and within the project area, only areas within the waterway or directly adjacent to it are within the Federal Emergency Management Agency (FEMA) 100-year flood zone. The FEMA 100-year flood zone identifies areas that would be subject to inundation in a 100-year storm event, or a storm with a 1% chance of occurring in a year. While flood protection at the project site is generally adequate, the project area and surrounding vicinity are heavily urbanized, which leads to increased stormwater runoff, erosion of creek banks, and sedimentation of the creek, as well as heightened potential for substantially greater damage and injury in a flood event. Floodways are defined as stream channels plus adjacent floodplains that must be kept free from encroachments to the greatest extent feasible so that 100-year floods can be carried without substantial increases in flood elevations. According to FEMA flood maps (Map Number: 06079C1602G; Map Revised November 16, 2012), the project site is located within a special flood hazard area subject to inundation by the 1% annual chance flood (100-year flood) of the Arroyo Grande Creek (FEMA 2012). The project site is located within special flood hazard areas designated as Zone AE (Floodway Area), the channel of a stream plus adjacent areas that must be kept free of encroachment so that the 1% annual chance flood can be carried without substantial increases in flood heights. The project site is located within the northern portion of the Santa Maria River Valley Groundwater Basin, in the Arroyo Grande Creek Unit. The Santa Maria River Valley Groundwater Basin encompasses approximately 288 square miles within the coastal northern portion of Santa Barbara County and the southern portion of San Luis Obispo County. In San Luis Obispo County, the Santa Maria Basin consists of the main basin (Santa Maria) and three subbasins: Arroyo Grande Valley, Pismo Creek Valley, and Nipomo Valley. The project site is within the Arroyo Grande Valley subbasin, which is drained by Arroyo Grande Creek and its tributaries from below Lopez Lake Dam to the basin’s southern boundary at the Wilmar Avenue Fault. Groundwater flow is generally westward toward the Pacific Ocean. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Violate any water quality standards or waste discharge requirements? b) Substantially deplete groundwater supplies or interfere substantially with groundwater recharge, such that there would be a net deficit in aquifer volume or a lowering of the local groundwater table level (e.g., the production rate of pre-existing nearby wells would drop to a level that would not support existing land uses or planned uses for which permits have been granted)? c) Substantially alter the existing drainage pattern of the site or area, including through alteration of the course of a stream or river, in a manner which would result in substantial on- or off-site erosion or siltation? INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 53 of 100 Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact d) Substantially alter the existing drainage pattern of the site or area, including through alteration of the course of a stream or river, or substantially increase the rate or amount of surface runoff in a manner which would result in on- or off-site flooding? e) Create or contribute runoff water which would exceed the capacity of existing or planned stormwater drainage systems or provide substantial additional sources of polluted runoff? f) Substantially degrade water quality? g) Place housing within a 100-year flood hazard area, as mapped on a federal Flood Hazard Boundary or Flood Insurance Rate Map, or other flood hazard delineation map? h) Place structures that would impede or redirect flood flows within a 100-year flood hazard area? i) Expose people or structures to a significant risk of loss, injury, or death from flooding, including flooding resulting from the failure of a levee or dam? j) Result in inundation by seiche, tsunami, or mudflow? Discussion a), f) Potential adverse effects of the project related to water quality are limited to construction- related impacts such as erosion, sedimentation, and the potential release of hazardous construction- related materials. Grading activities could result in sedimentation of the Arroyo Grande Creek if water is present. Arroyo Grande Creek flows are intermittent and can run dry during the summer; however, it is possible for water to be present within the channel due to releases by the Lopez Dam. Therefore, proposed construction activities associated with the rehabilitation of the Bridge Street Bridge, located directly above the Arroyo Grande Creek channel, could have the potential to result in direct impacts to water quality and hydrology whether construction activities take place during the wet season or the dry season. The proposed project could introduce sediment and potential sources of pollution in the form of improper use of fuels, oils, and other construction-related hazardous waste materials, which could pose a threat to surface and/or groundwater quality. Implementation of erosion control standards and hazardous materials spill pollution and prevention standards would be required to ensure the proposed project does not impact the water quality of the Arroyo Grande Creek or groundwater resources. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 54 of 100 For general construction activities, the proposed project would be required to comply with a National Pollutant Discharge Elimination System (NPDES) General Construction Permit to discharge stormwater associated with construction activities. Additionally, the project would be required to prepare a stormwater pollution prevention plan (SWPPP) that addresses the quality and quantity of stormwater runoff generated on-site during construction and operation of the project, and incorporate temporary BMPs. Implementation of temporary BMPs would minimize impacts to water quality that could occur as a result of construction of the proposed project. Long-term impacts to water quality resulting from pollutants in the form of gasoline or oil residue from vehicle traffic collecting on the bridge and draining to the Arroyo Grande Creek would not change substantially over existing conditions. New stormwater infrastructure would be constructed to reroute surface runoff off the bridge to roadway drainage systems, reducing potential impacts to water quality in the creek below. Therefore, impacts related to water quality would be less than significant with mitigation. b) Construction activities associated with the proposed project that require ground disturbance within the channel could disturb the groundwater table, rendering groundwater exposed to potential contamination. Implementation of temporary BMPs would minimize potential impacts of the project from contributing to the impairment of groundwater. The project does not involve the construction or use of a well or sewage disposal and would not result in a threat of aquifer contamination or a hazard to public health. The project would not create long-term water demand and would not deplete groundwater supplies. Short-term construction-related water demands would be served by the City’s non-potable municipal water supply. Therefore, impacts related to groundwater would be less than significant. c) – e) The existing bridge allows roadway drainage to sheet flow directly into Arroyo Grande Creek. Current environmental permit requirements usually stipulate that the stormwater on bridges be collected and transported off the bridge into a roadway drainage facility. The proposed project would be crowned at the roadway centerline and would utilize concrete curbs and a longitudinal slope in order to collect the stormwater. Eventually, the roadway drainage system will empty into the creek. The proposed modifications (particularly the widened bridge deck) would increase impervious surfaces at the project site by less than 15,000 square feet, which would increase the volume and rate of stormwater flows and increase the risk of erosion, sedimentation, scour, and pollutant discharge. The project will comply with all applicable requirements outlined in the City’s Storm Water Management Program and will satisfy Performance Requirements (PR) PR1 (Site Design and Runoff Reduction) and PR2 (Water Quality Treatment) of the Central Coast RWQCB’s Post-Construction Storm Water Management Requirements (Resolution R3-20132-0032025). The City proposes to meet PR1 and PR2 requirements on-site to ensure reduction of pollutant discharges to the maximum extent practicable and prevent stormwater discharges from causing or contributing to a violation of receiving water quality standards. It is possible that the project would require access into the creek to install the temporary falsework and other activities. Access may be achieved by temporarily diverting water through or around the work area and constructing a temporary access route into the creek channel. Water diversion may be accomplished with a combination of cofferdams, pipes, sand bags, and temporary fill. If a temporary culvert or diversion dam is placed in the creek, it will be sized and placed appropriately to allow fish INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 55 of 100 passage throughout construction. The temporary access route will be located on the north bank by Kiwanis Park. The temporary access route will traverse the creek bank, enter the channel, and extend under the proposed and existing bridge. The contractor may temporarily place clean crushed rock into the creek in order to create the temporary path, construct the CIDH piles, and support the falsework. All temporary fill associated with the creek diversion and the access path will be removed after construction is complete. Abutments located within the channel will be subject to creek flows, and soils are likely to erode from around the abutments over time. Ungrouted RSP will be placed around the abutments to curtail the erosion process. Based on the current project goals and plans, RSP would be placed immediately below the bridge abutments and extend beyond the bridge rails on the northeast, northwest, and southeast banks. Therefore, impacts related to water diversion, drainage, flows, and surface runoff associated with Arroyo Grande Creek would be less than significant with mitigation. g) The proposed project would not place any housing within a 100-year flood zone. Therefore, the proposed project would result in no impact related to the placement of housing within a 100-year flood zone. h) The proposed project is located within the 100-year floodplain of the Arroyo Grande Creek; however, construction of the proposed project would not impede or redirect flood flows or reduce the capacity of the Arroyo Grande Creek or increase the boundaries of the existing 100-year floodplain. Additionally, the Bridge Street Bridge rehabilitated structure would be designed to be capable of withstanding flows from a 100-year storm. Therefore, impacts would be less than significant. i) The project would not create a new use that would expose additional people or structures to a significant risk of loss, injury, or death from flooding, including flooding resulting from the failure of a levee or dam. The rehabilitated bridge would be capable of withstanding flows from a 100-year storm. Therefore, potential impacts would be less than significant. j) The project is not in an area that would be affected by seiche, tsunami, or mudflow. No impacts would occur. Mitigation Measures and Residual Impact To minimize the potential significant impacts related to hydrology and water quality, the following mitigation measures would be implemented. Implement Mitigation Measures BIO/mm-1, 4, 6 through 11, 17, 24, and 28; and HAZ/mm-1, 2, 3, and 5. With the incorporation of these measures, residual impacts related to hydrology and water quality would be less than significant. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 56 of 100 X. Land Use and Planning Environmental Setting The project site is identified as Village Core in the City’s General Plan Land Use Map (See Figure 4) and is zoned as Village Mixed Use, Village Core Downtown, and Public Facility in the City’s Zoning Map (See Figure 5). The project site is also within the Historic Character and Conservation/Open Space (OS) land use overlays. Surrounding land uses include commercial uses associated with the downtown Village, as well as community facilities such as Kiwanis Park which extends east of the bridge along the creek; Heritage Square Park, located approximately 0.11 mile southeast of the project area; and Centennial Park, located approximately 0.9 mile east of the project area. Other land uses within the project area include local roadways and traffic/circulation infrastructure (i.e., sidewalks, right of way) as well as historic buildings associated with the historic village district (refer to Section V. Cultural Resources, above). Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Physically divide an established community? b) Conflict with the applicable land use plan, policy, or regulation of any agency with jurisdiction over the project (including, but not limited to, a general plan, specific plan, local coastal program, or zoning ordinance) adopted for the purpose of avoiding or mitigating an environmental effect? c) Conflict with any applicable habitat conservation plan or natural community conservation plan? Discussion a) The project would rehabilitate an existing bridge within Arroyo Grande. The project would not divide any portion of the City. Temporary construction-related impacts would result in a short-term road closure on Bridge Street. However, alternative detours would be available via Traffic Way and Mason Street, adjacent to the bridge. Therefore, impacts would be less than significant. b) The project does not propose activities that would conflict with applicable plans and policies or agency regulations. Rehabilitation of the existing bridge would benefit public safety and bring the structure into compliance with current design and load capacity standards. The proposed project would comply with all policies within the City’s General Plan, including policies to restore historic resources and protect creek and riparian habitat. Therefore, impacts would be less than significant. c) There are no applicable HCPs or natural community conservation plans in the project vicinity. Therefore, no impacts would occur. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 57 of 100 Figure 4. Land Use Map INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 58 of 100 Figure 5. Zoning Map INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 59 of 100 Mitigation Measures and Residual Impacts No significant impacts related to land use and planning were identified; therefore, no mitigation measures are necessary. XI. Mineral Resources Environmental Setting The project site does not contain any known mineral resources. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Result in the loss of availability of a known mineral resource that is or would be of value to the region and the residents of the state? b) Result in the loss of availability of a locally important mineral resource recovery site delineated on a local general plan, specific plan, or other land use plan? Discussion a), b) There are no known mineral resources in the project area, and future extraction of mineral resources is very unlikely due to the urbanized nature of the area and proximity to the historic downtown Village. Therefore, potential impacts would be less than significant. Mitigation Measures and Residual Impact No significant impacts related to mineral resources were identified; therefore, no mitigation measures are necessary. XII. Noise Environmental Setting This section is largely based on the Noise Study Memorandum prepared for the project (SWCA 2016). The existing ambient noise environment is characterized by vehicle noise from Bridge Street and surrounding roadways as well as surrounding commercial development. Noise-sensitive receptors generally include land uses such as hospitals, schools, churches, libraries, auditoriums, public meeting rooms, motels, hotels, residences, recreational facilities, and lands on which serenity and quiet are of extraordinary importance and which serve an important public need. The Bridge Street Bridge is located within the City’s Village Core and is surrounded by various commercial developments that would be impacted by the proposed construction noise associated with the project; therefore, surrounding commercial developments are considered sensitive noise receptors. As shown in Figure 6 below and described in the Noise Study Memorandum, several noise-sensitive land uses are located adjacent to and in the vicinity of the project area. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 60 of 100 Figure 6. Sensitive Receptors INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 61 of 100 Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Generate or expose people to noise levels in excess of standards established in a local general plan or noise ordinance, or in other applicable local, state, or federal standards? b) Generate or expose people to excessive groundborne vibrations or groundborne noise levels? c) Create a substantial permanent increase in ambient noise levels in the vicinity of the project (above levels without the project)? d) Create a substantial temporary or periodic increase in ambient noise levels in the vicinity of the project, in excess of noise levels existing without the project? e) Be located within an airport land use plan or, where such a plan has not been adopted, within two miles of a public airport or public use airport? If so, would the project expose people residing or working in the project area to excessive noise levels? f) Be in the vicinity of a private airstrip? If so, would the project expose people residing or working in the project area to excessive noise levels? Discussion a), c), d) Construction-Related Noise Impacts. The nearest noise-sensitive land use is the Kiwanis Park, located immediately east of the Bridge Street Bridge. The nearest habitable noise-sensitive land use is a private residence, located approximately 400 feet east of the bridge (Assessor’s Parcel Number 007-491-062). Multiple additional downtown commercial uses are also considered sensitive due to the visitor-serving nature of the project area. Construction noise would generally be consistent with typical construction activities. No pile driving or other high impact noise sources are proposed. Construction activities would be conducted in accordance with Caltrans Standard Specifications §14-8 and applicable local noise standards. Construction noise would be short term, intermittent, and overshadowed by extant local traffic. Construction-related noise impacts are generally considered less than significant due to their limited duration. Standard mitigation measures have been identified to ensure temporary construction noise impacts would be reduced to less than significant levels. Therefore, construction-related noise impacts would be less than significant with mitigation. Operation-Related Noise Impacts. The project does not propose a new use in this area that would result in the exposure of people to any new noise sources. Therefore, operation-related noise impacts would be less than significant. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 62 of 100 b) The Federal Transit Administration (FTA) Transit Noise and Vibration Impact Assessment (FTA 2006) provides guidance for assessing vibration levels associated with construction activities. This guidance was used to assess the potential project-related vibration impacts pursuant to CEQA because the City has not established construction vibration standards. The FTA establishes a 25-foot distance reference point from residential structures to measure the severity of potential vibration impacts (measured by peak particle velocity [PPV]). Based on FTA vibration standards for general construction equipment, typical equipment (e.g., a large bulldozer) would generate a vibration level of approximately 0.089 inch per second at 25 feet, which is less than the FTA’s most stringent vibration standard for older residential structural damage of 0.5 inches per second. Since the surrounding habitable structures are all located more than 25 feet from the project limits and no significant vibration-inducing construction methods (such as pile driving) would be utilized during the replacement or rehabilitation of the bridge, significant vibration-related impacts on adjacent structures would not occur. Therefore, impacts would be less than significant. e), f) The project site is not within 2 miles of any public airport or private airstrip. The nearest airport is the Oceano County Airport, located approximately 4.3 miles southwest of the project site. Therefore, the project would result in no impact related to noise and nearby airports. Mitigation Measures and Residual Impact To minimize potential significant impacts from construction-related noise, the following measures would be implemented: NOI/mm-1 Construction activities shall be limited to the daytime hours of 7:00 a.m. to 10:00 p.m. Monday through Friday, and 8:00 a.m. to 5:00 p.m. on Saturday or Sunday, consistent with City of Arroyo Grande construction noise exception standards. NOI/mm-2 All equipment will have sound-control devices that are no less effective than those provided on the original equipment. No equipment will have an unmuffled exhaust. With the incorporation of these measures, residual impacts associated with noise would be less than significant. XIII. Population and Housing Environmental Setting Arroyo Grande’s population has grown from 3,291 in 1960 to 17,252, based on the 2010 Census. At the time of the 2010 Census, there were 7,628 housing units in the city of Arroyo Grande, an 822-unit increase from 2000. The vast majority, 75%, are single-family units. The overall average household size in Arroyo Grande is 2.41, with owner-occupied units averaging 2.45 persons per household and renter- occupied units averaging 2.33 persons per household. This rate is relatively consistent with the 1990 city average of 2.48, and slightly less than California’s average rate of 2.87 persons per household. There are no residences or residential uses within the project area; however, there are residences and commercial uses adjacent to the project site as part of the Village Core land use designation. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 63 of 100 Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Induce substantial population growth in an area, either directly (for example, by proposing new homes and businesses) or indirectly (for example, through extension of roads or other infrastructure)? b) Displace substantial numbers of existing housing, necessitating the construction of replacement housing elsewhere? c) Displace substantial numbers of people, necessitating the construction of replacement housing elsewhere? Discussion a) The proposed bridge rehabilitation project would not develop a new land use or serve as an inducement to population growth or affect the movement or concentration of population in the area. The goal of the bridge is to improve safety issues associated with existing conditions. The proposed rehabilitation project would not increase the capacity of the bridge or surrounding roadways. The proposed project would not extend roads or other infrastructure. Therefore, no impacts related to population inducement would occur. b), c) The proposed project would not displace any residences or people and would not require the construction of replacement housing elsewhere. Therefore, no impacts would occur. Mitigation Measures and Residual Impacts No significant impacts to population or housing were identified; therefore, no mitigation measures are necessary. XIV. Public Services Environmental Setting Fire Protection Services. The Five Cities Fire Authority (FCFA) was established on July 9, 2010, by a Joint Powers Agreement between the cities of Arroyo Grande, Grover Beach, and the Oceano Community Services District to provide fire protection services of these communities. FCFA also provides services to the Town of Halcyon and the Oceano Dunes State Vehicle Recreation Area. FCFA has three stations: one in Arroyo Grande, one in Grover Beach, and one in Oceano. The Arroyo Grande station (Station 1) is located at 140 Traffic Way and serves as the headquarters for FCFA and serves the city of Arroyo Grande and the greater Arroyo Grande area. The California Department of Forestry and Fire Protection (CAL FIRE) provides fire protection to surrounding communities, as well as back up support in Arroyo Grande. CAL FIRE has four substations in the area, at the following locations: 2391 Willow Road, Arroyo Grande; 450 Pioneer Road, Nipomo; 990 Bello Street, Pismo Beach; and 2555 Shell Beach Road, Pismo Beach. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 64 of 100 Police Protection Services. The City of Arroyo Grande’s police station is located at 200 North Halcyon Road. In addition to the City police station, the San Luis Obispo County Sheriff’s Office substation is located at 1681 Front Street in Oceano and provides backup support within the city of Arroyo Grande. The California Highway Patrol (CHP) office located in San Luis Obispo serves the South County, including the city of Arroyo Grande. The response times of both the Sheriff’s Office and CHP can be delayed due to the large coverage area. Emergency Medical Services. The San Luis Ambulance South County substation, located at 201 Brisco Road in Arroyo Grande, provides southern San Luis Obispo County residents with paramedic services. There are currently two units stationed at the South County substation, which provide South County residents with emergency transportation to and from the Arroyo Grande Community Hospital located at 342 South Halcyon Road. Schools. The project area is within the Lucia Mar Unified School District (LMUSD). The district serves the City of Arroyo Grande with seven public schools, including three elementary schools, two middle schools, one high school, and one adult school. The San Luis Obispo County Office of Education (SLOCOE) oversees the Arroyo Grande Community School, a public alternative school, within the city limits. In addition to these public schools, there are seven private schools in the city. The closest school to the project site is Village Preschool, located less than 0.1 mile southwest of the project site on Traffic Way. Parks. Ten City parks, a 26-acre sports complex, and a community garden are located within the city of Arroyo Grande. Kiwanis Park is located directly adjacent to the project area along Olohan Alley. Park facilities are further discussed in Section XV. Recreation, below. Libraries. The Arroyo Grande Library is located approximately 1 mile northwest of the project site at 800 West Branch Street. The branch library is one of 15 county libraries. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Result in significant environmental impacts from construction associated with the provision of new or physically altered governmental facilities, or the need for new or physically altered governmental facilities, to maintain acceptable service ratios, response times, or other performance objectives for any of the public services: Fire protection? Police protection: Schools? Parks? Other public facilities? INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 65 of 100 Discussion a) No significant project-specific impacts to public services or utilities would occur. The project would not change the existing type or intensity of land use (a bridge) and would not increase long-term demands on sheriff, fire, or emergency response services. Temporary detours would be necessary during bridge rehabilitation, but adequate alternative routes for emergency response services and access are available within 0.25 mile of the project site. The project would not induce population growth or increase demands on local schools, roads, parks, or other public facilities. Therefore, impacts would be less than significant. Mitigation Measures and Residual Impacts No significant impacts to public services were identified; therefore, no mitigation measures are necessary. XV. Recreation Environmental Setting The City of Arroyo Grande supports various community and neighborhood parks, as well as multiple designated bikeways and recreational paths. Recreational uses include a 26-acre sports complex that offers lighted tennis courts, little league and softball fields, and soccer and football fields; 10 City parks that offer a variety of active and passive uses, including picnics, barbeques, playgrounds, and entertainment areas; an off-leash dog park; and a community garden. There are also hiking and walking trails along Arroyo Grande Creek and within the James Way Oak Habitat and Wildlife Preserve. Kiwanis Park is located immediately east of the Bridge Street Bridge. Access and temporary use of Kiwanis Park is necessary for the project. The park provides the best access due to gradual slopes and undeveloped area that would not require eliminating northern parking places during construction. No permanent changes are proposed for this area under the proposed project. Bridge Street is designated as a Class III route in the City’s bicycle master plan. This bike route was signed in 2001 as part of the City’s Prop 116 Bikeway One project. The bike route is currently being signed across the bridge, down Olohan Alley to Mason Street, and then up to East Branch Street to the east. However, the City of Arroyo Grande Bike and Trails Master Plan shows the route extending along Bridge Street up to East Branch Street. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Increase the use of existing neighborhood and regional parks or other recreational facilities, such that substantial physical deterioration of the facility would occur or be accelerated? b) Include recreational facilities or require the construction or expansion of recreational facilities that might have an adverse physical effect on the environment? INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 66 of 100 Discussion a), b) Temporary access and use of Kiwanis Park would be necessary during project construction. The existing bike pathway would be temporarily closed throughout a portion of the project construction schedule. Mitigation measures have been identified to ensure that the proposed project would not result in adverse effects to the park or existing recreational bikeways during construction. Therefore, recreation-related impacts would be less than significant with mitigation. Mitigation Measures and Residual Impacts To minimize potential significant impacts to recreation facilities, the following measures would be implemented. REC/mm-1 Construction activities shall be scheduled and conducted to minimize closure of Kiwanis Park to the greatest extent possible. Kiwanis Park will only be closed when necessary for contractor access, and will remain open to the public through the duration of construction activities. All park recreational features affected by construction, such as picnic benches, will be relocated or replaced outside of the construction limits; these features will be available for use in adjacent areas during the duration of construction activities. Access to the park will be temporarily relocated from the west to the east side of the park during any closure. The City of Arroyo Grande Public Works Department will designate several parking places for park use and avoid construction activities that would impact access to these spaces. A detour along Traffic Way will be signed throughout the duration of construction activities to allow bicyclists continued access to their desired destination. With the incorporation of this measure, residual impacts associated with recreation would be less than significant. XVI. Transportation/Traffic Environmental Setting Regional access in the project vicinity is provided by US 101, a major freeway of statewide importance that traverses north-south through the Central Coast. The project site is surrounded by arterial and collector streets that provide access to the Village Core of Arroyo Grande. Traffic Way is a local arterial street that provides a link between US 101 and the Village Core of Arroyo Grande in the northwest to southeast direction. Nelson Street, located just south of the project site, is considered a collector street and provides connectivity between the Village Core and northern regions of the city. Branch Street, located just north of the project area, is considered a major arterial and provides connectivity in an east to west direction between the northern region of the city to the Village Core and US 101. West Branch Street provides access between US 101 and the Village Core commercial district located east of the freeway. The Arroyo Grande Circulation Element specifies a Level of Service (LOS) C or better on all streets and controlled intersections within the city. Where LOS D exists, policies in the Circulation Element direct the City to plan improvements to achieve LOS C or better. Public transportation facilities within the project area include Regional Transit Authority stops along East Branch Street near Traffic Way and Mason Street. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 67 of 100 Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Cause a substantial increase in traffic, in relation to existing traffic and the capacity of the street system (i.e., a substantial increase in either the number of vehicle trips, the volume to capacity ratio on roads, or congestion at intersections)? b) Exceed, individually or cumulatively, the level of service standards established by the county congestion management agency for designated roads or highways? c) Cause a change in air traffic patterns, including either an increase in traffic levels or a change in location, that results in substantial safety risks? d) Contain a design feature (e.g., sharp curves or a dangerous intersection) or incompatible uses (e.g., farm equipment) that would substantially increase hazards? e) Result in inadequate emergency access? f) Result in inadequate parking capacity? g) Conflict with adopted policies, plans, or programs supporting alternative transportation (e.g., bus turnouts, bicycle racks)? Discussion a) – d), g) The proposed project is consistent with applicable local and regional transportation plans, including the City of Arroyo Grande General Plan and 2014 Regional Transportation Plan (San Luis Obispo Council of Governments 2014). The project is intended to improve public safety, reduce future bridge maintenance costs, and preserve the historic character of the Bridge Street Bridge. If the bridge is not rehabilitated, the condition will continue to deteriorate and eventually bridge closure would be required. The proposed project would be beneficial to the long-term circulation patterns of the city. The proposed project would rehabilitate an existing bridge in the same location, retaining the historic pony truss structure and maintaining existing traffic lane capacity—a small two-lane facility retaining its scale and height. The project would not increase the capacity of the bridge or generate any increase in operational traffic trips. The project would generate a small number of additional construction-related traffic trips for heavy equipment, material hauling, and worker trips, but these would be short term and existing roadways have adequate capacity to accommodate these trips. The project would not create unsafe conditions but would improve public safety and emergency access through the proposed bridge improvements. The project would not conflict with any congestion management program or any plans or programs regarding public transit, bicyclist, or pedestrian facilities. Bikeway detours will be posted throughout construction and upon completion of the project, INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 68 of 100 pedestrians and bicyclists would have the same access as existing conditions to cross on the bridge. The project would not affect air traffic patterns. Short-term construction activities would likely cause increased congestion throughout the project area due to temporary road closures associated with Bridge Street. However, these impacts would be short- term and minimized to the extent feasible through adherence to standard Caltrans road construction standards and BMPs contained in the Caltrans Standard Specifications 2015 manual and City measures contained in the General Plan. The project would not change long-term traffic conditions within the project area; therefore, operational impacts to traffic and level of service standards would be less than significant. Therefore, impacts would be less than significant. e) Rehabilitation of the Bridge Street Bridge will require bridge closure during the construction phase of the project, prohibiting direct access from across Bridge Street to and from the downtown Village. Alternate routes are available within 0.25 mile of the project site; however, temporary closures on Bridge Street could result in temporary delays in emergency response to surrounding areas. Implementation of identified mitigation, including notification to emergency providers, would minimize short-term impacts to emergency response. Potential impacts would be less than significant with mitigation. f) Project development would result in temporary impacts to the parking area of Arroyo Grande IOOF Hall located on 128 Bridge Street, just southwest of the project site, and along Olohan Alley. Parking impacts would be limited to the duration of construction and adequate additional parking is available in multiple locations throughout the Village Core. Therefore, impacts would be less than significant Mitigation Measures and Residual Impacts To minimize potential significant impacts from temporary road closures during construction activities, the following measures would be implemented. TT/mm-1 Prior to any road closures, the City of Arroyo Grande shall provide notice to all residents, business owners, and public facilities within 500 feet of the proposed project. The notice shall include the following information: dates of construction, temporary road closures and detours, removal of parking spaces, and contact information including the phone and email address of the City of Arroyo Grande staff person responsible for responding to and addressing public complaints regarding noise, air emissions, and any other issues. The notice shall be provided at least 2 weeks prior to any planned road closure. In addition, the notice shall be posted on the City of Arroyo Grande’s website and Facebook page. With the incorporation of this measure, residual impacts associated with transportation/traffic would be less than significant. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 69 of 100 XVII. Tribal Cultural Resources Environmental Setting As discussed in Section V. Cultural Resources, the project vicinity was inhabited by speakers of the Obispeño language of the Chumash language family. The entire project area was surveyed for archaeological resources through preparation of the ASR. No archaeological resources were identified. The Bridge Street Bridge was determined eligible for listing in the NRHP in 1985 as a result of the Caltrans Historic Bridge Inventory, which was confirmed in the Caltrans Historic Bridge Inventory update project conducted in early 2000s. The Caltrans Historic Bridge Inventory concluded that the Bridge Street Bridge was eligible for listing in the NRHP under Criterion C as it embodied the distinctive characteristics of type, period, and method of construction. Built in 1908, the structure is a minor example of the American Bridge Company, a significant bridge building firm, and the bridge is an early example of a steel pin-connected pony truss. Two additional structures within the vicinity of the bridge are also designated historic properties: the Olohan Building (located less than 75 feet northwest of the existing bridge) and the IOOF Hall (located less than 75 feet southwest of the existing bridge). These properties are from the second wave of development in Arroyo Grande associated with commercial and transportation growth near the turn of the twentieth century. The IOOF Hall was listed in the NRHP in 1991. The building, constructed in 1902, is significant under Criterion C for its type, period, and method of construction as an important “embodiment of the fraternal hall format” (JRP Historical Consulting 2015). The HRER determined that the Olohan Building also meets the criteria for listing in the NRHP or CRHR. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Cause a substantial adverse change in the significance of a tribal cultural resource, defined in Public Resources Code section 21074 as either a site, feature, place, cultural landscape that is geographically defined in terms of the size and scope of the landscape, sacred place, or object with cultural value to a California Native American tribe, and that is: i) Listed or eligible for listing in the California Register of Historical Resources, or in a local register of historical resources as defined in Public Resources Code section 5020.1(k), or ii) A resource determined by the lead agency, in its discretion and supported by substantial evidence, to be significant pursuant to criteria set forth in subdivision (c) of Public Resources Code Section 5024.1. In applying the criteria set forth in subdivision (c) of Public Resource Code Section 5024.1, the lead agency shall consider the significance of the resource to a California Native American tribe. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 70 of 100 Discussion a-i), a-ii) As discussed in Section V. Cultural Resources, the ASR prepared for the project area determined that six previously documented archaeological sites are located within a 0.5-mile radius. Site types include a prehistoric lithic scatter, a prehistoric campsite, a prehistoric habitation site with bedrock mortars, and a multi-component prehistoric and historic debris scatter (CA-SLO-2643/H). CA-SLO-2643/H is closest of the six previously documented archaeological resources within 0.5 mile of the archaeological APE. Previous excavations revealed that the CA-SLO-2643/H site is highly disturbed, lacked depositional integrity, and did not qualify as a historical resource as defined by CEQA. CA-SLO- 2643/H does not extend into the project area and no further consideration of the site is warranted. The remaining five archaeological resources are located more than 0.25 mile from the project area. No archaeological resources were identified within the project area. Portions of the project would require excavation in areas of native soil or at depths in subsurface areas containing native soils. The ASR concluded that the likelihood of native soils containing intact archaeological resources in the project area is low, and, given the amount of previous disturbance within APE, low geo-archaeological sensitivity, and a lack of identified tribal cultural resources, the project area is considered to have low sensitivity for the presence of buried and/or obscured resources. Standard mitigation has been proposed to ensure impacts to any unknown resources that may be encountered during project development would be minimized. Additionally, the City has sent the notices required for consideration of tribal cultural resources consistent with AB 52. Therefore, potential impacts associated with tribal cultural resources would be less than significant with mitigation Mitigation Measures and Residual Impact To minimize potential significant impacts related to tribal cultural resources, the following measure would be implemented. Implement Mitigation Measures CUL/mm-1. With the incorporation of this measure, residual impacts related to tribal cultural resources would be less than significant. XVIII. Utilities and Service Systems Environmental Setting Utilities in Arroyo Grande are served by both the City and other regional entities. The utilities present on the Bridge Street Bridge are owned by the City and include a 6-inch-diameter ductile iron water supply line and an 8-inch-diameter ductile iron sanitary sewer line that were upgraded in 1997. Temporary utility relocations would be required during construction. Water and wastewater services within the city are provided by the City of Arroyo Grande Public Works Department. The City has a franchise agreement with South County Sanitary Service for collection, diversion, and disposal of solid waste and is served by the Cold Canyon Landfill located approximately 4.0 miles north of the City in unincorporated San Luis Obispo County. The Cold Canyon Landfill has an annual throughput of 100,000 to 249,000 tons per year and an annual capacity of 200,000 to 499,999 tons per year (California Department of Resources Recycling and Recovery [CalRecycle] 2017). As of 2015, the Cold Canyon Landfill has 14,500,000 cubic yards of capacity remaining out of its total INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 71 of 100 maximum permitted capacity of 23,900,000 cubic yards (approximately 60% available capacity remaining) (CalRecycle 2017). The estimated closure date for this landfill is 2040. Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Exceed wastewater treatment restrictions or standards of the applicable Regional Water Quality Control Board? b) Require or result in the construction of new water or wastewater treatment facilities or expansion of existing facilities? Would the construction of these facilities cause significant environmental effects? c) Require or result in the construction of new storm water drainage facilities or expansion of existing facilities? d) Have sufficient water supplies available to serve the project from existing entitlements and resources or are new or expanded entitlements needed? e) Result in a determination, by the wastewater treatment provider that serves or may serve the project, that it has adequate capacity to service the project’s anticipated demand, in addition to the provider’s existing commitments? f) Be served by a landfill with sufficient permitted capacity to accommodate the project’s solid waste disposal needs? g) Comply with federal, state, and local statutes and regulations as they relate to solid waste? Discussion a), e) The project does not propose use or development of any on-site wastewater disposal systems or connection to any community wastewater system. The project would not include any use that would require wastewater discharges, except for short-term construction activities that would be serviced by on-site portable restroom and hand-washing facilities and/or existing facilities within the project area. Therefore, potential impacts would be less than significant. b), d) The project does not propose any new use that would create demand for new water or wastewater treatment facilities and would not require the construction or expansion of these facilities. Short-term construction activities would be served by the City’s municipal water supply and portable wastewater facilities and/or existing facilities within the project area. INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 72 of 100 Therefore, potential impacts would be less than significant. c) The project will comply with all applicable requirements outlined in the City of Arroyo Grande’s Storm Water Management Program and will satisfy PR1 (Site Design and Runoff Reduction) and PR2 (Water Quality Treatment) of the Central Coast RWQCB’s Post-Construction Storm Water Management Requirements (Resolution R3-20132-0032025). The City proposes to meet PR1 and PR2 requirements on-site to ensure reduction of pollutant discharges to the maximum extent practicable and prevent stormwater discharges from causing or contributing to a violation of receiving water quality standards. The project would result in 1 acre or more of ground disturbance; therefore, the City would be required to prepare a Storm Water Pollution Prevention Plan (SWPPP) pursuant to SWRCB requirements. The project does not propose substantial changes in long-term use of the project area, and no permanent or substantial changes to drainage patterns or facilities would occur. Therefore, impacts would be less than significant. f), g) Upon completion, operation and use of the project would not generate any solid waste. Construction activities would result in the generation of solid waste materials, including cut volumes and demolition of existing infrastructure. The proposed project will be served by the Cold Canyon Landfill, which has adequate permitted capacity to serve the project. Therefore, impacts would be less than significant. Mitigation Measures and Residual Impacts No significant impacts to utilities and service systems were identified; therefore, no mitigation measures are necessary. 5. Mandatory Findings of Significance Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact a) Substantially degrade the quality of the environment, substantially reduce the habitat of a fish or wildlife species; cause a fish or wildlife population to drop below self-sustaining levels; threaten to eliminate a plant or animal community; substantially reduce the number or restrict the range of an endangered, rare or threatened species; or eliminate examples of the major periods of California history or prehistory? b) Have the potential to achieve short-term environmental goals to the disadvantage of long-term environmental goals? INITIAL STUDY MITIGATED NEGATIVE DECLARATION Bridge Street Bridge Rehabilitation Project July 2017 Page 73 of 100 Would the project: Potentially Significant Impact Less Than Significant with Mitigation Less Than Significant Impact No Impact c) Have possible environmental effects that are individually limited but cumulatively considerable? “Cumulatively considerable” means that the incremental effects of an individual project are significant when viewed in connection with the effects of past projects, the effects of other current projects, and the effects of possible future projects. d) Cause substantial adverse effects on human beings, either directly or indirectly? Discussion a) The proposed project does not have the potential to substantially degrade the quality of the environment. Implementation of the mitigation measures would ensure that the project would not substantially reduce the habitat of a fish or wildlife species, cause a fish or wildlife population to drop below self-sustaining levels or threaten to eliminate a plant or animal community, or substantially reduce the number or restrict the range of a rare or endangered plant or animal. The proposed project would not contribute significantly to GHG emissions or significantly increase energy consumption, and would not eliminate important examples of the major periods of California history or prehistory. Therefore, impacts would be less than significant with mitigation described within each issue area. b) The proposed project is designed to achieve the goal of the City to improve safety and operations within the highway and local roadway system. The proposed project does not have the potential to achieve short-term goals to the disadvantage of long-term environmental goals. Therefore, impacts would be less than significant. c) The project does not propose a new or significantly different use within the project site; therefore, the project’s impacts would be limited in extent and duration and could be generally minimized through application of standard control measures. The proposed project does not have impacts that would be individually limited but cumulatively considerable with implementation of identified mitigation. There are no proposed or planned projects in the area that would create similar impacts, which, when considered together with the project-related impacts, would be considerable, or which compound or increase other long-term environmental impacts. Therefore, impacts would be less than significant with mitigation described within each issue area. d) The proposed project would not create environmental effects that would cause substantial adverse effects on human beings, either directly or indirectly. The project would improve existing infrastructure, providing beneficial impacts on existing traffic and circulation systems. Adverse project effects would generally be limited to the construction phase of the project and minimized through identified mitigation measures. Therefore, impacts would be less than significant with mitigation described within each issue area. INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 74 of 100 6. Mitigation Monitoring and Reporting Program Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party Air Quality AQ/mm-1 Prior to issuance of construction permits, the following measures shall be incorporated into the construction phase of the project and shown on all applicable plans: Construction Equipment a. Maintain all construction equipment in proper tune according to manufacturer’s specifications; b. Fuel all off-road and portable diesel powered equipment with California Air Resources Board- certified motor vehicle diesel fuel (non-taxed version suitable for use off-road); c. Use diesel construction equipment meeting the California Air Resources Board’s Tier 2 certified engines or cleaner off-road heavy-duty diesel engines, and comply with the State off-Road Regulation; d. Use on-road heavy-duty trucks that meet the California Air Resources Board’s 2007 or cleaner certification standard for on-road heavy-duty diesel engines, and comply with the State On-Road Regulation; e. Construction or trucking companies with fleets that that do not have engines in their fleet that meet the engine standards identified in the above two measures (e.g., captive or oxides of nitrogen exempt area fleets) may be eligible by proving alternative compliance; f. All on- and off-road diesel equipment shall not idle for more than 5 minutes. Signs shall be posted in the designated queuing areas and or job sites to remind drivers and operators of the 5-minute idling limit; Confirm inclusion of these measures on all applicable plans and inspect project site during construction activities to confirm implementation of construction control measures Prior to issuance of construction permits and during construction activities City of Arroyo Grande Community Development Department INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 75 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party g. Diesel idling shall be avoided to the greatest extent feasible throughout the duration of construction activities. No idling in excess of 5 minutes shall be permitted as described above; h. Staging and queuing areas shall not be located within 1,000 feet of sensitive receptors whenever possible; i. Electrify equipment when feasible; j. Substitute gasoline-powered in place of diesel- powered equipment, where feasible; and, k. Use alternatively fueled construction equipment on- site where feasible, such as compressed natural gas (CNG), liquefied natural gas (LNG), propane, or biodiesel. AQ/mm-2 Upon application for construction permits, all required PM10 measures shall be shown on applicable grading or construction plans, and made applicable during grading and construction activities as described below. a. Reduce the amount of the disturbed area where possible; b. Use of water trucks or sprinkler systems in sufficient quantities to prevent airborne dust from leaving the site and from exceeding the San Luis Obispo County Air Pollution Control District’s limit of 20% opacity for greater than 3 minutes in any 60-minute period. Increased watering frequency would be required whenever wind speeds exceed 15 miles per hour. Reclaimed (non-potable) water should be used whenever possible; c. All dirt stock pile areas should be sprayed daily or covered with tarps or other dust barriers, as needed; d. Permanent dust control measures identified in the approved project revegetation and landscape plans Confirm inclusion of these measures on all applicable plans and inspect project site during construction activities to confirm implementation of construction control measures Prior to issuance of construction permits and during construction activities City of Arroyo Grande Community Development Department INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 76 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party should be implemented as soon as possible following completion of any soil-disturbing activities; e. Exposed ground areas that are planned to be reworked at dates greater than 1 month after initial grading should be sown with a fast germinating, non-invasive grass seed and watered until vegetation is established; f. All disturbed soil areas not subject to revegetation should be stabilized using approved chemical soil binders, jute netting, or other methods approved in advance by the San Luis Obispo County Air Pollution Control District; g. All roadways, driveways, sidewalks, etc. to be paved should be completed as soon as possible. In addition, building pads should be laid as soon as possible after grading unless seeding or soil binders are used; h. Vehicle speed for all construction vehicles shall not exceed 15 miles per hour on any unpaved surface at the construction site; i. All trucks hauling dirt, sand, soil, or other loose materials are to be covered or should maintain at least 2 feet of freeboard (minimum vertical distance between top of load and top of trailer) in accordance with California Vehicle Code Section 23114; j. Install wheel washers or other devices to control tracking of mud and dirt onto adjacent roadways where vehicles enter and exit unpaved roads onto streets, or wash off trucks and equipment leaving the site; k. Sweep streets at the end of each day if visible soil material is carried onto adjacent paved roads. Water sweepers with reclaimed water should be used INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 77 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party where feasible. Roads shall be pre-wetted prior to sweeping when feasible; l. The contractor or builder shall designate a person or persons to monitor the fugitive dust emissions and enhance the implementation of the measures as necessary to minimize dust complaints, reduce visible emissions below the San Luis Obispo County Air Pollution Control District’s limit of 20% opacity for greater than 3 minutes in any 60-minute period, and to prevent transport of dust off-site. Their duties shall include holidays and weekend periods when work may not be in progress. The name and telephone number of such persons shall be provided to the San Luis Obispo County Air Pollution Control District Engineering & Compliance Division prior to the start of any grading, earthwork, or demolition. Biological Resources BIO/mm-1 Prior to construction, the City of Arroyo Grande Public Works Department will obtain a Section 404 Permit from the United States Army Corps of Engineers, a Section 401 Water Quality Certification from the Regional Water Quality Control Board, and a Section 1602 Streambed Alteration Agreement from the California Department of Fish and Wildlife for project- related impacts that will occur in areas under federal and state jurisdiction. The City of Arroyo Grande Public Works Department will obtain all necessary permits Prior to initiation of project construction The City of Arroyo Grande Public Works Department BIO/mm-2 Prior to construction, the City of Arroyo Grande Public Works Department will retain a qualified biological monitor(s) to monitor construction and ensure compliance with the avoidance and minimization efforts outlined within all the project environmental documents. At a minimum, monitoring will occur during initial ground disturbance activities and vegetation removal within the Arroyo Grande Creek corridor. Monitoring may be reduced to part time once initial Confirm that a qualified biological monitor has been retained for construction monitoring Prior to initiation of project construction The City of Arroyo Grande Public Works Department INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 78 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party disturbance and vegetation removal activities are complete. The duration of monitoring should be at least once per week throughout the remaining construction phases, unless specified otherwise by permitting agencies. BIO/mm-3 Prior to construction, all construction personnel will participate in an environmental awareness training program conducted by a qualified biologist. At a minimum, the program shall include: descriptions of the special-status species that have potential to occur in the project area; their habitat requirements and life histories as they relate to the project; the avoidance, minimization, and mitigation measures that will be implemented to avoid impacts to the species and their habitats; the regulatory agencies and regulations that manage their protection; and consequences that may result from unauthorized impacts or take of special- status species and their habitats. Subsequent trainings shall be provided as needed for additional construction workers through the duration of construction activities. Subsequent trainings shall include, at minimum, a review of the training materials (i.e., a PowerPoint presentation or handouts prepared by the qualified biologist) and a signed acknowledgement that the construction worker has reviewed and understands the training materials. The training materials shall identify an on-site primary point of contact for all questions related to the environmental awareness training and actions required under the training program and shall include contact information for that primary on-site contact. Confirm that all construction personnel participate in an environmental awareness training program conducted by a qualified biologist. Prior to initiation of project construction The City of Arroyo Grande Public Works Department BIO/mm-4 Construction activities within jurisdictional areas will be conducted during the dry season when stream flows will be at annual lows (June 15 through October 31) in any given year, or as otherwise directed by the regulatory agencies. Deviations from this work window can be made with permission from the relevant regulatory agencies. Confirm inclusion of this measure on all applicable plans and confirm appropriate timing of project implementation. Prior to issuance of construction permits and during construction activities. The City of Arroyo Grande Public Works Department INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 79 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party BIO/mm-5 Prior to initiation of any construction activities, including vegetation clearing or grubbing, sturdy high-visibility fencing will be installed to protect the jurisdictional areas adjacent to the designated work areas. This fencing will be placed so that unnecessary adverse impacts to the adjacent habitats are avoided. No construction work (including storage of materials) will occur outside of the specified project limits. The fencing will remain in place during the entire construction period, be monitored periodically by a qualified biologist, and be maintained as needed by the contractor. Confirm that sturdy high-visibility fencing (Environmentally Sensitive Area fencing) has been installed. Prior to initiation of any construction activities The City of Arroyo Grande Public Works Department BIO/mm-6 Prior to construction, a Storm Water Pollution Prevention Plan will be prepared for the project. Provisions of this plan will be implemented during and after construction. Construction personnel will be informed of the importance of preventing spills, the appropriate measures to take should a spill occur, and the measures necessary to avoid and minimize erosion and stormwater pollution in and near the work area. Confirm that a SWPPP has been prepared for the project and all associated BMPs are implemented. Prior to initiation of any construction activities The City of Arroyo Grande Public Works Department BIO/mm-7 Prior to construction, the contractor will prepare a Hazardous Materials Response Plan to allow for a prompt and effective response to any accidental spills. Workers will be informed of the importance of preventing spills and of the appropriate measures to take should a spill occur. Confirm that a Hazardous Materials Response Plan has been prepared. Prior to initiation of any construction activities The City of Arroyo Grande Public Works Department INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 80 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party BIO/mm-8 During construction, erosion control measures (e.g., silt fencing, fiber rolls, barriers) will remain available on-site and will be utilized as necessary to prevent erosion and sedimentation in jurisdictional areas. No synthetic plastic mesh products will be used for erosion control and use of these materials on-site is prohibited. Erosion control measures and other suitable Best Management Practices used will be checked to ensure that they are intact and functioning effectively and maintained on a daily basis throughout the duration of construction. The contractor will also apply adequate dust control techniques, such as site watering, during construction to protect water quality. Confirm that erosion control BMPs are intact and functioning effectively Throughout the duration of construction activities The City of Arroyo Grande Public Works Department and the Contractor BIO/mm-9 During construction, the cleaning and refueling of equipment and vehicles will occur only within a designated staging area and at least 60 feet (20 meters) from jurisdictional other waters or other aquatic areas. At a minimum, equipment and vehicles will be checked and maintained on a daily basis to ensure proper operation and avoid potential leaks or spills. Confirm that a plan is in place for prompt and effective response to any accidental spills. Prior to initiation of project construction and throughout the duration of construction activities The City of Arroyo Grande Public Works Department and the Contractor BIO/mm-10 During construction, trash will be contained, removed from the work site, and disposed of regularly. Following construction, trash and construction debris will be removed from the work areas. Vegetation removed from the construction site will be taken to a certified landfill to prevent the spread of invasive species. If soil from weedy areas (such as areas with poison hemlock or other invasive exotic plant species) must be removed off-site, the top 6 inches (152 millimeters) containing the seed layer in areas with weedy species will be disposed of at a permitted landfill. Confirm compliance through site verification. Throughout the duration of construction activities The City of Arroyo Grande Public Works Department and the Contractor BIO/mm-11 During construction, no pets will be allowed on the construction site. Confirm compliance through site verification. Throughout the duration of construction activities Contractor INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 81 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party BIO/mm-12 Prior to construction, the City of Arroyo Grande Public Works Department will prepare a comprehensive Habitat Mitigation and Monitoring Plan that provides for a 1:1 restoration ratio for temporary impacts and a 3:1 enhancement ratio for permanent impacts, unless otherwise directed by regulatory agencies. To the extent feasible, mitigation activities will be implemented within the project area and/or the Arroyo Grande Creek riparian corridor and in areas in and adjacent to the project area that support exotic species, contain agricultural trash, and have erosion. These areas provide the most optimal mitigation opportunities on-site. Any revegetation will be conducted using only native plant species. The final Habitat Mitigation and Monitoring Plan will identify the specific mitigation sites and it will be implemented immediately following project completion. Confirm that a HMMP has been prepared for the project. Prior to initiation of project construction The City of Arroyo Grande Public Works Department BIO/mm-13 During construction, the project will make all reasonable efforts to limit the use of imported soils for fill. Soils currently existing on-site should be used for fill material. If the use of imported fill material is necessary, the imported material must be obtained from a source that is known to be free of invasive plant species, or the material must consist of purchased clean material such as crushed aggregate, sorted rock, or similar. To avoid the spread of invasive species, the contractor shall: a. Stockpile topsoil and redeposit the stockpiled soil on-site at a sufficient depth to preclude germination or spread of those species after construction is complete; or, b. Transport the topsoil to a permitted landfill for disposal. Confirm compliance through site verification. Throughout the duration of construction activities The City of Arroyo Grande Public Works Department INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 82 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party BIO/mm-14 Prior to construction, project plans will clearly identify the type of species, location, and methodology of removal and disposal of invasive exotic species found within the project site. Removal and disposal of invasive exotic plants and wildlife must be in accordance with state law and/or project authorizations from resource agencies (e.g., USFWS Programmatic Biological Opinion). In particular, for those invasive exotic plant species that are particular difficult to remove (e.g., jubata grass [Cortaderia jubata]), a combination of cutting and application of herbicide would likely be required, and thus require a request for an amendment to the standard conditions of the USFWS Programmatic Biological Opinion. In addition, removal of crayfish or bullfrog must be conducted lawfully using methodologies outlined in the California Fish and Game Code. Confirm inclusion of this information on all applicable plans and confirm appropriate timing of project implementation. Prior to issuance of construction permits and during construction activities. The City of Arroyo Grande Public Works Department BIO/mm-15 During construction, the biological monitor(s) will ensure that the spread or introduction of invasive exotic plant and wildlife species is avoided to the maximum extent possible. Confirm compliance through site verification. Throughout the duration of construction activities City of Arroyo Grande Public Works Department and Biological Monitor BIO/mm-16 All erosion control materials including straw bales, straw wattles, or mulch used on-site must be free of invasive species seed. Confirm compliance through site verification. Throughout the duration of construction activities City of Arroyo Grande Public Works Department and Biological Monitor BIO/mm-17 In-stream work will take place between June 15 and October 31 in any given year, when the surface water within Arroyo Grande Creek is likely to be at seasonal minimum. Deviations from this work window will only be made with permission from the relevant regulatory agencies. During in-stream work, a qualified biologist that is approved by the National Oceanic and Atmospheric Administration National Marine Fisheries Service and has experience in steelhead biology and ecology, aquatic habitats, biological monitoring (including diversion/dewatering), and capturing, handling, and Retain a NMFS- approved biologist and confirm compliance through site verification. During in-stream work The City of Arroyo Grande Public Works Department INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 83 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party relocating fish species will be retained. During in-stream work, the biological monitor(s) will continuously monitor placement and removal of any required stream diversions and will capture stranded steelhead and other native fish species and relocate them to suitable habitat, as appropriate. The approved biologist(s) will capture steelhead stranded as a result of diversion/dewatering and relocate steelhead to the nearest suitable in-stream habitat. The approved biologist(s) will note the number of steelhead observed in the affected area, the number of steelhead relocated, and the date and time of the collection and relocation. BIO/mm-18 During in-stream work, if pumps are incorporated to assist in temporarily dewatering the site, intakes will be completely screened with no larger than 0.2-inch (5-millimeter) wire mesh to prevent steelhead and other sensitive aquatic species from entering the pump system. Pumps will release the diverted water so that suspended sediment will not re- enter the stream. The form and function of pumps used during the dewatering activities will be checked daily, at a minimum, by a qualified biological monitor to ensure a dry work environment and minimize adverse effects to aquatic species and habitats. Confirm compliance through site verification. During construction during in-stream work City of Arroyo Grande Public Works Department and Biological Monitor BIO/mm-19 Only United States Fish and Wildlife Service-approved biologists will participate in activities associated with the capture and handling of California red-legged frogs. Biologists authorized under the Programmatic Biological Opinion do no need to resubmit their qualifications for subsequent projects conducted pursuant to the Programmatic Biological Opinion, unless the United States Fish and Wildlife have revoked their approval at any time during the life of the Programmatic Biological Opinion. Retain a USFWS- approved biologist and confirm compliance with this measure through site verification. Throughout the duration of construction activities City of Arroyo Grande Public Works Department and Caltrans INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 84 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party BIO/mm-20 Ground disturbance will not begin until written approval is received from the United States Fish and Wildlife Service that the biologist(s) is qualified to conduct the work. The California Department of Transportation will request approval of the biologist(s) from the United States Fish and Wildlife Service. Obtain written approval from the USFWS Prior to initiation of project construction City of Arroyo Grande Public Works Department and Caltrans BIO/mm-21 A United States Fish and Wildlife Service-approved biologist will survey the project area no more than 48 hours before the onset of work activities. If any life stage of the California red- legged frog is found and these individuals are likely to be killed or injured by work activities, the approved biologist will be allowed sufficient time to move them from the site before work activities begin. The United States Fish and Wildlife Service-approved biologist will relocate the California red- legged frogs the shortest distance possible to a location that contains suitable habitat and will not be affected by the activities associated with the project. The relocation site should be in the same drainage to the extent practicable. The California Department of Transportation will coordinate with the United States Fish and Wildlife Service on the relocation site prior to the capture of any California red-legged frogs. Retain a USFWS- approved biologist and confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department and Caltrans BIO/mm-22 A United States Fish and Wildlife Service-approved biologist will be present at the work site until California red-legged frogs have been relocated out of harm’s way, workers have been instructed, and disturbance of the habitat has been completed. After this time, the City of Arroyo Grande Public Works Department will designate a person to monitor on-site compliance with minimization measures. The United States Fish and Wildlife Service-approved biologist will ensure that this monitor receives the training outlined in BIO/mm-3 above and in the identification of California red-legged frogs. If the monitor or the United States Fish and Wildlife Service- approved biologist recommends that work be stopped because California red-legged frogs would be affected in any Retain a USFWS- approved biologist and confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department and Caltrans INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 85 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party manner, they will notify the resident engineer (the engineer that is directly overseeing and in command of construction activities) immediately. The resident engineer will either resolve the situation by eliminating the adverse effect immediately or require that actions that are causing these effects be halted. If work is stopped, the California Department of Transportation, City of Arroyo Grande Public Works Department, and United States Fish and Wildlife Service will be notified as soon as is reasonably possible. BIO/mm-23 During project activities, trash that may attract predators will be properly contained, removed from the work site, and disposed of regularly. Following construction, trash and construction debris will be removed from work areas. Confirm compliance through site verification. Throughout the duration of construction activities City of Arroyo Grande Public Works Department and Contractor BIO/mm-24 All refueling, maintenance, and staging of equipment and vehicles will occur at least 60 feet from riparian habitat or water bodies and in a location from where a spill would not drain directly toward aquatic habitat (e.g., on a slope that drains away from the water). The monitor will ensure contamination of habitat does not occur during such operations. Prior to the onset of work, the City of Arroyo Grande Public Works Department will ensure that a plan is in place for prompt and effective response to any accidental spills. All workers will be informed of the importance of preventing spills and of the appropriate measures to take should a spill occur. Confirm inclusion of this information on all applicable plans and confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department and biological monitor BIO/mm-25 Habitat contours will be returned to their original configuration at the end of project activities. This measure will be implemented in all areas disturbed by activities associated with the project, unless the United States Fish and Wildlife, California Department of Transportation, and City of Arroyo Grande Public Works Department determine that it is not feasible or modification of original contours would benefit the California red-legged frog. Confirm compliance with this measure through site verification. Following completion of project construction activities City of Arroyo Grande Public Works Department and Caltrans INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 86 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party BIO/mm-26 The number of access routes, size of staging areas, and the total area of activity will be limited to the minimum necessary to achieve the project. Environmentally Sensitive Areas will be established to confine access routes and construction areas to the minimum area necessary to complete construction, and minimize the impact to California red-legged frog habitat; this goal includes locating access routes and construction areas outside of wetlands and riparian areas to the maximum extent practicable. Confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department BIO/mm-27 The City of Arroyo Grande Public Works Department will attempt to schedule work for times of the year when impacts to the California red-legged frog would be minimal. For example, work that would affect large pools that may support breeding would be avoided, to the maximum degree practicable, during the breeding season (November through May). Isolated pools that are important to maintain California red-legged frogs through the driest portions of the year would be avoided, to the maximum degree practicable, during the late summer and early fall. Habitat assessments, surveys, and technical assistance between the California Department of Transportation and United States Fish and Wildlife Service during project planning will be used to assist in scheduling work activities to avoid sensitive habitats during key times of year. Confirm compliance with this measure through appropriate timing of construction activities. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department BIO/mm-28 To control sedimentation during and after project implementation, the City of Arroyo Grande Public Works Department will implement Best Management Practices outlined in any authorizations or permits issued under the authorities of the Clean Water Act that it receives for the specific project. Confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 87 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party BIO/mm-29 If a work site is to be temporarily dewatered by pumping, intakes will be completely screened with wire mesh not larger than 0.2 inch to prevent California red-legged frogs from entering the pump system. Water will be released downstream at an appropriate rate to maintain downstream flows during construction. Upon completion of construction activities, any diversions or barriers to flow will be removed in a manner that would allow flow to resume with the least disturbance to the substrate. Alteration of the streambed will be minimized to the maximum extent possible; any imported material will be removed from the streambed upon completion of the project. Confirm compliance with this measure through site verification. During and following completion of construction activities City of Arroyo Grande Public Works Department BIO/mm-30 Unless approved by the United States Fish and Wildlife Service, water will not be impounded in a manner that may attract California red-legged frogs. Obtain approval for impoundments from the USFWS, if necessary Throughout the duration of construction activities City of Arroyo Grande Public Works Department and Caltrans BIO/mm-31 A United States Fish and Wildlife Service-approved biologist will permanently remove any individuals of exotic species, such as bullfrogs, crayfish, and centrarchid fishes from the project area, to the maximum extent practicable. The United States Fish and Wildlife Service-approved biologist will be responsible for ensuring their activities are in compliance with the California Fish and Game Code. Retain a USFWS- approved biologist and confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department and Caltrans BIO/mm-32 If the City of Arroyo Grande Public Works Department demonstrates that disturbed areas have been restored to conditions that allow them to function as habitat for the California red-legged frog, these areas will not be included in the amount of total habitat permanently disturbed. Confirm compliance with this measure through site verification. Following completion of construction activities City of Arroyo Grande Public Works Department and Caltrans BIO/mm-33 To ensure that diseases are not conveyed between work sites by the United States Fish and Wildlife Service-approved biologist, the fieldwork code of practice developed by the Declining Amphibian Task Force will be followed at all times. Confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of City of Arroyo Grande Public Works Department and biological monitor INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 88 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party construction activities BIO/mm-34 Project sites will be re-vegetated with an assemblage of native riparian, wetland, and upland vegetation suitable for the area. Locally collected plant materials will be used to the extent practicable. Invasive, exotic plants will be controlled to the maximum extent practicable. This measure will be implemented in all areas disturbed by activities within the project area, unless the United States Fish and Wildlife Service, California Department of Transportation, and City of Arroyo Grande Public Works Department have determined that it is not feasible or practical. Confirm compliance with this measure through site verification. Following completion of construction activities City of Arroyo Grande Public Works Department, Caltrans and biological monitor BIO/mm-35 The City of Arroyo Grande Public Works Department will not use herbicides as the primary method to control invasive, exotic plants. However, if the City of Arroyo Grande Public Works Department determines the use of herbicides is the only feasible method for controlling invasive plants at a specific project site, it will implement the following additional measures to protect California red-legged frog: a. The City of Arroyo Grande Public Works Department will not use herbicides during the breeding season for California red-legged frog. b. The City of Arroyo Grande Public Works Department will conduct surveys for California red-legged frog immediately prior to the start of herbicide use. If found, California red-legged frog will be relocated to suitable habitat far enough from the project area that no direct contact with herbicide would occur. c. Giant reed and other invasive plants will be cut and hauled out by hand and painted with glyphosate- based products, such as Aquamaster® or Rodeo®. d. Licensed and experienced City of Arroyo Grande staff or a licensed and experienced contractor will use a hand-held sprayer for foliar application of Confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department and biological monitor INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 89 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party Aquamaster® or Rodeo® where large monoculture stands occur at an individual project site. e. All precautions will be taken to ensure that no herbicide is applied to native vegetation. f. Foliar applications of herbicide will not occur when wind speeds are in excess of 3 miles per hour. g. No herbicides will be applied within 24 hours of forecasted rain. h. Application of herbicides will be done by a qualified City of Arroyo Grande staff or contractors to ensure that overspray is minimized, that application is made in accordance with the label recommendations, and that required and reasonable safety measures are implemented. A safe dye will be added to the mixture to visually denote treated sites. Application of herbicides will be consistent with the United States Environmental Protection Agency’s Office of Pesticide Programs Endangered Species Protection Program county bulletins. i. All herbicides, fuels, lubricants, and equipment will be stored, poured, or refilled at least 60 feet from riparian habitat or water bodies in a location where a spill would not drain directly toward aquatic habitat. The City of Arroyo Grande Public Works Department will ensure that a plan is in place for a prompt and effective response to accidental spills. All workers will be informed of the importance of preventing spills and of the appropriate measures to take should a spill occur. INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 90 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party BIO/mm-36 Prior to construction, a biologist determined qualified by the California Department of Transportation and California Department of Fish and Wildlife shall survey the project site and, if present, capture and relocate any western pond turtles to suitable habitat upstream of the project site. Observations of these or other special-status species shall be documented on California Natural Diversity Database forms and submitted to the California Department of Fish and Wildlife upon project completion. If western pond turtle or other special concern aquatic species are observed during construction, they will likewise be relocated to suitable upstream habitat by a qualified biologist. Retain a qualified biologist and verify that CNDDB forms are submitted to the CDFW, if applicable. Prior to, during, and following completion of project construction City of Arroyo Grande Public Works Department BIO/mm-37 Prior to construction, when feasible, tree removal will be scheduled to occur outside of the typical nesting bird season (February 15 through September 1), to avoid potential impacts to nesting birds. Confirm inclusion of this measure on all applicable plans and confirm appropriate timing of project implementation. Prior to issuance of construction permits and during construction activities. The City of Arroyo Grande Public Works Department and biological monitor BIO/mm-38 If construction activities are proposed during the typical nesting season (February 15 to September 1), a nesting bird survey will be conducted by qualified biologists no more than two weeks prior to the start of construction to determine presence/absence of nesting birds within 500 feet of the project site. The California Department of Transportation will be notified if federally listed nesting bird species are observed during the surveys and will facilitate coordination with the United States Fish and Wildlife Service, if necessary to determine an appropriate avoidance strategy. Likewise, coordination with California Department of Fish and Wildlife will be facilitated by the City of Arroyo Grande Public Works Department if necessary to devise a suitable avoidance plan for state-listed nesting bird species. If raptor nests are observed within 500 feet of the project area during the pre- construction nesting bird surveys, the nest(s) shall be The qualified biologist shall submit the preconstruction nesting bird survey report to the City of Arroyo Grande Public Works Department. Confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department and biological monitor INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 91 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party designated an Environmental Sensitive Area and protected by a minimum 500-foot avoidance buffer until the breeding season ends or until a qualified biologist determines that all young have fledged and are no longer reliant upon the nest or parental care for survival. Similarly, if active passerine nests are observed during the pre-construction nesting bird surveys, the nest(s) shall be designated an Environmentally Sensitive Area and protected by a minimum 250-foot avoidance buffer until the breeding season ends or until a qualified biologist determines that all young have fledged and are no longer reliant upon the nest or parental care for survival. Resource agencies may consider proposed variances from these buffers if there is a compelling biological or ecological reason to do so, such as protection of a nest via concealment due to site topography. BIO/mm-39 Prior to construction, a visual survey will be conducted by a qualified biologist, at dawn and at dusk, to identify potential roosting bat activity. This survey shall be conducted between two to four weeks prior to bridge and/or tree removal activities that are proposed to occur. If roosting bat activity is identified during the preconstruction survey process, the City of Arroyo Grande will coordinate with the California Department of Fish and Wildlife regarding the biological significance of the bat population and appropriate measures that could be used to exclude bats from roosting under the bridge. Measures may include, but are not limited to the installation of exclusionary devices by a qualified individual. The qualified biologist shall submit the preconstruction roosting bat survey report to the City of Arroyo Grande Public Works Department. Confirm compliance with this measure through site verification. Prior to initiation of project construction activities City of Arroyo Grande Public Works Department and biological monitor BIO/mm-40 If it is determined that a substantial impact to individual bat species or a maternity roost will occur, then the City of Arroyo Grande will compensate for the impact through the development and implementation of a mitigation plan in coordination with California Department of Fish and Wildlife. Develop and implement a mitigation plan and monitoring plan in coordination with California Department of Fish and Wildlife. Throughout the duration of construction activities City of Arroyo Grande Public Works Department INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 92 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party Cultural Resources CUL/mm-1 If a potentially significant cultural resource is encountered during subsurface earthwork activities, all construction activities within a 100-foot radius of the find shall cease until a qualified archaeologist determines whether the uncovered resource requires further study. A standard inadvertent discovery clause shall be included in every grading and construction contract to inform contractors of this requirement. Any previously undiscovered resources found during construction shall be recorded on appropriate California Department of Parks and Recreation forms and evaluated for significance in terms of California Environmental Quality Act criteria by a qualified archaeologist. Potentially significant cultural resources consist of, but are not limited to, stone, bone, glass, ceramic, wood, or shell artifacts; fossils; or features including hearths, structural remains, or historic dumpsites. If the resource is determined significant under the California Environmental Quality Act, the qualified archaeologist shall prepare and implement a research design and archaeological data recovery plan that will capture those categories of data for which the site is significant. The archaeologist shall also perform appropriate technical analysis, prepare a comprehensive report, and file it with the appropriate Information Center and provide for the permanent curation of the recovered materials. Confirm monitor is on- site prior to construction activities and appropriate protocol is understood and implemented. Prior to commencement of construction activities. City of Arroyo Grande Public Works Department and Caltrans Hazards and Hazardous Materials HAZ/mm-1 Prior to construction, the City of Arroyo Grande Public Works Department shall prepare a Hazardous Material Spill Prevention, Control and Countermeasure Plan to minimize the potential for, and effects of, spills of hazardous or toxic substances during construction of the project. The plan shall be submitted for review and approval by the City of Arroyo Confirm compliance with this measure through site verification. Throughout the duration of construction activities City of Arroyo Grande Public Works Department, Caltrans, and Contractor INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 93 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party Grande Public Works Director, and shall include, at minimum, the following: a. A description of storage procedures and construction site maintenance and upkeep practices; b. Identification of a person or persons responsible for monitoring implementation of the plan and spill response; c. Identification of Best Management Practices to be implemented to ensure minimal impacts to the environment occur, including but not limited to the use of containment devices for hazardous materials, training of construction staff regarding safety practices to reduce the chance for spills or accidents, and use of non-toxic substances where feasible; d. A description of proper procedures for containing, diverting, isolating, and cleaning up spills, hazardous substances and/or soils, in a manner that minimizes impacts on surface and groundwater quality and sensitive biological resources; e. A description of the actions required if a spill occurs, including which authorities to contact and proper clean-up procedures; and f. A requirement that all construction personnel participate in an awareness training program conducted by qualified personnel approved by the City of Arroyo Grande Public Works Director. The training must include a description of the Hazardous Materials Spill Prevention, Control and Countermeasure Plan, the plan’s requirements for spill prevention, information regarding the importance of preventing spills, the appropriate measures to take should a spill occur, and identification of the location of all clean-up materials and equipment. INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 94 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party HAZ/mm-2 A Soil Management Plan and Health and Safety Plan shall be developed for the project and subject to approval by the City of Arroyo Grande Public Works Department to ensure contaminated soils excavated during the project construction are handled, stockpiled, and disposed of in accordance with federal, state, and local regulations. Soils excavated during the project shall be tested for lead concentrations and the Soil Management Plan shall establish a Reuse Screening Level for the excavated soils; excavated soils with contaminant concentrations below the Reuse Screening Levels may be reused during construction on the right-of-way, while soils with contaminant concentrations exceeding the Reuse Screening Levels shall be managed as hazardous waste and disposed of at a facility that accepts soil with the detected concentrations of contaminants. Special handling, treatment, or disposal of aerially deposited lead in soils during construction activities shall be consistent with the California Department of Toxic Substances Control Lead Variance (No. V09HQSCD006) dated July 1, 2009. Prepare a Soil Management Plan and Health and Safety Plan and submit to Caltrans and the Director of the Public Works Department for approval. Prior to initiation of project construction activities City of Arroyo Grande Public Works Department HAZ/mm-3 Prior to initiation of construction, a Lead Compliance Plan shall be prepared by the contractor to prevent or minimize worker exposure to lead from handling material containing lead based paint or aerially-deposited lead (California Code of Regulations, Title 8, Section 1532.1). This plan shall also be required for work performed on painted structures. The contractor shall prepare a written, project-specific Excavation and Transportation Plan establishing procedures the contractor shall use for excavating, stockpiling, transporting, and placing (or disposing) of material containing lead-based paint or aerially-deposited lead. The plan must conform to Department of Toxic Substance Control and California Occupational Safety and Health Administration regulations. For samples where lead levels exceed hazardous waste criteria, the excavated soil shall be either managed or disposed of as a California hazardous waste or stockpiled and Prepare a Lead Compliance Plan and Excavation and Transportation Plan submit to Caltrans and the Director of the Public Works Department for approval. Prior to initiation of project construction activities City of Arroyo Grande Public Works Department, Caltrans, and Contractor INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 95 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party resampled to confirm waste classification and potential utilization of Caltrans’ hazardous waste variance agreement to recycle soil on site. The appropriate Caltrans Standard Special Provision shall be included in the Plans, Specifications, and Estimate. HAZ/mm-4 Conventional demolition techniques for painted surfaces and treated wood members shall comply with Occupational Safety and Health Administration and California Occupational Safety and Health Administration statutes regarding worker awareness training, exposure monitoring, and medical examinations, and should include a written respiratory protection program. Dust control procedures shall be implemented in compliance with California Code of Regulations, Title 8, Section 1532.1, during abatement, demolition, and/or renovation of the bridge. Pulverization and/or activities that may result in the generation of fine dust and particulates shall be prohibited at the project site. Confirm inclusion of this measure on all applicable plans and confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department, Caltrans, and Contractor HAZ/mm-5 Materials that are excavated or water that accumulates within an excavation during construction activities should not be discarded to the ground surface, watershed, or waterway. Accumulated or excavated materials should be segregated, placed on and covered by plastic sheeting, and characterized to aid in evaluating and documenting contractor-proposed handling, re-use, or disposal. Contractor proposed handling, re-use, or disposal of waste materials should be conducted in accordance with local material management jurisdictions and/or receiving facility criteria. Confirm inclusion of this measure on all applicable plans and confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department, Caltrans, and Contractor INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 96 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party Noise NOI/mm-1 Construction activities shall be limited to the daytime hours of 7:00 a.m. to 10:00 p.m. Monday through Friday, and 8:00 a.m. to 5:00 p.m. on Saturday or Sunday, consistent with City of Arroyo Grande construction noise exception standards. Confirm inclusion of this measure on all applicable plans and confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department, Caltrans, and Contractor NOI/mm-2 All equipment will have sound-control devices that are no less effective than those provided on the original equipment. No equipment will have an unmuffled exhaust. Confirm inclusion of this measure on all applicable plans and confirm compliance with this measure through site verification. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department, Caltrans, and Contractor Recreation REC/mm-1 Construction activities shall be scheduled and conducted to minimize closure of Kiwanis Park to the greatest extent possible. Kiwanis Park will only be closed when necessary for contractor access, and will remain open to the public through the duration of construction activities. All park recreational features affected by construction, such as picnic benches, will be relocated or replaced outside of the construction limits; these features will be available for use in adjacent areas during the duration of construction activities. Access to the park will be temporarily relocated from the west to the east side of the park during any closure. The City of Arroyo Grande Public Works Department will designate several parking places for park use and avoid construction activities that would impact access to these spaces. A detour along Traffic Way will be signed throughout the duration of construction activities to allow bicyclists continued access to their desired destination. Confirm inclusion of this measure on all applicable plans and confirm compliance with this measure through site verification. The City of Arroyo Grande Public Works Department will confirm that alternative parking places have been designated. Prior to initiation of project construction and throughout the duration of construction activities City of Arroyo Grande Public Works Department, Caltrans, and Contractor INITIAL STUDY MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 97 of 100 Mitigation Measure Requirements of Measure Compliance Method Verification Timing Responsible Party Transportation/Traffic TT/mm-1 Prior to any road closures, the City of Arroyo Grande shall provide notice to all residents, business owners, and public facilities within 500 feet of the proposed project. The notice shall include the following information: dates of construction, temporary road closures and detours, removal of parking spaces, and contact information including the phone and email address of the City staff person responsible for responding to and addressing public complaints regarding noise, air emissions, and any other issues. The notice shall be provided at least 2 weeks prior to any planned road closure. In addition, the notice shall be posted on the City’s website and Facebook page. The City of Arroyo Grande shall provide notice to all residents, business owners, and public facilities within 500 feet of the proposed project. Prior to any road closures City of Arroyo Grande Public Works Department INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 98 of 100 7. References California Department of Conservation (CDOC). 2010. San Luis Obispo County Williamson Act FY 2009/2010. Available at: ftp://ftp.consrv.ca.gov/pub/dlrp/wa/SanLuisObispo_09_10_WA.pdf. Accessed January 30, 2017. ————. 2014. Farmland Mapping and Monitoring Program, San Luis Obispo County Important Farmland 2014. California Department of Conservation, Division of Land Resource Protection. California Department of Resources Recycling and Recovery (CalRecycle). 2017. Facility/Site Summary Details: Cold Canyon Landfill, Inc. (40-AA-0004). Available at: http://www.calrecycle.ca.gov/SWFacilities/Directory/40-AA-0004/Detail/. Accessed July 2017. California Department of Transportation (Caltrans). 2017. California Scenic Highway Mapping System. Available at: http://www.dot.ca.gov/hq/LandArch/16_livability/scenic_highways/. Accessed January 23, 2017. City of Arroyo Grande. 2001a. General Plan Update – Circulation Element. City of Arroyo Grande, California. ————. 2001b. General Plan Update – Land Use Element. City of Arroyo Grande, California. ————. 2001c. General Plan Update – Parks and Recreation Element. City of Arroyo Grande, California. ————. 2001d. General Plan Update – Safety Element. City of Arroyo Grande, California. ————. 2007. General Plan Update – Agriculture, Conservation and Open Space Element. City of Arroyo Grande, California. Amended June 12, 2007. ————. 2009. Land Use Map. City of Arroyo Grande, Community Development Department. ————. 2010. Zoning Map. City of Arroyo Grande, Community Development Department. ————. 2012. General Plan Update – Economic Development Element. City of Arroyo Grande, California. Adopted on October 9, 2012. ————. 2013. City of Arroyo Grande Climate Action Plan. City of Arroyo Grande, California. Adopted on November 26, 2013. ————. 2016. General Plan Update – Housing Element. City of Arroyo Grande, California. Adopted March 2016. ————. 2017a. Arroyo Grande City Parks. Available at: http://www.arroyogrande.org/164/City-Parks. Accessed June 2, 2017. ————. 2017b. Arroyo Grande, California Municipal Code. Available at: http://library.municode.com/index.aspx?clientId=16194&stateId=5&stateName=California. Accessed June 2, 2017. City of Arroyo Grande and Graves, Catherine. 2003. Design Guidelines and Standards for the Historic Character Overlay District (D-2.4). City of Arroyo Grande, California. INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 99 of 100 Earth Systems Pacific. 2004. Conceptual Soils Engineering Report, Bridge Street Bridge. Prepared for the City of Arroyo Grande Federal Emergency Management Agency (FEMA). 2012. Flood Insurance Rate Map Number 06079C1602G. Map revised: November 16, 2012. Available at: https://msc.fema.gov/portal/search?AddressQuery=- 120.578749%2C%2035.122674#searchresultsanchor. Accessed July 2017. Federal Transit Administration (FTA). 2006. Transit Noise and Vibration Impact Assessment. FTA-VA-90- 1003-06. May 2006. Available at: https://www.transit.dot.gov/sites/fta.dot.gov/files/docs/FTA_Noise_and_Vibration_Manual.pdf . Accessed in July 2017. Fugro Consultants. 2013. Phase I Initial Site Assessment (ISA) Prepared for the Bridge Street Bridge Rehabilitation Project. Hall, C.A. 1973. Geology of the Arroyo Grande 15’ quadrangle, San Luis Obispo County, California. Published by the California Division of Mines and Geology in 1973. Available at: https://ngmdb.usgs.gov/Prodesc/proddesc_287.htm. Accessed July 2017. JRP Historical Consulting, LLC. 2015. Historical Resources Evaluation Report, Bridge Street Bridge (49C0196) Project. Prepared for the City of Arroyo Grande. December 2015. ————. 2017a. Findings of No Adverse Effect (FONAE) with Standard Conditions-SOIS for Bridge Street Bridge Project. Prepared for the California Department of Transportation. February 2017. ————. 2017b. Historic Property Survey Report, Bridge Street Bridge Project. Prepared for the California Department of Transportation. February 2017. National Oceanic and Atmospheric Administration National Marine Fisheries Service (NOAA Fisheries). 2011. Southern California Steelhead Recovery Plan. Southwest Region, Protected Resources Division, Long Beach, California. January 2012. San Luis Obispo Council of Governments. 2015. SLOCOG 2014 Regional Transportation Plan/Sustainable Communities Strategy. April 2015. San Luis Obispo County Air Pollution Control District (APCD). 2012. CEQA Air Quality Handbook – A Guide for Assessing the Air Quality Impacts for Projects Subject to CEQA Review. April 2012. Available at: http://www.slocleanair.org/images/cms/upload/files/CEQA_Handbook_2012_v1.pdf. Accessed January 30, 2017. ————. 2017. Naturally Occurring Asbestos (NOA) Map. Available at: http://www.slocleanair.org/rules-regulations/asbestos/noa . Accessed January 30, 2017. SWCA Environmental Consultants (SWCA). 2016a. Bridge Street Bridge Project Archaeological Survey Report. Prepared for the California Department of Transportation and City of Arroyo Grande. January 2016. ————. 2016b. Bridge Street Bridge Replacement or Rehabilitation Project Noise Study. Prepared for the California Department of Transportation. May 2016. INITIAL STUDY / MITIGATED NEGATIVE DECLARATION July 2017 Bridge Street Bridge Rehabilitation Project Page 100 of 100 ————. 2016c. Bridge Street Bridge Replacement Water Quality Assessment Memorandum. Prepared for the California Department of Transportation. May 2016. ————. 2017a. Bridge Street Bridge Replacement or Rehabilitation Project Natural Environmental Study. Prepared for the California Department of Transportation. February 2017. ————. 2017b. Bridge Street Bridge Replacement or Rehabilitation Project Wetlands and Waters Assessment. Prepared for the City of Arroyo Grande and Quincy Engineering, Inc. January 2017. United States Census Bureau. 2011. 2010 Census Summary File 1, Arroyo Grande, California. Available at: http://factfinder2.census.gov/faces/nav/jsf/pages/searchresults.xhtml. Accessed June 2, 2017. U.S. Department of Agriculture Natural Resources Conservation Service (NRCS). Web Soil Survey. Available at: https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm. Accessed December 2016. FINAL Project Report Bridge Street at Arroyo Grande Creek Bridge Existing Bridge No. 49C-0196 Bridge Replacement or Rehabilitation Project Federal Project No. BRLO-5199(027) Prepared For: City of Arroyo Grande Community Development Department Prepared By: December 2015 Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Prepared by: __________________________________ Greg Young, Project Engineer Submitted by 12/29/2015 (916) 368-9181 Mark Reno, Project Manager Quincy Engineering, Inc. Date Telephone Approved by Matt Horn City of Arroyo Grande Date Greg Young C67707 6/30/17 Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project TABLE OF CONTENTS 1. INTRODUCTION .................................................................................................................................. 1 2. EXISTING FACILITY .......................................................................................................................... 2 3. PROJECT HISTORY ............................................................................................................................ 3 4. HISTORICAL BRIDGE CONSIDERATION..................................................................................... 4 5. PUBLIC OUTREACH AND PUBLIC SUPPORT .............................................................................. 5 6. DESIGN AND CONSTRUCTION DATA ........................................................................................... 6 DESIGN CRITERIA ................................................................................................................................................................... 6 BRIDGE WIDTH ....................................................................................................................................................................... 6 BRIDGE RAILING ..................................................................................................................................................................... 7 BRIDGE PEDESTRIAN RAILING .............................................................................................................................................. 8 DESIGN SPEED ......................................................................................................................................................................... 8 DESIGN EXCEPTIONS .............................................................................................................................................................. 8 HYDRAULIC CLEARANCES .................................................................................................................................................... 9 TRAFFIC CONTROL/DETOUR ................................................................................................................................................. 9 RIGHT-OF-WAY ....................................................................................................................................................................... 9 SCHEDULE ............................................................................................................................................................................... 9 AESTHETIC REQUIREMENTS .................................................................................................................................................. 9 DRAINAGE ............................................................................................................................................................................. 10 UTILITIES ............................................................................................................................................................................... 10 GEOTECHNICAL/FOUNDATIONS .......................................................................................................................................... 11 SEISMIC .................................................................................................................................................................................. 11 TEMPERATURE ...................................................................................................................................................................... 11 DECK PROTECTION/CORROSION ......................................................................................................................................... 12 7. ENVIRONMENTAL CONSIDERATIONS ...................................................................................... 12 BRIDGE STREET PERMANENT IMPACTS ............................................................................................................................. 13 BRIDGE STREET TEMPORARY IMPACTS ............................................................................................................................. 13 PUBLIC TRAFFIC CIRCULATION, PARKING AND BUSINESS IMPACTS ............................................................................. 13 SOUTH COUNTY HISTORICAL SOCIETY BUILDING ........................................................................................................... 14 KIWANIS PARK IMPACTS ..................................................................................................................................................... 14 BIKE PATH IMPACTS ............................................................................................................................................................. 14 FALSEWORK .......................................................................................................................................................................... 15 CONSTRUCTION EQUIPMENT ............................................................................................................................................... 15 8. ROADWAY ALIGNMENT ALTERNATIVES ................................................................................ 16 HORIZONTAL ALIGNMENT ................................................................................................................................................... 16 VERTICAL ALIGNMENT ........................................................................................................................................................ 16 STAGED BRIDGE CONSTRUCTION OR ROADWAY DETOUR .............................................................................................. 16 NO BUILD ............................................................................................................................................................................... 16 9. STRUCTURE ALTERNATIVES ....................................................................................................... 17 BRIDGE REHABILITATION (PREVIOUSLY ALTERNATIVE 4B) .......................................................................................... 17 BRIDGE REPLACEMENT (PREVIOUSLY ALTERNATIVE 2) ................................................................................................. 18 10. CONSTRUCTION COSTS ................................................................................................................. 20 11. CONCLUSIONS ................................................................................................................................... 20 APPENDIX ...................................................................................................................................................... 1 APPENDIX A - TITLE SHEET, TYPICAL SECTION, LAYOUT AND PROFILE ......................................................................... 1 APPENDIX B - BRIDGE GENERAL PLAN DRAWINGS ........................................................................................................... 2 APPENDIX C - BASIS OF DESIGN ........................................................................................................................................... 3 APPENDIX D - CONSTRUCTION ESTIMATES ......................................................................................................................... 4 APPENDIX E - PRELIMINARY GEOTECHNICAL DATA ......................................................................................................... 5 APPENDIX F - PRELIMINARY HYDRAULICS DATA .............................................................................................................. 6 Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 1 1. Introduction The City of Arroyo Grande (City) is proposing to rehabilitate or replace the existing historic Arroyo Grande Creek Bridge 49C-0196 in order to increase or remove the 3 Ton load posting on the existing structure. The project will also improve public safety, and reduce future maintenance cost. Bridge Street follows a north-south corridor approximately 0.2 miles east of State Route 101 in the City of Arroyo Grande. Based on the latest Caltrans Bridge Inspection Report (2013), the existing bridge has a Sufficiency Rating (SR) of 12.8, an HS20 Inventory Rating of 0.0 metric tons, and is classified as Structurally Deficient (SD) due to a poor deck condition. The bridge is also considered Functionally Obsolete (FO) due to the narrow deck width and low load carrying capacity. The surrounding land is generally level and is composed primarily of an urbanized business district. The existing bridge is structurally deficient and was posted for only 3 Tons in 1985. This is the lowest posting allowed before bridge closure is required. The project need is to provide a new or rehabilitated bridge that will increase the load carrying capacity and also improve public safety. If the bridge is not rehabilitated or replaced, the condition will continue to deteriorate and eventfully bridge closure will be required. Due to the historic bridge classification and high rehabilitation costs in conjunction with strong public support for the rehabilitation alternative, Caltrans has approved consideration of two preferred alternatives (one preferred replacement and one preferred rehabilitation) in the environmental document. The proposed alternative will rehabilitate or replace the bridge on the existing alignment. As a result, road closure is proposed during the construction phase. Depending on the alternative selected, road closure may be required for up to 8 months. The Federal Highway Bridge Program (HBP) is providing 88.53% of the project funding with the remaining 11.47% funded by toll credits. The total construction cost (including construction engineering) for the project is currently programmed to be $4,820,200. The programmed amount and the construction schedule will need to be updated once the environmental process confirms the preferred alternative. This Project Report summarizes preliminary engineering alternatives considered, and includes site-specific data such as topographic surveys, preliminary geology, hydraulic, and environmental information. This Project Report will also define the project criteria and address project specific issues that must be considered during final design. Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 2 Supplemental Carrier Truss Creek View 2. Existing Facility Bridge Street is classified as an off-system local urban road. The existing bridge is a hybrid structure comprised of an original Pratt pony through truss which is now supported by a supplemental steel deck truss. The structure also has a single southern approach span consisting of a reinforced concrete deck supported by steel stingers. The main truss span is approximately 100 feet long and the approach span is approximately 24 feet long. Two seat type abutments and a single pier supports the northern end of the approach span and southern end of the main truss. The pier consists of one approximately 4'-0" diameter reinforced concrete pile extensions under each truss bearing which are joined together by a reinforced concrete closure wall. The original 24 feet wide pony truss was built in 1908 and carries two traffic lanes with pedestrian sidewalks cantilevered on both sides outside of the truss members. In 1914, a large flow event in Arroyo Grande Creek washed out the southern approach embankment. The existing southern abutment was left in the channel and now serves as the intermediate pier. A new steel stringer approach span and concrete abutment were constructed on the newly formed southern embankment. The sidewalks are composed of timber orientated transversely and supported on steel brackets attached to the truss and approach span stringers. This original bridge structure was first inspected in 1939 and was load posted at that time under order of the Director of the State Department of Transportation for 10 tons per vehicle and 17 tons per semi-truck combination. Bridge inspection records indicate that portions of the approach span deck failed in 1970 causing a temporary closure of the bridge while the reinforced concrete deck was in the first span was replaced. The load posting for the structure was then reduced to 5 tons for all vehicles. A further inspection in 1985 revealed a failed truss diagonal member which resulted in load posting of 3 tons. In 1989, a vehicle collided with vertical latticed truss post and severely damaged it. Upon investigation of the bridge condition after this crash, severe corrosion of the bridges cross beams were discovered and the bridge was closed to all traffic. The City Council then elected to repair the bridge through design and installation of a supplemental steel deck truss (carrier truss) installed underneath the original pony truss which allowed for legal loads of 20T-23T-25T. Unfortunately, during final design of this structural strengthening system, it was discovered that the concrete comprising the bridge abutments Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 3 Reduced Bearing Capacity under the exterior approach stringer was of poor quality and relatively low strength. At that time, the City elected to defer further repairs to the bridge until a later date. In 1997, Caltrans completed a supplemental inspection and determined that a portion of the concrete supporting the exterior stringer for the approach span had been removed in order to install the supporting carrier truss. This pier modification resulted in an unsupported cantilever section which reduced the bearing capacity under the exterior stringer. This condition is the primary reason the bridge has remained posted for 3 tons per vehicle. It is important to note that no previous studies have evaluated the existing bridge for seismic or scour deficiencies. As-built plans of the substructure can't be found so this analysis is not possible. 3. PROJECT HISTORY In 1996, the Arroyo Grande City Council approved a resolution that directed staff to submit a Request for Authorization to Caltrans for preliminary engineering and field review for bridge deck rehabilitation under the Federal Highway Bridge Replacement and Rehabilitation Program (HBRR) now know as the Highway Bridge Program (HBP). This Request for Authorization was officially submitted to Caltrans District 5 Local Assistance in September of that year. At the time, Caltrans indicated that a replacement bridge would likely be more cost effective than a rehabilitation project. The City has always expressed a strong desire to preserve the historic features of the unique bridge. Through a series of conversations, Caltrans concluded there was not enough sufficient information to fund rehabilitation instead of a replacement and directed the City to perform a detailed study to identify all of the existing structural deficiencies and perform a more detailed cost estimate to evaluate bridge replacement versus bridge rehabilitation. In 1999, this analysis was completed by a consultant engineer retained by the City. As part of this study, the City also contracted with a geotechnical engineer to perform field exploration and provide preliminary recommendations on a replacement foundation system. Several alternatives were considered at that time as part of the study. These alternatives included: Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 4 · A No Build alternative, or “Do Nothing” · Upgrade bridge to support vertical loads only · Upgrade bridge to support vertical and lateral (seismic) loads · Upgrade bridge to support vertical and lateral (seismic) loads and widen to meet current geometric standards · Replace existing bridge with a new structure; either with or without historic features of the existing bridge At the completion of this study, the preferred alternative was to upgrade the existing bridge for vertical and lateral loads, but not widen to meet geometric standards. Upon reviewing these findings, Caltrans took exceptions with assumptions made in both the analysis and costs estimates. Among the comments made by Caltrans the following key issues were raised that could affect the projects rehabilitation funding eligibility: · Vertical loads considered for rehabilitation were too low; not up to AASHTO standards · Required seismic rehabilitation work may have been under scoped, and therefore; under estimated in costs · Lifecycle costs of the bridge rehabilitation project may have been underestimated · Lifecycle costs of the bridge replacement project may have been overestimated Through the process of comment resolution and additional discussions a consensus on a revised preferred alternative was developed and presented in October of 2005. It was agreed that the preferred project alternative would be to replace the existing bridge with a new structure that incorporated the historic features of the existing bridge. In May of 2012 the City entered into a contract with Quincy Engineering (QEI) to obtain environmental approvals and complete the final bridge PS&E. Significant public outreach throughout the preliminary engineering phase has again identified a strong desire from project stakeholders for a rehabilitation alternative. Caltrans and the City Council have agreed to support development of preliminary engineering for both a preferred bridge replacement alternative and a preferred bridge rehabilitation alternative. The outcome of the environmental process for historical bridges will ultimately determine what alternative is selected. 4. HISTORICAL BRIDGE CONSIDERATION In the 1980s, the Bridge Street Bridge was determined to be eligible for listing in the National Register of Historic Places and Registry of Historic Truss Bridges in California. This eligibility is due to the fact that this bridge is one of the best examples in California of a “classic” pony truss and is classified as a Category 2 bridge. Based on its National Register eligibility, the bridge is considered a historic property for the purposes of NEPA Section 106 compliance and also as a historical resource for CEQA compliance. The City of Arroyo Grande and local residents have long appreciated the historic and cultural value of this bridge. Since there are nearby bridges that provide access over Arroyo Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 5 Grande Creek without significantly disrupting traffic patterns, the City has elected to leave this historical bridge in place with the posted load restrictions and nonstandard traffic widths. Unfortunately, future bridge maintenance as the bridge deteriorates may become a large financial obligation for the City and due to the need for proper traffic circulation; permanent road closure is not an option. Not only is the existing bridge Structurally Deficient to carry vehicular live loads but also has significant seismic deficiencies as well as possible foundation settlement and tilting. Currently, the City has an opportunity to utilize federal funding through the Highway Bridge Program to rehabilitate or replace this bridge while maintaining some of the original truss members. This would increase functionality of the bridge to carry standard traffic loads, increase public safety by reducing risks from a seismic event, and help sustain the historic aesthetics of a key historic feature in the City. As mentioned previously, the environmental process for historical bridges will ultimately stipulate what bridge alternative will be eligible for federal funds. 5. PUBLIC OUTREACH AND PUBLIC SUPPORT To assure success of the project and to meet the goals of civic leaders and the community, a balance must be achieved between the desire to maintain a historically significant bridge and the need to bring the bridge up to current loading specifications. A well planned public outreach program will be critical to finding that balance. The City continues to employ traditional and innovative outreach methods to obtain key community concerns, consensus, and buy-in with outcomes that are technically and politically feasible. The project team has identified the following entities as some of the key stakeholders whose participation and buy-off during the project development are important for project success: · City of Arroyo Grande Community Development and, Public Works Departments · City of Arroyo Grande Planning Commission · Architectural Review Committee · Chamber of Commerce · City of Arroyo Grande Historical Resources Committee (HRC). The HRC makes recommendations to the Architectural Review Committee, Planning Commission and/or Community Development Director regarding the administration of the provisions of Title 16 of the Municipal Code by preparing, reviewing, and recommending historical preservation criteria, standards, and guidelines. · Arroyo Grande Village Improvement Association (VIA) including Bridge Street Business Owners. The VIA is an association of downtown businesses dedicated to the preservation, restoration and promotion of downtown core. One of the Board of Directors is also involved with the South County Historical Society. · South County Historical Society (SCHS). The SCHS is a non-profit organization committed to preserving south San Luis Obispo County’s rich history. The SCHS is located adjacent to Bridge Street Bridge and have expressed interest in participating in the project development process. Community outreach completed to date is summarized on the City website. Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 6 6. DESIGN and CONSTRUCTION DATA Establishing the correct design criteria is key because it has a profound impact on engineering and construction cost during final design. Our Team has developed a “design critieria memorandum” and a “basis of design” document (located in Appendix B) to obtain agreement on all controlling criteria as early as possible in the project development process. The process of developing this document also served as a mechanism for incorporating input from the both the City and Caltrans as part of building consensus for the project alternatives. QEI has made recommendations for all controlling design standards (City and AASHTO) and provided it to the City for review and approval. The reasoning behind some of the decisions made is documented below: Design Criteria All alternatives must meet the following criteria: · Bridge Replacement Design AASHTO Bridge Design Specifications 6th Edition with Caltrans Amendments dated January 2014. The proposed structure will be designed for HL93, permit, and tandem truck live loading, and satisfy the current Seismic Design Criteria (SDC) Version 1.7. · Roadway Design The roadway standards will be based on AASHTO – “A Policy on Geometric Design of Highways and Streets”, 2011 6th Edition (Green Book). Bridge Width The total existing bridge width is 37’-6”. This is comprised of two 12’-0” lanes with no shoulders between the truss elements and two 5’-0” sidewalks outside of the truss elements. The truss elements are each 1’-3” wide. The existing bridge also has 6” wide pedestrian railings outside of the sidewalks but does not have any vehicle railings. As part of this project, traffic counts were collected by Metro Traffic Data Inc. at this site and averaged 3336 vehicles per day between October 18th and October 24th 2013. The roadway width based on AASHTO standards would consist of 12 foot lanes with 3 foot shoulders (standard geometrics based on roadway classification and ADT). Based on conversations with City staff and feedback from numerous public outreach forums, it became apparent that the proposed bridge width was a key evaluation criterion for any rehabilitation or replacement alternative. In order to fully assess what bridge width provides the best compromise between functionality, strength, and program requirements, several width and lane configurations were analyzed in the Rehabilitation and Replacement Strategy Report. After presenting the study findings, the City has selected a two lane 28 foot wide clear width for the replacement alternative, and a two lane 24 foot clear width for the rehabilitation alternative in order to match the existing condition. Both alternatives will require a design exception because they are below the standard 30' clear width. Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 7 In summary the bridge replacement alternative will consist of two 12’ lanes with 2’ shoulders for a 28’ wide clear width. A 1’-6” wide railing will be installed between traffic and the truss elements. The original truss elements will then be mounted outside the vehicle railing with 5 foot wide sidewalks cantilevered outside the truss elements. The total width for the replacement alternative is approximately 46'. The bridge rehabilitation alternative will match the existing condition and have two 12’ lanes with no shoulders. The clear distance between the truss elements will be approximately 3’-0” wider than the existing condition in order to accommodate 1’-6” wide vehicle railings. Similar to the existing condition, a 5 foot wide sidewalk will be cantilevered outside the truss elements. The total width for the rehabilitation alternative is approximately 40'-6" The roadway structural section will conform to the City standard of 0.38’ HMA over 0.67’ AB over 1.0’ of Sub-base which is based on a TI of 7. QEI will confirm that this structural section will be adequate after the R value is obtained from the geotechnical test borings. Bridge Railing The existing bridge relies on the through truss elements to serve as a vehicular railing. For local agency projects to qualify for federal funding, Caltrans Structures Local Assistance has indicated that vehicular bridge railings must conform to the full-scale crash-test criteria established in the AASHTO Manual for Assessing Safety Hardware (MASH). MASH is the new state of the practice for the crash testing of safety hardware devices for use on the National Highway System (NHS). It updates and replaces NCHRP Report 350. Quincy recommends that the selected alternative utilize a vehicular railing inside of the truss elements to protect vehicles from impacting the blunt end of the fixed historic chords. This approach would prevent future accidents similar to the 1989 incident where a vehicle collided with the vertical latticed truss post and severely damaged it. The public and the City would like to minimize the size and appearance of this internal barrier as it has the potential to visually impact the existing historic truss. Consequently Quincy has proposed, and the City has concurred, that the "Washington DC Historic Bridge Railing" will be used. The bridge rail will be a 27” tall 1’-6” wide An additional challenge will be handling the “end treatments” on the bridge approaches. End treatments will need to consider an appropriate level of crash protection while not detracting from the historic project context. A tapered end approach or wrapping the railing around the curb return on the approach side is proposed to eliminate the need for unsightly crash cushions. Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 8 Bridge Pedestrian Railing Both alternatives will reuse the existing cantilever sidewalk and hand railing. Three modifications to the existing railing will be required. First the existing timber planks will be replaced with new wooden planks. The spacing of the new planks will be closer than the existing to satisfy ADA requirements. The existing railing also has 11 ½” square openings which exceed the AASHTO 6” maximum opening requirements. An additional 1 ½” x ¼” thick steel bar or cables will be attached midway between the existing lattice bars to reduce the opening size below 6”. This bar matches will match the existing size, shape and color of the existing railing. Last current standards require a safety toe rail or curb. An additional piece of steel will be attached to the existing steel posts near the top of timber planks. This steel will be painted green and act as a safety toe rail. All other portions of the railing will remain unchanged. Design Speed The design speed for this project will be 30 mph based on AASHTO standards. This design speed is appropriate for the Central Business District and is also consistent with the design speeds of the adjacent roadways. Design Exceptions One design exception is proposed for this project. Additional justification regarding design exceptions will be documented in final design with a design exception fact sheet. Shoulder Width Typical standards for this level of ADT would require 3 foot shoulders. The City has requested a design exception for this condition, and proposes 2 foot shoulders for the replacement alternative and no shoulders for the rehabilitation alternative. Justifications for this design exception include: · Matches or improves the existing width condition · Lower accident history · Sidewalks are proposed so pedestrians will not be using the shoulders · Bridge railing will be added which will improve safety over the existing condition · Lower design speed Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 9 Hydraulic Clearances Hydraulic Design Criteria established in Caltrans Local Assistance Procedures Manual dictates that a facility be capable of conveying the base or 100-year flood (Q100) and pass the 50-year flood (Q50) “…without causing objectionable backwater, excessive flow velocities or encroaching on through traffic lanes.” The same criteria also recommend a minimum freeboard clearance of 2 feet above the 50-year floodwater surface elevation (WSE50) to provide clearance for drift. Both project alternatives will be designed to meet this criteria. Traffic Control/Detour Since the bridge will be rehabilitated or replaced on the existing alignment, and there are viable detours utilizing Traffic Way or Mason Street adjacent to the bridge, the road will be closed during construction. Depending on the alternative selected, road closure may be required for up to 8 months during the bridge construction phase. If possible, the closures will be coordinated around the Strawberry and Harvest Festivals in order to minimize impacts to the public. Road closure would eliminate staged construction which will minimize construction time and also reduce construction costs. Right-of-Way The project is located in a developed urban area. From a preliminary review of the applicable parcel maps, it appears that the project is located within 60 feet of City right-of-way centered along the existing road. Since Replacement or Rehabilitated structures will be located on existing alignment, no additional right-of- way acquisitions will be required to construct this project. Research into land titles may be required to determine if additional easements or infrastructure (utility, irrigation, or other encroachments) will be affected by the project during construction, or in the final project configuration. Temporary construction easements will be required in order to provide room for construction and contractor staging areas. Schedule The construction schedule will be dependent on the environmental process and public input associated with the historic bridge. The construction schedule will need to be updated once the environmental process gets underway and the preferred alternative is confirmed through the environmental process. Aesthetic Requirements Aesthetics are usually dictated by the owner of the facility, but can often be heavily influenced by local interest groups. Typically the HBP program will pay for aesthetic elements in the 3%-7% range of the construction costs. Since this project has considerable historical concerns, a higher cost can sometimes be justified. Our team anticipates strong input from both the City and local community regarding the bridge aesthetics and, in particular, how historic features of the existing bridge will be maintained. Thus far the project stakeholders have offered the following input: · Stained or colored concrete in order to allow the bridge to better blend into the surrounding environment. · Stamped deck concrete that looks like timber planks · End treatments to the bridge railing that makes it look similar to the existing historic truss Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 10 Drainage The existing bridge allows roadway drainage to sheet flow directly into the river. Current environmental permit requirements usually stipulate that the storm water on bridges be collected and transported off the bridge into a roadway drainage facility. Both alternatives will be crowned at the roadway centerline and utilize concrete curbs and a longitudinal slope in order to collect the storm water. Eventually the roadway drainage system will empty into the creek. Utilities QEI will lead the overall utility coordination efforts. This process begins with an “A-letter” to identify existing facilities, followed by a “B-letter” to notify owners of conflicts or temporary relocations and finally a “C-letter” which serves as a relocation notification which also identifies time specific relocation requirements. This approach allows for identifying utility conflicts early in the alternative evaluation phase and also incorporation of utility relocation plans into the development of the roadway and bridge improvement designs. Whenever possible, and to avoid right-of-way delays and costs, utility relocations should occur prior to awarding the construction contract. Field observation has identified multiple utilities attached to the bridge. Based on bridge records the utilities present on this bridge are owned by the City and include a 6” ductile iron water supply line and an 8” ductile iron sanitary sewer line that were upgraded in 1997. Utility relocations will be required, at least temporarily during construction, and coordinated with each bridge alternative. The utility relocation process for Federally Funded Projects has been recently revised by Caltrans, requiring additional coordination due to the mandatory Caltrans involvement. As part of this process, a Report of Investigation (ROIs) must be submitted to Caltrans for each effected utility prior to requesting the utility to relocate. The ROI must include the following information and be prepared for each utility requiring modification: · The conflict map or plan; · Relocation plans, either prepared by the utility or the project designer; · Supporting documents from the utility stating liability claims and owner’s estimated cost; · A copy of the proposed Utility Agreement; · A copy of the proposed Notice to Owner (to relocate); and · Franchise Agreements and/or permits for the utility installation (if available). Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 11 Geotechnical/Foundations A preliminary foundation memo has been prepared by Fugro and is included in Appendix E. Fugro’s boring DH-101 was drilled in the north abutment area on July 6, 2015, to a depth of approximately 95 feet below the existing ground surface. The subsurface conditions encountered by Fugro generally consisted of artificial fill overlying alluvium and Paso Robles Formation. Based on these findings, it does not appear that the alluvium soils are strong enough to support a shallow bridge foundation, such as a spread footings. Therefore deep pile foundations will be required. Driven piles were considered, however pile driving generates noise which can disturb adjacent businesses and vibrations that can damage nearby buildings or injure fish. This is a particular concern for this project since there is a historical building less than 75 feet away from a proposed south abutment location. Possible mitigation measures for driven piles could include crack and vibration monitoring during construction, however drilled shafts have been selected to reduce risk and simplify environmental studies. Cast-in-Drilled Hole (CIDH) piles will be utilized to support both alternatives. These foundations would involve drilling holes, and possibly using drilling slurry, temporary casings, and/or permanent casings to reduce the potential for caving. After the holes are drilled, a reinforcing cage will lowered in place, and concrete will be pumped into the hole. Currently 30" diameter piles are proposed at the abutments and a single 60" to 84" diameter pile extension is proposed at the center Pier. Seismic The site response is controlled by deterministic estimates of ground motion occurring on either the San Luis Range fault system or the Los Osos fault. The estimated peak ground acceleration for the bridge site is approximately 0.68g. The site response for periods less than about 0.3 second is controlled by a M6.9 earthquake on the Los Osos fault. The site response for periods greater than about 0.30 seconds is controlled by a M7.1 earthquake on the San Luis Range fault system. The estimated average shear wave velocity for the site is approximately 300 meters per second, characteristic of a Type D soil. Temperature Maximum Temperature: 108° F Minimum Temperature: 23° F Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 12 Deck Protection/Corrosion The project is located approximately 3 miles from the ocean and is therefore considered a non-marine environment. The project is also not located in a mountainous region that is exposed to deicing salts. Therefore special deck protection measures such as increased concrete cover and epoxy coated reinforcement will not be required. Drilling samples will be taken to check for corrosive soils; however corrosive soils are not anticipated at this site. 7. ENVIRONMENTAL CONSIDERATIONS The City will be the lead agency for the CEQA document. If the existing historic bridge is impacted by the project in such a way to be classified as significantly un-immitigable (bridge replacement or extensive rehabilitation that changes the character of the bridge), this impact to an historic property would likely require the CEQA documentation to be a Focused EIR. If the rehabilitation alternative is selected and it is determined that the historic resource is not significantly impacted by the project then the City may choose to pursue an IS/MND CEQA document. Caltrans will be the lead agency for NEPA documentation. It is anticipated that NEPA document will be a Categorical Exclusion (CE) supported by technical studies. The following Technical Studies are required based on the signed PES form and will be prepared to support the environmental documents: · Traffic Study (technical memorandum) · Noise Study (technical memorandum) · Hazardous Materials/ISA · Location Hydraulic Study and Flood Encroachment Report · Natural Environment Study · Biological Assessment (with informal/formal consultation USFWS and NOAA) · Wetland Delineation and Assessment · Programmatic Section 4(f) Evaluation · Visual Resources VIA checklist · Cultural Resources Area of Potential Effects map Historical Properties Survey Report Archaeological Survey Report Historic Resources Evaluation Report Findings of Effect Report (Caltrans, SHPO) Memorandum of Agreement (Caltrans, SHPO, and ACHP) Agency Permitting is anticipated to be required for the following agencies: · United State Army Corps of Engineering 404 · California Department of Fish and Wildlife 1602 Stream Bed Alteration Agreement · Regional Water Quality Control Board 401 Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 13 Bridge Street Permanent Impacts Both the rehabilitation and replacement alternatives would require creek slope excavation, backfill and rock slope protection to protect the abutments and roadway approach. For the rehabilitation alternative there will be permanent impacts in the creek resulting from one or two (5’ to 8’) diameter Cast-In-Drilled Hole concrete pile extensions or a concrete pier wall on a piled footing that will support a cast in place concrete cap. These will be installed near the location of the existing concrete pier that supports the existing bridge (after the existing bridge foundations are removed). There will also be a slightly larger footprint as the rehabilitated bridge will be approximately 40’-6” wide which is 3’-0” wider than the existing bridge to accommodate vehicular bridge railing. The replacement alternative would clear span the creek resulting in no channel supports. This results in less permanent creek impacts relative to the existing condition and the rehabilitation alternative. For replacement alternatives, it will be necessary to remove the functionally obsolete status in order to be eligible for federal replacement funds. A wider 28 foot clear width (plus sidewalks, truss, and railings) will be required to accomplish this. This would require a minimum total bridge width of approximately 46’. This width is approximately 8'-6" wider than the existing. Consequently, the proposed bridge would have permanent impacts due to a wider footprint. Bridge Street Temporary Impacts The proposed project will involve minor modification/alteration to the creek with the placement of a temporary road in the creek in order to allow for contractor access. This access road is necessary to facilitate bridge removal, and place the temporary bridge supports (falsework) to construct a replacement bridge, or install new pile foundations for a bridge rehabilitation alternative. Construction for both alternatives would require clearing of the vegetation below and adjacent to the bridge. Cofferdams, stream diversion and dewatering may also be required to provide a work area for either replacement or rehabilitation alternatives. Following construction, the temporary fill for the access road and diversion will be removed and the creek will be restored to the existing topographic contours. The construction for both alternatives will include removal of the existing bridge superstructure and foundations. The existing bridge concrete deck will be broken up into smaller pieces by excavators mounted with a concrete breaker “hoe-ram” attachment. The concrete debris will fall to a cleared channel work pad below the bridge for later removal offsite. After the deck is removed, cranes will remove sections of the existing truss and steel girder approach spans. Next portions of the supplement truss will also be removed with cranes. Last the existing concrete abutments and piers will be broken into smaller for removal from the site. The existing bridge will be removed 3 to 5 feet below the existing ground line. Both alternatives will require new foundations that till consist of deep piles. Drilled pile foundations would consist of Cast-in-drilled-hole (CIDH) piles. Public Traffic Circulation, Parking and Business Impacts The biggest impacts to the public will be construction noise and the proposed road closure during construction. Depending on the alternative selected, closure could be required for up to 8 months. In addition to road closure, parking spaces adjacent to the bridge will also be taken temporarily in order to provide room for contractor staging. Nine parking places dedicated to Mclintocks and 21st Century in the southwest parcel (adjacent to the Historical Society), and the entire southeast lot of UFCW Local 770 Union Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 14 Hall will need to be closed during construction for contractor staging. After coordination with City staff, it is not feasible to take any parking spaces north of the bridge along Olohan Alley or Klondike Pizza. North of the project Bridge Street will be closed from the southern edge of the Klondike Pizza driveway to the adjacent crosswalk along Olohan Alley. Driveway access and crosswalk access will be maintained, however the south portion of the sidewalk adjacent to Kiwanis Park and a picnic area north east of the bridge will need to be close during construction to allow for contractor staging. South of the project Bridge Street will be closed from the midpoint of the South County Historical Society driveway to the south end of the Union Hall driveway. The entire Union Hall driveway and northern half of the South County Historical Society driveway will be closed during construction. Access to the Historical Society and parking for the Historical Society will be maintained. Pedestrians and vehicles will need to be detoured along Traffic Way or Mason Street during construction. The Detour along Traffic Way via East Branch and Nelson Street is approximately 0.4 miles. The Detour along Mason Street via Olohan Alley and Nelson Street is approximately 0.5 miles. It would be possible to reduce the Detour for pedestrian to approximately 0.35 miles if they use the short street swing bridge or 0.3 miles if access is granted through the Historical Society Parking Lot. South County Historical Society Building The South County Historical Society has been designated as a historic building. The existing access and parking for the Historical Society will be maintained throughout construction. In addition, bridge foundations will consist of drilled piles. Drilled piles minimize or eliminate vibrations relative to driven piles which could have possible caused damage to the building. Since all access will be maintained and drilled foundations will reduce or eliminate vibrations no adverse effects will occur to the existing historic building. Kiwanis Park Impacts Access and temporary use of the park is necessary for the project. The park provides the best access due to gradual slopes and undeveloped area that would not require eliminating northern parking places during construction. The City has agreed that there will be no adverse effect to the park during construction if the following mitigation measures are implemented. The park will only be closed when necessary for contractor access. This will be less than the duration of the total length of the construction project. All park recreational features affected by construction such as picnic benches will be relocated or replaced outside of the construction limits. These features will be available for use during the construction duration. Last, access to the park will be temporarily relocated to the East side of the park. The City will also designate several parking places for park use. The only alternative to avoid park affects completely would be the no build option. Bike Path Impacts Bridge Street is designated as a class III route in the City’s bicycle master plan. This bike route was signed in 2001 as part of the City’s Prop 116 Bikeway One project. The bike route is currently being signed across the bridge, down Olohan Alley to Mason Street and then up to East Branch Street to head east out of town. This does not reflect the City Bike & Trails Master Plan which shows the route along Bridge Street up to East Branch Street. Regardless of the existing or future plans the bike route is signed and is a recreational feature of the City. The City has agreed that there will be no adverse effects to the bike route if the following mitigation measures are implemented. The bike path will only be closed when necessary for bridge construction. This will be less than the duration of the total length of the construction project. A Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 15 detour along Traffic way will be signed which will allow users continued access to their desired destination. The only alternative to avoid bike path affects completely would be the no build option. Falsework Falsework would be required in the creek for the cast-in-place concrete bridge alternative. There are no known environmental restrictions on this project that would preclude the use of falsework in the creek. The allowable time the falsework can remain in the creek may be subject to the California Fish and Wildlife Streambed Alteration Agreement, as well as other permits and environmental mitigation requirements. Construction Equipment Equipment anticipated to be used in the construction of the replacement bridge or the rehabilitation includes excavators, dozers, cranes, dump trucks, concrete trucks, concrete pumps, and pile drilling equipment. Removal of the existing bridge will require excavators, hoe rams, cranes and dump trucks. Construction is anticipated to be completed within one construction season. Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 16 8. ROADWAY ALIGNMENT ALTERNATIVES Horizontal Alignment Due to the limited right of way and extensive development adjacent to the right of way at all four bridge quadrants, a replacement or rehabilitation on the existing alignment is the only feasible roadway alignment. This option will also reduce environmental impacts. The rehabilitation (approximately 40’-6” wide) and the replacement (approximately 46’-0” wide) will both be wider than the 37’-6” wide existing bridge. As a result, horizontal shoulder and sidewalk tapers may be required to conform to the existing sidewalk and curb locations. Vertical Alignment The proposed vertical alignment will conform closely to the existing for either rehabilitation or replacement alternatives. Based on the preliminary hydraulic water surface and existing or proposed structure depth, it will not be necessary to raise the roadway profile. Minor adjustment may be made for replacement alternatives in order to allow for longitudinal bridge drainage. Impacts to adjacent parcels due to grade adjustment are not anticipated. Staged Bridge Construction or Roadway Detour Staged bridge construction was considered but ultimately rejected due to structural feasibility; increased cost relative to non-staged construction and increased construction time. The existing bridge is narrow and derives structural support from supplemental truss elements which are required to remain intact. Staged construction is only feasible when half the structural support system can be removed while the structural integrity for traffic loads are maintained on the adjacent portion. Since the truss elements on each side of the bridge are braced to each other and are not independent support elements such as girders, it is not feasible to maintain the structural integrity during staged construction. Since there is a viable detour utilizing Traffic Way or Mason Street adjacent to the project, road closure and construction along the existing alignment has been selected. No Build This alternative would not satisfy the project’s purpose and need. The existing bridge condition would continue to deteriorate and require costly repairs leading to an eventual closure. This alternative has been rejected due to safety concerns. Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 17 9. STRUCTURE ALTERNATIVES Quincy studied numerous alternatives which were presented in the Rehabilitation and Replacement Strategy Report. Two preferred alternatives have been identified by the City council and other project stakeholders. The preferred alternatives have been presented below. Due to scour and seismic deficiencies, both structure alternatives will require the full replacement of the existing bridge foundations. Therefore both alternatives will require complete bridge removal. Bridge Rehabilitation (Previously Alternative 4B) The preferred alternative with the public and most bridge stakeholders is a rehabilitation of the existing historic bridge. After much analysis and consideration the rehabilitation alternative will consists of replacing the existing supplemental truss with a new higher strength supplemental truss in order to increase live load capacity. A new substructure consisting of cast in place abutments and pier wall along with a new cast in place approach span will also be necessary to upgrade the structure to the latest scour and seismic codes. This alternative will begin similar to the replacement alternative in that all portions of the existing bridge will be removed (the existing historic truss will be salvaged for later reinstallation on the new stronger supplemental truss). After the existing bridge substructure is removed a new substructure will be constructed. The since the existing 100’ long truss length is set, a new pier in the channel will be required near the existing pier location. The existing 25’ long steel girder approach span will also be replaced with a new approximately 39’-0” long steel girder approach span with a new cast in place concrete deck. It is not yet know if the exact steel girders will be reused, however they are not visible from the deck and new steel girders would appear very similar to the existing. These girders may need to get slightly deeper in order to handle the higher live loads. After the new substructure is complete a new supplemental structure will be designed to handle 100% of the current design live loads as well as support the weight of the historic truss. The supplemental structure design would consist of a 3 or 4 truss systems with lateral cross bracings to provide redundancy. The Hydraulic Clearance constraint greatly increased the cost of this alternative. The depth of the new supplemental truss could not be increased so the most efficient way to increase structural capacity is to add additional chord panels. The supplemental truss will be painted brown similar to the existing supplemental truss to reduce the visibility. Since the historic truss will still need to be removed and disassembled during new foundation construction, all the existing lead based paint will be removed and new modern coating which matches the existing color will be applied. Most historic truss members will remain unaltered from the existing condition with the exception of the existing concrete deck and floor beams (floor beams are steel girders that are cast in the concrete deck and connect the two truss elements together, however they are not visible so their loss will not Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 18 change the visual character of the bridge). New floor beams approximately 3’ longer than the existing and a new concrete deck with a curb will be used to connect the truss elements together. Longer floor beams are necessary to widen out the truss element 3 feet in order to install a vehicle railing on both sides of the bridge and still maintain a 24’ wide clear distance for traffic. The total bridge width will be approximately 40’-6”. At this time the existing cantilevered sidewalk members (and railing) will remain unaltered. Should it be necessary to strengthen the sidewalk members for current pedestrian loading, similar shaped members and sizes will be used to reduce changes to the visual appearance. Finally, rivets and pins that are removed as necessary to disassemble the truss will be replaced with rivet bolts and pins that look similar the existing. From the deck level this alternative will look identical to the existing condition with the exception of the truss being approximately 3’-0” wider apart to accommodate a concrete curb with steel vehicle railing (painted green to match the truss). From below the new supplemental truss will not be any deeper, however it will be more substantial than the existing supplemental truss and will contain larger members with more truss elements. The new substructure may also be larger and more substantial than the existing pier wall and abutments, however this will be visually difficult to see from the deck level. Bridge Replacement (Previously Alternative 2) This alternative would replace the existing bridge with an approximately 142’-6” long single span cast-in- place post-tensioned concrete box girder bridge. Portions of the existing bridge, such as the main trusses and railings would then be attached to the new structure as architectural components in order to recreate the historic feel of the existing bridge. Separated and raised wooden sidewalks would be designed to replicate the existing pedestrian sidewalks. This hybrid bridge would therefore marry the structural strength, seismic safety, and reduced maintenance of a modern design with the historic look and feel of the existing historic structure. The bridge would be approximately 46’-0” wide and would consist of two 12’-0” lanes with 2’-0” shoulders. The bridge will also accommodate 5’ sidewalks on both sides with additional width for the existing historical truss elements (each 1’-3” wide). Vehicle railings and a concrete curb (each 1’-6” wide) are also proposed between traffic and the truss elements along with 6” wide outside pedestrian railings. Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 19 Box girders also allow for longer spans at shallower depths relative to other bridge types. This attribute would allow for a replacement bridge to clear span the Arroyo Grande creek without requiring the profile to be raised due to the water surface elevation and bridge depth. A single span configuration would also reduce foundation costs by eliminating the intermediate pier. Clear spanning the creek is desirable because it eliminates supports in the flowing channel which can lead to scour and other costly maintenance issues. Increasing the hydraulic window and removing piers also reduces the risk of debris accumulation on the bridge. Permanent environmental impacts to the creek are also reduced with single span alternatives. Abutment supports could be constructed from the adjacent banks whereas intermediate supports in the channel would require heavy equipment in the creek. Maintenance for concrete structures are minimal relative to other bridge types. The new bridge will also be able to handle full design live load. The bridge would also be striped as a 2 lane bridge with a clear width of 28’ to remove the FO classification. This would still require a design exception for width, however, would improve the existing pinch point at the bridge. Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Page 20 10. CONSTRUCTION COSTS Bridge and Road costs were determined based on preliminary quantities and unit prices. The unit costs shown in the estimates are based on historical cost data for each item in similar construction conditions. The Bridge General Plan and Roadway Construction Estimates are located in Appendix D. These estimates do not include costs associated with right-of-way, environmental mitigation, utility relocation, or construction engineering. A 10% mobilization and 20% contingency are included in the total costs to account for the preliminary nature of the estimates. The City is cautioned that the cost estimates are based upon pay item unit costs for similar projects and actual construction costs may vary. The first dependable detailed estimate will occur after the 65% design is complete. This estimate should be used to program construction funds. 11. CONCLUSIONS The alternatives outlined in this report were developed considering design standards, safety, environmental impacts, right of way impacts, historic architectural elements, pedestrian movement, public opinion and costs. The issues considered reflect attributes important to the City and the stakeholders designated by the City. Based on the results of the previously submitted Rehabilitation and Replacement Strategy report, both the City Council and Caltrans concurred that due to the historic nature of the existing structure, a preferred rehabilitation and preferred replacement alternative should be considered. Quincy will perform additional engineering for the preferred alternatives as necessary to support environmental approvals. Quincy will use design criteria presented within this report as a basis for this engineering. The rehabilitation alternative will consist of replacing the existing supplemental truss with a new stronger supplemental truss. The replacement alternative will utilize a single span cast-in-place, pre-stressed concrete box girder with the existing historic truss mounted to the side. Planning study general plans for both preferred alternatives are located in Appendix B. After the 65% design is completed for both alternatives, detailed cost estimates will be prepared for project programming purposes. Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project APPENDIX Appendix A - Title Sheet, Typical Section, Layout and Profile 30% PLANSCITY OF ARROYO GRANDEDEPARTMENT OF PUBLIC WORKSPROJECT PLANS FOR CONSTRUCTION ONBRIDGE STREET BRIDGE OVER ARROYO GRANDE CREEKIN SAN LUIS OBISPO COUNTYIN ARROYO GRANDEFEDERAL PROJECT # BRLO-5199 (027)LOCATION OF CONSTRUCTIONBRIDGE STREET BRIDGEBr. No. 49C-0196ARROYO GRANDE TYPICAL CROSS SECTIONSXS-130% PLANS"B" LINE"B" LINE LAYOUTL-130% PLANS "B" LINE PROFILE"B" LINE PROFILEPROFILEPS-130% PLANS Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Appendix B - Bridge General Plan Drawings w Q z cc a: CJ 0 > 0 a: a: cc LL 0 > .... -0 w ::c .... a: 0 LL Q w a: cc D. w a: D. BB Abut 1 BB ¢::::::! To West Branch St of slope x DESIGN OVERSIGHT 139'-0":!: Measured Along ~ Bridge Street 100'-0":!: Steel Truss ""' ---""'"---/ ------~OG Tap of slope Exist Historical Steel Truss (to remain) I ELEVATION 1"=10' t lb J I 1'/1/ ,' 6' ' , I...( ~ Bridge Street S33°12'00"E I I I PLAN 1"=10' 39'-0":!: Steel Girder I l~I I::",.. 7 Pier 2 I I I I I,,,-, I \ / I '"'-I I I I I EB I ) / 1: ~/ I I "' I "' ;~~~"' 1 Abut 3 Exist 1 '-3" wide Historical Steel Truss 1 '-6" Rail 12'-0" Lane 40'-6" :!: 12'-0" Lane Bridge Street DIST, COUNTY ROUTE 05 SLO rilQUINCV llliilllll ENGINEERING CITY OF ARROYO GRANDE 300 East Broch Street Arroyo Grande, CA 93420 5'-0":!: I• •I Sidewalk I I POST lllLES TOTAL PROJECT (to remain) railing 11 PG m iib::c::-:J !1-'----------1'------L...-...J Exist Sidewalk fa ==~ (to remain) _,/ .1--...... ~~~~~~~ ...... ~~~~~~~ ...... --1 New intermediate support ·' N ·' N New Supp I ementa I Steel Truss TYPICAL SECTION 1 "=5' Rehabi I itaion Measures: 0 New supplemental truss ~ Clean and paint structural steel ~ Replace existing floor beams ~ Replace existing concrete deck ~ Rehabi I itate existing connections ~ Replace existing approach span New Foundations A II 8 >->-0 _J a. w ::> >- "' ;:; N ' 0 N ' A II Top of slope 0 w >->-0 _J a. BRIDGE REHABILITATION SUPPLEMENTAL TRUSS STRUCTURE w >-< C\ ~~~~~~~~~~~~~~~~~~~~~.-~~~~~~ .... ~~~~~~~~~~~~~~~~~~~~ ...... ~ < PLANNING STUDY 5 DESIGNED BY H. Chou DATE 6/5/2014 1-~~~~~~~~~~~~~~~~~~~~-11~ BRIDGE STREET BRIDGE ~, DATE 6/5/2014 DRAWN BY L. Lopez PROJECT ENG I NEER BRIDGE NO. 49C-0196 FI LE => \ \QESERVER5\Eng i neer i ng\C I i ent\Arroyo Grande\A03-100 Bridge Street\CAD\Br i dge\A031 OOa-CONilRAli<fhNOi~ 00-at ion .dgn w Q z cc a: CJ 0 > 0 a: a: cc LL 0 > .... -0 w ::c .... a: 0 LL Q w a: cc D. w a: D. 11 10+75.00 BVC Elev 113.04 -2.465% BB Datum Elev 75.00 BB 11+24.00 Elev. 112.05 ¢::::::1 To West Branch St 11 3 of slope x DESIGN OVERSIGHT x ADVANCE PLANNING STU>Y SHEET (ENGLISH) (REY. 7/16/10) RIC 11 +75.00 EVC Elev 111.46 1.76% per station 100'VC PROF I LE GRADE No Scale 142'-6" :!: (Measured Along ~ Bridge Street) Top of slope ELEVATION 1"=10' 'I s.."' (j , ~ ,· c:il: 12 -0. 70% EB Abut 2 I J / Existing Structure o 49C-0196 (to be , 6' salvaged and relocated) , ( , s.. "l' ~ Bridge Street S33°12'00"E I I I I PLAN 1"=10' 12 Top of slope FG Top of slope Salva~e Existing Truss, Typ 0 I . N 0 Fair Oak Ave c:::::> . I N ' 0 I . N 1 '-6" Barrier I I• 2'-0" Shldr I 12·-o .. Wood Plank Sidewalk, Typ ~ Salvage Steel Overhang Bracket and Roi I ing, Typ 46'-21/2":!: DIST, COUNTY ROUTE 05 SLO rilQUINCV lliilllll ENGINEERING CITY OF ARROYO GRANDE 300 East Broch Street Arroyo Grande.CA 93420 POST lllLES TOTAL PROJECT "A" Line 1 '-3" Truss ·' 12'-0" Metal Bridge Railing, Typ PG CIP P/S Box Girder 5'-0" :!: 611± TYPICAL SECT ION 1"=5' Notes: G) Paint Bridge Number @ Paint "Bridge Street Bridge" ~ Stucture Approach Type E0(10) ~ Creek water elevation at time of survey _., ____ Existing structure to be removed A II 8 r-r- 0 _J a_ w ::> r- "' ;:; N ' 0 N ' A II 0 w r-r- 0 _J a_ RELOCATE BRIDGE REPLACEMENT TRUSS ON CONCRETE BOX GIRDER w >-< C\ DESIGNED BY H. Chou ~~~~~~~~~~~~~~~~~~~~.-~~~~~~--~~~~~~~~~~~~~~~~~~~ ..... ~ < PLANNING STUDY 5 DATE 712912014 1-~~~~~~~~~~~~~~~~~~~ ..... ~ BRIDGE STREET BRIDGE ~, DRAWN BY L. Lopez DATE 712912014 UNIT: CHECKED BY D. Mossmon PROJECT ENG I NEER DATE 712912014 G. Young BRIDGE NO. 49C-0196 APPROVED DATE SCALE: AS SHOWN PROJECT NUMBER & PHASE: Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Appendix C - Basis of Design Project Number A03-100 Design Criteria Memorandum City of Arroyo Grande – Bridge Street Bridge Replacement Page 1 of 3 Criteria Local Standards City of Arroyo Grande (2004) & Arroyo Grande Bike Plan (2006) Caltrans Standards (HDM 6th Edition) (5/7/12) AASHTO Guidelines (2011) Proposed Standard Action to be Taken/Comments Zoning Historic Character Overlay District (D-2.4) Village Mixed Use (VMU) at the bridge and south Village Downtown Core (VDC) at Olohan Alley and north Connective elements such as walkways, common landscaped areas, building orientation, and unfenced property lines are encouraged. Particular care should be taken to assure convenient pedestrian and bike circulation through all parts of a project and to adjoining properties in the Village Mixed Use district. Class III Bike Route Arroyo Grande Bike Plan (2006) Bridge Street is proposed as an Existing Bike Route… Class III (bikes and cars share same roadway). ADT (Metro Traffic Data Inc) 3,336 (Year 2013) with 1% Truck 3,336 (Year 2013) with 1% Truck 3,336 (Year 2013) with 1% Truck 3,336 (Year 2013) with 1% Truck Street Type/Functional Classification Collector Local Road (per CRS maps) Urban Collector Road Collector (City) Structural Sections TI = 7.0 (Min. 0.38’ HMA over 0.67’ AB over 1.0’ of Sub-base) Based on R value and TI (Section 600) Based on R value and TI Min. section of 0.38’ HMA over 0.67’ AB over 1.0’ of Sub-base Design Speed 30 mph For Local roads HDM defers to AASHTO 30 mph - Based on Section 7.3.2 which specifies 30-60mph range. Lower end of this range is appropriate for Central Business Districts. 30 mph Lane Width 12’ For Local roads HDM defers to AASHTO 12’ (Section 4.3 & Pg. 7-13 & 7-29) 12’ Shoulder Width (Replacement) None. See Bike Lane For Local roads HDM defers to AASHTO 3’ (Table.6-6) footnote b 2’ Design exception required. Shoulder Width (Rehabilitation) None. See Bike Lane For Local roads HDM defers to AASHTO 3’ (Table.6-6) footnote b None, Match Existing Design exception required. Class II Bicycle Lane Width 5’ to Curb Flowline 5’ to Curb Flowline (Pg. 300-20) 5’ to Curb Flowline (Pg. 4.6.13) Not selected Project Number A03-100 Design Criteria Memorandum City of Arroyo Grande – Bridge Street Bridge Replacement Page 2 of 3 Criteria Local Standards City of Arroyo Grande (2004) & Arroyo Grande Bike Plan (2006) Caltrans Standards (HDM 6th Edition) (5/7/12) AASHTO Guidelines (2011) Proposed Standard Action to be Taken/Comments Class I Bicycle Lane Width 10’ 12’ Not selected Minimum Right of Way Width Local <60’ Collector <64’ 10’ from catch point (15 feet when feasible) (304.2) N/A Keep existing, no new right of way TCE only. Governed by existing ROW and buildings. Normal Cross Slope 2% 2% (301.2) 1.5%-2% (p. 5-13) 2% Side Slopes None 4:1 or flatter (304.1) 2:1 or flatter (p. 4-26) 2:1 Side Slope lies behind Vertical Curb & Sidewalk Bridge Front Slope None None None 1.5:1 protected with Rock Slope Protection Maximum Superelevation Rate None 6% Per Table 202.2 4%-6% N/A – Straight alignment Minimum Horizontal Curve Radius 550 feet (Table 203.2) 340’ (Table 3-7) N/A – Straight alignment Pavement Corner Radii Not defined Refer to Local Agency standards (405.8) 25’ (Figure 5-3 on 5-21) Match or exceed existing corner radii Maximum Grade 6% 6% (Table 204.3) 7% to 12% (Pg. 3-119) 5% for ADA Compliance Minimum Corner Sight Distance at Intersections Street/Street – 40’along curb face Collector Street/Dwy – 15’ triangle (SP 104-AG) 385’ feet (Table 405.1A) Not Specified Per City Standard (SP 104-AG) Minimum Stopping Sight Distance 250’ (Table 201.1) 271’ (Table 3-2 assuming a downgrade of 6%) 271’ per AASHTO Clear Zone Width No direction for curbed urban streets. Refers to AASHTO 1.5’ from curb face (Pg. 7-37) 1.5’ from curb face Drainage Design 100-yr Storm contained by Top of Curb Local Standard None Culvert – 100 yr storm Roadway – 25 yr Bridge – 100 yr Project Number A03-100 Design Criteria Memorandum City of Arroyo Grande – Bridge Street Bridge Replacement Page 3 of 3 Criteria Local Standards City of Arroyo Grande (2004) & Arroyo Grande Bike Plan (2006) Caltrans Standards (HDM 6th Edition) (5/7/12) AASHTO Guidelines (2011) Proposed Standard Action to be Taken/Comments Design Turning Vehicle None CA Truck None CA Truck, or meet or exceed existing condition Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Appendix D - Construction Estimates Quincy Engineering, Inc. GENERAL PLAN ESTIMATE Bridge Bridge Street Bridge Br.No.49C-0196 Type New Supplemental Truss District 5 Co.SLO Rte. P.M. Length 140 Width 40 Area 5600 sq.ft. Alternative 4B (24 foot wide)Date 12/28/15 Estimate No.1 Project Includes: structures Quant. Checked by:H. Chou Date Price by: CU / EA Cost Index Contract Items Unit Quantity Price Amount 1 Structure Excavation (Bridge) CY 360 $100.00 $35,967 2 Structure Backfill (Bridge) CY 84 $150.00 $12,600 3 Structural Concrete (Bridge) CY 385 $1,200.00 $462,250 4 Bar Reinforcing Steel (Bridge) LBS 139,902 $1.00 $139,902 5 Joint Seal (MR=1") LF 64 $100.00 $6,400 6 36" CIDH Concrete Piling LF 220 $900.00 $198,000 7 48" CIDH Concrete Piling LF 204 $1,200.00 $244,800 8 60" CIDH Concrete Piling LF 80 $1,500.00 $120,000 9 New Supplemental Truss/SW/Railing LS 1 $1,247,900.00 $1,247,900 10 Bridge Removal LS 1 $147,000.00 $147,000 11 Clean Structural Steel (Existing) LS 1 $36,000.00 $36,000 12 Paint Structural Steel (Existing) LS 1 $60,000.00 $60,000 13 Historic Barrier Rail LF 280 $250.00 $70,000 14 $0 15 $0 16 $0 17 $0 18 $0 19 $0 20 $0 21 $0 22 $0 23 $0 24 $0 25 $0 26 $0 SUBTOTAL $2,780,819 MOBILIZATION (_____ %)10 %)$278,082 SUBTOTAL BRIDGE ITEMS $3,058,901 CONTINGENCIES ( _____ %)20 %)$611,780 BRIDGE TOTAL ( _______/SF)$655.48 /SF )$3,670,681 BRIDGE REMOVAL (Conting. incl.) WORK BY RAILROAD OR UTILITY FORCES GRAND TOTAL $3,670,681 FOR BUDGET PURPOSES - SAY $3,671,000 Comments: Quincy Engineering, Inc. GENERAL PLAN ESTIMATE Bridge Bridge Street Bridge Br.No.49C-0196 Type CIP P/S Box (With Truss)District 5 Co.SLO Rte. P.M. Length 142.5 Width 46.3 Area 6598 sq.ft. Alternative 2 Quantities by:SMc Date 12/28/15 Estimate No.1 Project Includes: structures Quant. Checked by: Date Price by: CU / EA Cost Index Contract Items Unit Quantity Price Amount 1 Structure Excavation (Bridge) CY 359 $100.00 $35,900 2 Structure Backfill (Bridge) CY 81 $150.00 $12,150 3 Structural Concrete (Bridge) CY 526 $1,200.00 $631,200 4 Prestressing Cast-In-Place Concrete LS 1 $60,000.00 $60,000 5 48" Cast-In-Drilled-Hole Concrete Piling LF 478 $1,200.00 $573,600 6 Bar Reinforcing Steel (Bridge) LBS $1.00 $143,122 7 Joint Seal (MR=2") LF 69 $100.00 $6,900 8 Historic Barrier Rail LF 285 $250.00 $71,250 9 Bridge Removal LS 1 $147,000.00 $147,000 10 Clean Structural Steel (Existing) LS 1 $36,000.00 $36,000 11 Paint Structural Steel (Existing) LS 1 $60,000.00 $60,000 12 Reassemble and Attach Truss LS 1 $90,000.00 $90,000 13 Reassemble and Attach Walkway LS 1 $37,500.00 $37,500 14 $0 15 $0 16 $0 17 $0 18 $0 19 $0 20 $0 21 $0 22 $0 23 $0 24 $0 25 $0 26 $0 27 $0 28 $0 SUBTOTAL $1,904,622 MOBILIZATION (_____ %)10 %)$190,462 SUBTOTAL BRIDGE ITEMS $2,095,084 CONTINGENCIES ( _____ %)20 %)$419,017 BRIDGE TOTAL ( _______/SF)$381.05 /SF )$2,514,101 BRIDGE REMOVAL (Conting. incl.) WORK BY RAILROAD OR UTILITY FORCES GRAND TOTAL $2,514,101 FOR BUDGET PURPOSES - SAY $2,515,000 Comments: 143,122 Page 1 of 6 City of Arroyo Grande Bridge Street Bridge Replacment Project PROJECT DESCRIPTION: Proposed Improvement: Limits: Total Project Length is approximately 250 feet Between West Branch Street and Fair Oak Avenue in the City of Arroyo Grande TOTAL ROADWAY ITEMS $320,000 TOTAL STRUCTURE ITEMS $0 SUBTOTAL CONSTRUCTION COSTS $320,000 TOTAL RIGHT OF WAY ITEMS $0 None anticipated TOTAL PROJECT CAPITAL OUTLAY COSTS $320,000 Approved by Project Manager ____________________________ Date ________________ Phone Number __________________________ Bridge Street Bridge - Roadway Cost Estimate Bridge Street Bridge over Arroyo Grande Creek Construct new bridge and approach roadway SUMMARY OF PROJECT COST ESTIMATE Page 2 of 6 City of Arroyo Grande Bridge Street Bridge Replacment Project I. ROADWAY ITEMS Section 1 Earthwork Quantity Unit Unit Price Item Cost Section Cost Roadway Excavation 600 CY $65.00 $39,000.00 Clearing & Grubbing 1 LS $4,000.00 $4,000.00 Develop Water Supply 1 LS $2,000.00 $2,000.00 Subtotal Earthwork $45,000.00 Section 2 Pavement Structural Section HMA (Type A)135 TONS $250.00 $33,750.00 Class 2 Aggregate Base 310 CY $100.00 $31,000.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 Subtotal Pavement Structural Section $64,750.00 Section 3 Drainage Roadside Drainage 1 LS $6,000.00 $6,000.00 $0.00 $0.00 $0.00 $0.00 $0.00 Subtotal Drainage $6,000.00 Page 3 of 6 City of Arroyo Grande Bridge Street Bridge Replacment Project Section 4 Specialty Items Quantity Unit Unit Price Item Cost Section Cost Alternative In-line Terminal System 0 EA $3,200.00 $0.00 Transition Railing (Type WB) 0 EA $4,500.00 $0.00 Prepare SWPPP 1 LS $4,000.00 $4,000.00 Construction Site Management 1 LS $2,500.00 $2,500.00 Temporary Construction BMPs 1 LS $4,000.00 $4,000.00 Minor Concrete (curb and gutter) 18 CY $500.00 $9,000.00 Minor Concrete (sidewalk, ramp and driveway) 28 CY $600.00 $16,800.00 Stamped Concrete (crosswalk) 12 CY $800.00 $9,600.00 $0.00 $0.00 $0.00 Subtotal Specialty Items $45,900.00 Section 5 Traffic Items Pavement Delineation 500 FT $1.50 $750.00 Roadside Signs 6 EA $300.00 $1,800.00 Traffic Control Systems 1 LS $4,000.00 $4,000.00 Transportation Management Plan 1 LS $3,000.00 $3,000.00 Construction Area Signs 1 LS $2,500.00 $2,500.00 $0.00 $0.00 $0.00 $0.00 $0.00 Subtotal Traffic Items $12,050.00 II. ROADSIDE ITEMS Section 6 Planting and Irrigation Replace Planting and Irrigation 1 LS $20,000.00 $20,000.00 $0.00 $0.00 $0.00 $0.00 $0.00 Subtotal Planting and Irrigation Section $20,000.00 Page 4 of 6 City of Arroyo Grande Bridge Street Bridge Replacment Project Section 7 Roadside Management and Safety Section Quantity Unit Unit Price Item Cost Section Cost Erosion Control 1 LS $10,000.00 $10,000.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 $0.00 Subtotal Roadside Management and Safety Section $10,000.00 Section 8 Minor Items $203,700.00 x 10% = (Subtotal Sections 1 thru 7) TOTAL MINOR ITEMS $20,370.00 Section 9 Roadway Mobilization $224,070.00 x 10% = (Subtotal Sections 1 thru 8) TOTAL ROADWAY MOBILIZATION $22,407.00 Section 10 Roadway Additions Supplemental Work $224,070.00 x 10%= $22,407.00 (Subtotal Sections 1 thru 8) Contingencies $224,070.00 x 25% = $56,017.50 (Subtotal Sections 1 thru 6) TOTAL ROADWAY ADDITIONS $78,424.50 TOTAL ROADWAY ITEMS $324,901.50 (Subtotal Sections 1 thru 10) Phone # 916-368-9181 Date: 04/29/13 Phone # 916-368-9181 Date: Estimate Prepared By: Michael Sanchez, Quincy Eng. Estimate Checked By: _____________, Quincy Eng. Page 5 of 6 City of Arroyo Grande Bridge Street Bridge Replacment Project III. STRUCTURES ITEMS Structure Structure Structure (1) (2) (3) Bridge Name Structure Type Width (out to out) - (ft) Span Lengths - (ft) Total Area - (ft2) (Widening area only) Footing Type (pile/spread) Cost Per ft2 $0.00 $0.00 (NOT including 10% mobilization and 25% contingency) Total Cost for Structure $0.00 $0.00 SUBTOTAL STRUCTURES ITEMS $0.00 (Sum of Total Cost for Structures) Bridge Removal $0.00 SUBTOTAL REMOVAL ITEMS $0.00 TOTAL STRUCTURES ITEMS $0.00 (Sum of Structures Items plus Railroad Items) COMMENTS: Phone # Date: NOTE: If appropriate, attach additional pages and backup. Estimate Prepared By: Page 6 of 6 City of Arroyo Grande Bridge Street Bridge Replacment Project IV. RIGHT OF WAY ITEMS ESCALATED VALUE A. Acquisition, including excess lanes, damages to remainder(s) and Goodwill B. Mitigation acquisition & credits C. Project Development Permit Fees D. Utility Relocation (State Share) E. Relocation Assistance F. Clearance/Demolition G. Title and Escrow Fees TOTAL RIGHT OF WAY ITEMS $0.00 Rounded $0.00 Anticipated Date of Right of Way Certification (Date to which Values are Escalated) F. Construction Contract Work Brief Description of Work: _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ Right of Way Branch Cost Estimate for Work* * This dollar amount is to be included in the Roadway and/or Structures Items of Work, as appropriate. Do not include in Right of Way Items. COMMENTS: Phone # Date: NOTE: If appropriate, attach additional pages and backup. Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Appendix E - Preliminary Geotechnical Data A member of the Fugro group of companies with offices throughout the world FUGRO CONSULTANTS, INC. 5855 Capistrano Avenue, Suite C Atascadero, California 93422 Tel: (805) 468-6060 August 11, 2015 Project No. 04.62120100 Project Memorandum To: Mark Reno, Quincy Engineering, Inc. Copies: Greg Young, Scott McCauley and Andy Chou, Quincy Engineering, Inc. From: Gresham D. Eckrich, Gregory Denlinger, Fugro Consultants Subject: Preliminary Pile Tip Elevations and Input Parameters for Lateral Loading Analyses, Bridge Street Bridge Replacement, Arroyo Grande, California INTRODUCTION We prepared this memorandum at the request of Quincy Engineering, Inc. (Quincy) to provide our preliminary interpretation of subsurface conditions and preliminary pile tip elevations for the abutment and center pier piles proposed for the Bridge Street Bridge in Arroyo Grande, California. Based on information provided by Quincy, we understand the current project will consist of either rehabilitating the existing bridge over Arroyo Grande Creek or replacing the existing bridge with a new structure. We anticipate that the vertical profile and centerline for the new bridge will be near the existing site grades at the location of the existing bridge. The abutments and center pier will be supported by cast-in-drilled-hole (CIDH) piles. The preliminary design consists of a single row of 30-inch diameter CIDH piles at the abutments, and a single 60-inch diameter pile extension at the center pier. Estimated scour depths of 0 and 3.9 feet for the north and south abutments, respectively, were provided by Quincy. We understand scour data for the center pier is not yet available. The location of the site relative to nearby streets and landmarks is shown on Plate 1, Vicinity Map. The data presented below were developed on the basis of our recent field exploration effort and existing data presented in the Log of Test Borings (LOTB) prepared by Earth Systems Pacific (ESP) for the bridge site in 2004. We note that our laboratory testing program is ongoing; therefore, the data presented below may be modified following our review and interpretation of laboratory test results. SUBSURFACE CONDITIONS Fugro’s boring DH-101 was drilled in the north abutment area on July 6, 2015, to a depth of approximately 95-1/2 feet below the existing ground surface, corresponding to an approximate elevation (EL.) of EL.17-1/2 feet above mean sea level (MSL). For the ESP (2004) exploration program, boring B-1 extended to about elevation EL. 42 (MSL), and borings B-2 and B-3 extended to about elevation EL. 35 (MSL). The approximate locations of the explorations are shown on Plate 2, Exploration Location Map. It should be noted the cross section indicated on Plate 2 is in progress and is not included as part of this memorandum. Project No. 04.62120100 August 11, 2015 2 The subsurface conditions encountered by Fugro and reported by ESP generally consisted of artificial fill (af) overlying alluvium (Qal) and Paso Robles Formation (Qpr). General descriptions of the alluvium and Paso Robles Formation are provided below. Alluvium The alluvium consisted predominantly of interbedded medium dense to dense silty and clayey sand with varying amounts of gravel and soft to very stiff silt and clay. The alluvial materials were encountered to approximately 38 and 66 feet below the surface of Bridge Street at the north and south abutments, respectively, and approximately 44 feet below the ground surface in ESP (2004) boring B-2. Paso Robles Formation Paso Robles Formation materials were encountered below the alluvial soils at the depths noted above and predominantly consist of dense to very dense sand and gravel deposits. The formational soils were encountered to the maximum depths explored by ESP (2004) of approximately 60 to 75 feet below the surface of the road. In Boring DH-101, Fugro encountered a hard clay unit that could be characterized as a poorly indurated or uncemented claystone. Hall (1973) characterizes the Paso Robles Formation as unconsolidated or poorly consolidated gravel or conglomerate, sandstone, siltstone, and claystone. Although designated as rock because of the formation, the sediments of the Paso Robles Formation are generally uncemented units of stiff to hard cohesive soils and medium dense to very dense granular soils and as a result, are described using soil classification terminology in this memorandum. Groundwater Groundwater was encountered in boring DH-101 at a depth of approximately 40-12 feet corresponding to EL. 71-1/2 (MSL). The ESP (2004) borings encountered groundwater at depths ranging from approximately 21 to 37 feet below the ground surface, corresponding to an elevation range of EL. 73 to EL. 77 (MSL). About 2 feet of water was observed within the creek channel on July 6, 2015. For our preliminary evaluation of axial and lateral capacity, we considered a streambed elevation of El. 77 (MSL), and a groundwater elevation of EL. 85 feet (MSL), assuming about 8 feet of water in the creek. PRELIMINARY PILE TIP ELEVATIONS We evaluated the axial and lateral capacity of 30-inch-diameter CIDH piles at the north and south abutments assuming a footing elevation of approximately EL. 95 feet (MSL) for both abutments. In addition, we evaluated pile diameters ranging from 60- to 84-inches for the CIDH pile at the center pier assuming a pile cap elevation of EL. 90 feet (MSL). Preliminary pile tip elevations for the supports are shown in Tables 1 and 2 below. Axial Capacity In accordance with Caltrans (2014a), Caltrans Amendments (2014b) and the AASHTO Load Resistance Factor Design (LRFD) Bridge Design Specifications (AASHTO, 2012), foundations for bridge abutments and bents/piers should be designed using LRFD methods. Project No. 04.62120100 August 11, 2015 3 The nominal resistance (ultimate geotechnical capacity) of CIDH piles was evaluated using the methods presented in Caltrans Memo to Designers 3-1, dated June 2014, and the computer program SHAFTv6.0 (Ensoft, 2012). The nominal resistance of the pile was estimated based on the frictional resistance of the pile within the alluvium and Paso Robles Formation. End bearing was not considered in the evaluation of nominal resistance and we neglected the frictional resistance of the pile shaft within a distance of one pile diameter from the pile tip in general accordance with AASHTO (2012) recommendations. Material properties below EL. 17- 1/2 were extrapolated and assumed to be similar to the hard clay unit encountered at the bottom of boring DH-101. Our evaluation for axial capacity assumed the center-to-center spacing for the single row of abutment piles will be 3-pile diameters or greater. Therefore, group efficiency factors were not applied in our evaluation. In addition, the axial capacity evaluation did not include an assessment of the Extreme Event Limit State because Quincy has not developed the structural demand for that load case at this time. The granular soils at the site are generally dense to very dense and on a preliminary basis do not appear to be susceptible to liquefaction. Therefore, we have not considered downdrag loads from liquefaction in our preliminary assessment of axial capacity. The preliminary estimated tip elevations provided herein are based on the minimum embedment into the alluvium and Paso Robles Formation needed to achieve the nominal resistance equal to the structural load and resistance factors. It should be noted the preliminary pile tip elevations estimated for the diameters considered in our axial capacity evaluation of the center pier are below the lowest elevation (about EL. 17-1/2 [MSL]) explored at the site. For our evaluation, material properties below EL. 17-1/2 were extrapolated and assumed to be similar to the hard clay unit encountered at the bottom of boring DH-101. We recommend this issue be discussed with the project team and that a supplemental drilling program be considered to obtain geotechnical subsurface data below the pile tip elevation or that an alternative design for the center pier be evaluated to allow for a reduced pile embedment length. Lateral Capacity We evaluated the lateral pile load carrying capacity of the CIDH piles using the computer program LPILE Plus v6.35 (Ensoft, 2012), which uses a soil resistance-pile deflection model (p- y analysis) to estimate pile deflections, moments, and shear forces in the pile. LPILE was used to estimate the horizontal movement, maximum moment, and critical pile length for the pile in response to a range of lateral loads under fixed- and free-head conditions. The critical pile length corresponds to the approximate depth where lengthening the pile does not reduce the pile head deflection under the maximum lateral load considered. The estimated tip elevation for the lateral load was estimated from LPILE as 1.3 times the critical length of the pile. Piles should be designed to tolerate the estimated bending moments and shear forces for the range of lateral loads and deflections being considered. It should be noted that the estimated tip elevations presented below are based on the assumption lateral loading is applied longitudinally. In addition, our evaluations for lateral capacity assumed the center-to-center spacing for the single row of abutment piles will be 4-pile Project No. 04.62120100 August 11, 2015 4 diameters or greater, respectively. Therefore, group efficiency factors were not applied in our evaluation. The lateral pile capacities were estimated for level ground. The granular soils at the site are generally dense to very dense and on a preliminary basis do not appear to be susceptible to liquefaction. Therefore, we have not considered lateral loading from liquefaction in our preliminary assessment of lateral capacity. We considered the preliminary scour depth at the abutments in our evaluation of axial and lateral capacity. However, we did not consider scour in our evaluations at the center pier because scour data at the center pier is not currently available. Table 1. Pile Data Table - Abutments Support Location and Pile Type Pile Cap Elevation (ft) Strength Limit State Design Load [per pile] (kips) Required Nominal Resistance (kips) Estimated Design Tip Elevation1 (ft) Strength Limit Extreme Event Compression Tension Compression Tension North Abutment 30-inch CIDH 95 280 4002 0 --3 0 43 (a) --(b) 3 61 (c) 43 South Abutment 30-inch CIDH 954 280 4002 0 --3 0 33 (a) --(b) 3 55 (c) 33 Notes: 1. Design tip elevations are controlled by: (a) Strength Limit compression, (b) Extreme Event Limit compression (c) lateral load 2. Resistance factor = 0.7 applied to Required Nominal Resistance to equal Design Load 3. Extreme Event Design Loads not yet provided 4. Scour depth at south abutment is 3.9 feet per Quincy (2015) Project No. 04.62120100 August 11, 2015 5 Table 2. Pile Data Table – Center Pier Center Pier CIDH Diameter Pile Cap Elevation (ft) Strength Limit State Design Load [per pile] (kips) Required Nominal Resistance (kips) Estimated Design Tip Elevation1 (ft) Strength Limit Extreme Event Compression Tension Compression Tension 60-inch 902 1,750 2,5003 0 --4 0 -26 (a) (b) 4 36 (c) -26 72-inch 902 1,750 2,5003 0 --4 0 -14 (a) --(b) 4 28 (c) -14 84-inch 902 1,750 2,5003 0 --4 0 -4 (a) --(b) 4 15 (c) -4 Notes: 1. Design tip elevations are controlled by: (a) Strength Limit compression, (b) Extreme Event Limit compression (c) lateral load 2. Scour depth data not yet provided 3. Resistance factor = 0.7 applied to Required Nominal Resistance to equal Design Load 4. Extreme Event Design Loads not yet provided PRELIMINARY LPILE INPUT Table 3 through 5 presented below summarize our interpretation of the thickness, description, and estimated engineering parameters assigned to soil units to characterize the subsurface profile at the abutments and center pier. Our interpretation of the lateral and vertical extent of soil and rock layers at the site is based on the findings of our boring DH-101 and the ESP (2004) borings. Preliminary recommended soil parameters (e.g., soil unit weights, friction angles, shear strength) were developed on the basis of preliminary findings from boring DH- 101, boring blowcount data, field strength test data, and review of laboratory test data presented in ESP (2004). We understand that Quincy will use the information provided in Tables 3 through 5 in preliminary LPILE analyses to evaluate the general performance of piles at the abutments and center pier subjected to lateral loading. Sloping ground and group effects should be considered in the evaluation as needed. We note that the LPILE analyses may be sensitive to particular parameters presented herein and we recommend regular communication between Quincy and Fugro during the analyses and review of these parameters following the completion of our laboratory testing program. In addition, we recommend further interaction between the project team to confirm the approach is appropriate and consistent with AASHTO (2012) and Caltrans (2014a, 2014b) bridge design guidelines. Project No. 04.62120100 August 11, 2015 6 Table 3. Preliminary Engineering Parameters Recommended for North Abutment LPILE Layer Elevation Interval (feet) Soil type for p-y curve model in LPILE Total Unit Weight / (Submerged Unit Weight)1 (pcf) Undrained Shear Strength (psf) Friction Angle (degrees) 1 (af/Qal1) 112 --2 105 (43) -- -- 102 2 (Qal2) 102 API SAND 100 (38) -- 35 83 3 (Qal3) 83 SOFT CLAY (Matlock) 100 (38) 600 -- 74 4 (Qpr) 74 API SAND 110 (48) -- 35 28 5 (Qpr) 28 MODIFIED STIFF CLAY W/O FREE WATER 125 (63) 4700 -- 17.5 Notes: 1. Use total unit weight above water table and submerged unit weight below water table. Fugro analyses assumed water table at El. 85 ft. 2. Unit encountered above the proposed pile cap elevation and therefore not evaluated for axial or lateral capacity Table 4. Preliminary Engineering Parameters Recommended for South Abutment LPILE Layer Elevation Interval (feet) Soil type for p-y curve model in LPILE Total Unit Weight / (Submerged Unit Weight)1 (pcf) Undrained Shear Strength (psf) Friction Angle (degrees) 1 (af/Qal1) 110 API SAND 95 (33) -- 30 86 2 (Qal2) 86 API SAND 100 (38) -- 35 77 3 (Qal3) 77 SOFT CLAY (Matlock) 100 (38) 600 -- 44 4 (Qpr) 44 API SAND 110 (48) -- 35 33 Notes: 1. Use total unit weight above water table and submerged unit weight below water table. Fugro analyses assumed water table at El. 85 ft. Project No. 04.62120100 August 11, 2015 7 Table 5. Preliminary Engineering Parameters Recommended for Center Pier LPILE Layer Elevation Interval (feet) Soil type for p-y curve model in LPILE Total Unit Weight / (Submerged Unit Weight)1 (pcf) Undrained Shear Strength (psf) Friction Angle (degrees) 1 (af/Qal1) 94 --2 105 (43) -- -- 89 2 (Qal2) 89 API SAND 100 (38) -- 35 75.5 3 (Qal3) 75.5 SOFT CLAY (Matlock) 100 (38) 600 -- 50 4 (Qpr) 50 API SAND 110 (48) -- 35 28 5 (Qpr) 28 MODIFIED STIFF CLAY W/O FREE WATER 125 (63) 4700 -- --3 Notes: 1. Use total unit weight above water table and submerged unit weight below water table. Fugro analyses assumed water table at El. 85 ft. 2. Unit encountered to depth just below the proposed pile cap elevation and therefore not evaluated for axial or lateral capacity 3. Material properties below EL. 17-1/2 were extrapolated and assumed to be similar to the hard clay encountered at the bottom of boring DH-101. ATTENUATION RESPONSE SPECTRUM (ARS) The preliminary recommended design ARS is shown on Plate 3. We note the ARS data presented herein is an update of the ARS data presented in the Fugro (2012) Preliminary Foundation Report. The seismic conditions for this project will be further discussed in the design-level report. The site is proximal to a number of faults considered to be seismic sources within the Caltrans fault database. The closest source to the site is the San Luis Range fault system that is mapped along Highway 101 approximately ¼ mile west of the site. Preliminary seismic design criteria were estimated for the site using ARS Online and guidelines set forth in Appendix B of the Caltrans (2013) Seismic Design Criteria. The site coordinates were estimated to be 35.1226 degrees latitude and -120.5786 degrees longitude. The site response is controlled by deterministic estimates of ground motion occurring on either the San Luis Range fault system or the Los Osos fault. The estimated peak ground acceleration for the bridge site is approximately 0.68g. The site response for periods less than about 0.3 second is controlled by a M6.9 earthquake on the Los Osos fault, mapped approximately 3 miles east of the site. The site response for periods greater than about 0.3 seconds is controlled by a M7.1 earthquake on the San Luis Range fault system. An average shear wave velocity of approximately 300 meters/sec was estimated for the top 100 feet of soil at the site, which corresponds to a Soil Profile Type D. CLOSURE We appreciate the opportunity to provide this memorandum. As indicated above, the estimated pile tip elevation for the center bent pier extends below the geotechnical depths explored for this project and by ESP (2004). We recommend this issue be discussed with the project team and that a supplemental drilling program be considered to obtain geotechnical Project No. 04.62120100 August 11, 2015 8 subsurface data below the pile tip elevation or an alternative design for the center pier be evaluated to allow for a reduced pile embedment length. Please contact us if you have any questions or would like to discuss these findings in greater detail. Project No. 04.62120100 August 11, 2015 9 REFERENCES American Association of State Highway and Transportation Officials (AASHTO 2008), AASHTO LRFD Bridge Specifications, Chapter 10, with Caltrans amendments. California Department of Transportation (Caltrans, 2014a), Memo to Designers 3-1, Deep Foundations, June. Caltrans (2014b), California Amendments (to the AASHTO LRFD Bridge Design Specification, 6th Edition). Caltrans (2013b), Seismic Design Criteria, Version 1.7, April 2013, Division of Engineering Services, Structures Design. Earth Systems Pacific (ESP 2004), Conceptual Soils Engineering Report, Bridge Street Bridge, Bridge Street at Arroyo Grande Creek, Arroyo Grande, California, File No. SL-14066-SA, consultant report prepared for John L. Wallace & Associates, dated March 26, 2004. Ensoft, Inc. (2012), “Lpile 2012.6.37, a program for analyzing stress and deformation of individual piles or drilled shafts under lateral load”, Austin, Texas. Ensoft, Inc. (2012), “SHAFT 2012.7.10, a program for analyzing the axial capacity and short- term settlement of drilled shafts under axial load”, Austin, Texas. Fugro Consultants (2012), Preliminary Foundation Report “Bridge Street Bridge over Arroyo Grande Creek (Bridge No. 49c-0196), Arroyo Grande,California”, Project No. 04.6212.0100, dated November 28. Quincy Engineering, Inc. (2015) email titled “Bridge Street Bridge”, dated July 23. ^_Site Location 5780000 5780000 5790000 57900002230000 22300002240000224000022500002250000Quincy Engineering Project No. 04.62120100 VICINITY MAP Bridge St. Bridge Replacement Arroyo Grande, California PLATE 1 Service Layer Credits: Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp., NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), TomTom, MapmyIndia, © OpenStreetMap contributors, and the GIS User Community Ü 1:48,000 0 4,000 8,0002,000 Feet N:\Projects\04_2015\04_6215_0059_MontecitoUSD\Outputs\2015_07_13_GeotechReport\mxd\Plate1_VicinityMap.mxd, 7/28/2015, cdean !<!<!<!PArroyo Grande CreekB rid g e S tre e tOlohan AlleyAA'B-3B-2B-1DH-10180808080808085858585859090909090909595959510010010010010010010510510551051 101101101 1 0 110110115Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AEX, Getmapping, Aerogrid,IGN, IGP, swisstopo, and the GIS User Community579040057904005790600579060057908005790800224060022406002240800224080022410002241000Quincy EngineeringProject No. 04.62120100EXPLORATION LOCATION MAP Bridge St. Bridge Replacement Arroyo Grande, CaliforniaPLATE 2Ü06012030Feet1:600LegendTopography Contours!PApproximate Fugro 2015 Boring Location!<Approximate Earth Systems 2004Boring LocationMajor ContourMinor ContourN:\Projects\04_2012\04_6212_0100_BridgeStBridge\Outputs\2015_07_20_GeotechReport\mxd\Plate2_Expl_Plan.mxd, 8/5/2015, cdeanBase MapCross Section Location Quincy Engineering Project No. 04.62120100 1.6 08 1.0 1.2 1.4 leration, Sa (g)Estimated Shear Wave Velocity: 300 m/s Site Coordinates: 35.1226 lat -120.5786 long Los Osos Maximum Magnitude: 6.9 So. San Luis Range Maximum Magnitude: 7.1 Spectral Damping = 5 percent 0.2 0.4 0.6 0.8 Spectral Acce0.0 0.2 00.511.522.533.544.55 Period , T (sec) Los Osos Deterministic Spectrum T(sec) Sa(g) 0.01 0.678 Southern San Luis Range Deterministic Spectrum Probabilistic Response Spectrum PGA of Design Response Spectrum = 0.68g Design Response Spectrum 0.05 0.821 0.1 1.037 0.15 1.196 0.2 1.285 0.25 1.311 0.3 1.309 0.4 1.336 05 1 3420.5 1.342 0.6 1.326 0.7 1.313 0.85 1.263 1 1.202 1.2 1.044 1.5 0.858 2 0 595 DESIGN ACCELERATION RESPONSE SPECTRUM Bridge Street Bridge Replacement 2 0.595 3 0.326 4 0.210 5 0.160 Bridge Street Bridge Replacement Arroyo Grande, California PLATE 3 Bridge Street at Arroyo Grande Creek Bridge Project Report Replacement or Rehabilitation Project Appendix F - Preliminary Hydraulics Data April 2013 Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek City of Arroyo Grande, San Luis Obispo County, California Federal Aid Project No. BRLO-5199 (027) Bridge No. 49C-0196 Draft Bridge Design Hydraulic Study Report Prepared for: Prepared by: April 2013 Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek City of Arroyo Grande, San Luis Obispo County, California Federal Aid Project No. BRLO-5199 (027) Bridge No. 49C-0196 Draft Bridge Design Hydraulic Study Report Submitted to: City of Arroyo Grande This report has been prepared by or under the supervision of the following Registered Engineer. The Registered Civil Engineer attests to the technical information contained herein and has judged the qualifications of any technical specialists providing engineering data upon which recommendations, conclusions, and decisions are based. ________________________________________ Han-Bin Liang, Ph.D., P.E. Registered Civil Engineer ________________________________________ Date Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 i Table of Contents Executive Summary .......................................................................................................iii Acronyms.......................................................................................................................vi 1 General Description.........................................................................................1 1.1 Project Description...........................................................................................1 1.2 Key Tasks........................................................................................................3 1.3 Design Criteria.................................................................................................3 1.3.1 Hydrologic Design Criteria.............................................................................3 1.3.2 Hydraulic Design Criteria...............................................................................3 1.3.3 Scour Design Criteria......................................................................................4 1.4 Vertical Datum ................................................................................................4 2 Description of Watershed.................................................................................5 2.1 Geographic Location........................................................................................5 2.2 Watershed Size ................................................................................................5 2.3 Land Use .........................................................................................................6 3 Description of Stream and Site.........................................................................7 3.1 Channel Properties...........................................................................................7 3.2 Existing Bridge................................................................................................8 3.3 Proposed Bridge...............................................................................................9 4 Hydrology......................................................................................................10 4.1 Federal Emergency Management Agency ......................................................10 4.2 United States Geological Survey Study..........................................................10 4.3 Log-Pearson Type III Statistical Analysis ......................................................11 4.4 USGS Regional Flood-Frequency Equations..................................................12 4.5 Peak Discharges: Summary and Selection for Hydraulic Analysis..................12 4.6 Hydrologic Stability.......................................................................................13 5 Hydraulic Analysis ........................................................................................14 5.1 Design Tools..................................................................................................14 5.2 Cross Section Data.........................................................................................14 5.3 Model Boundary Condition............................................................................15 5.4 Manning’s Roughness Coefficients................................................................15 5.5 Expansion and Contraction Coefficients.........................................................16 5.6 Water Surface Elevations...............................................................................16 5.7 Freeboard.......................................................................................................19 5.8 Flow Velocities..............................................................................................20 5.9 Rock Slope Protection for Erosion Protection at Slope Embankments............21 6 Scour Analysis...............................................................................................22 6.1 Caltrans Bridge Inspection Reports................................................................22 6.2 Existing Channel Bed.....................................................................................22 6.3 Long-Term Bed Elevation Change.................................................................22 6.4 Contraction Scour..........................................................................................23 6.5 Abutment Scour.............................................................................................24 6.6 Total Scour and Scour Countermeasures........................................................25 6.6.1 Total Scour Depths.......................................................................................25 6.6.2 Scour Countermeasures ................................................................................26 Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 ii 6.6.3 Federal Highway Administration RSP Design...............................................27 6.6.4 California Bank and Shore RSP Design ........................................................27 6.6.5 Selected Class of RSP and Layer Thickness..................................................28 7 References.....................................................................................................29 Figures Figure 1. Project Location Map .......................................................................................1 Figure 2. Project Vicinity Map ........................................................................................2 Figure 3. Project Aerial Map ...........................................................................................2 Figure 4. Project Watershed Map.....................................................................................5 Figure 5. Project Land Use Map......................................................................................6 Figure 6. Annual Peak Flows Recorded at Upstream Gaging Station.............................11 Figure 7. Location of Lopez Lake and Dam Relative to Project Site..............................13 Figure 8. Stream Survey Cross Section Locations..........................................................14 Figure 9. Arroyo Grande Creek Stream Profile..............................................................15 Figure 10. 100-Year Water Surface Comparison............................................................17 Figure 11. 50-Year Water Surface Comparison..............................................................18 Figure 12. Upstream Face of Existing Bridge, Looking Downstream (Southwest).........19 Figure 13. Upstream Face of Proposed Bridge, Looking Downstream (Southwest)........19 Figure 14. Arroyo Grande Creek Stream Measurements at Upstream Face of Bridge Street Bridge .................................................................................................................23 Tables Table 1. Peak Discharges Summary for Arroyo Grande Creek.......................................13 Table 2. 100-Year Water Surface Elevations Summary Table........................................16 Table 3. 50-Year Water Surface Elevations Summary Table..........................................16 Table 4. Available Freeboard for the 100-year Storm Event...........................................20 Table 5. Available Freeboard for the 50-year Storm Event.............................................20 Table 6. 100-year Velocities in Vicinity of Project ........................................................20 Table 7. 50-year Velocities in Vicinity of Project ..........................................................21 Table 8. Summary of Total Scour Depths for Proposed Bridge......................................25 Table 9. Scour Elevations at Project Site for Spread Footings........................................26 Table 10. Scour Elevations at Project Site for Deep Foundations with Footings or Caps26 Photos Photo 1. Channel Downstream (Southwest) of Bridge Facing Downstream.....................7 Photo 2. Channel Upstream (Northeast) of Bridge Facing Upstream................................8 Photo 3. Existing Bridge..................................................................................................9 Appendices Appendix A HEC-RAS Results for Existing Bridge Appendix B HEC-RAS Results for Proposed Bridge Appendix C Scour Calculations Appendix D Rock Slope Protection Calculations Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 iii Executive Summary The Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek (Project) is located in the City of Arroyo Grande in the southwestern part of San Luis Obispo County, California. The Project proposes to retrofit or replace the existing bridge. The new bridge will be designed by Quincy Engineering, Inc. The purpose of this report is to summarize the hydrology, compare the hydraulics at the existing and proposed replacement bridges, present the estimated scour depths at the proposed bridge, and provide recommendations for scour countermeasures. The hydrology adopted for this study was estimated using United States Geological Survey (USGS) data from a nearby gaging station, which is located approximately 0.6 mi upstream (northeast) of the Project site. A statistical analysis using the Log-Pearson Type III distribution to fit the USGS data was performed to estimate the 100- and 50-year peak discharges at the Project site. The peak discharges at the gaging station were adjusted to obtain the peak discharges at the Project site by applying an adjustment factor based on the watershed areas at the respective locations. The resulting peak discharges at the Project site are listed in the table below: Arroyo Grande Creek Hydrology at Bridge Street Bridge Return Period Design Discharge (cfs*) 100-year 12,900 50-year 9,030 Note: *cfs = cubic ft per second There are currently four rehabilitation alternatives. Alternative A is a conventional replacement, Alternative B involves salvaging and relocating the existing truss, Alternative C is a replacement in kind, and Alternative D is a retrofit of the existing bridge. Alternatives A and B are the likely preferred alternatives, and therefore, were included in this study. Only one model hydraulic was generated that is applicable to replacement Alternatives A and B because the geometries of both alternatives are identical in terms of hydraulics. The proposed clear-span replacement bridge was modeled to be 110 ft long (hydraulic opening perpendicular to flow) by 60 ft wide (in the flow direction). The water surface elevations in the vicinity of the Project are reduced slightly in the proposed condition upstream of the bridge. The existing bridge does not meet freeboard requirements; the proposed bridge would meet freeboard requirements per the California Department of Transportation (Caltrans) and Federal Highway Administration’s (FHWA) hydraulic freeboard criteria. The water surface elevations and available freeboard for the existing and proposed bridges are summarized in the following table. The available freeboard for the proposed bridge increases dramatically due to changes to the hydraulic opening. The existing bridge has one pier, while the proposed bridge has no piers, and the bridge soffit and deck Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 iv for the proposed bridge are higher than the soffit and deck for the existing bridge. Note also that because the soffit elevation of the exist ing bridge was based on the lower brown truss that the existing bridge is a lot thicker than the proposed bridge. Existing and Proposed Conditions Hydraulic Summary Water Surface Elevation (ft NGVD 29) Return Period Bridge Condition Bridge Soffit Elevation1 (ft NGVD 29) 2 At Common Upstream Location3 At Upstream Face of Bridge Freeboard at Upstream Face of Bridge (ft) Existing 98.5 99.0 98.7 -0.2 100-year Proposed 105.5 98.7 98.7 6.8 Existing 98.5 96.1 95.9 2.6 50-year Proposed 105.5 95.9 95.9 9.6 Notes: 1 The soffit elevation for the existing bridge presented is based on the elevation of the lower brown truss. 2 NGVD 29 = National Geodetic Vertical Datum of 1929 3 The common upstream location is at River Station 1050, which is located 31 ft from the upstream face of the existing bridge and 14 ft from the upstream face of the proposed bridge. Preliminary scour calculations were performed based on the FHWA’s Hydraulic Engineering Circular No. 18, Evaluating Scour at Bridges (HEC-18). The hydraulic characteristics for the 100-year storm event from the hydraulic analysis and an assumed median grain size diameter of 0.075 mm were used to calculate the potential scour depths for the proposed alternative. The scour calculations are performed assuming that the channel bed material is erodible. Based on the two available stream measurements from Caltrans’ Bridge Inspection Reports from the years 1993 and 1999, and compared with the 2012 survey, the channel thalweg appears to be relatively stable. The total scour depths are summarized in the table below. Estimated Scour at Proposed Bridge Location Bridge Component Contraction Scour (ft) Long-Term Bed Change (ft) Local Scour (ft) Total Scour Depth (ft) Right Overbank, North Abutment 1 0 0 0 0 Left Overbank, South Abutment 2 0 0 3.9 3.9 Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 v For abutment foundations that are spread footings supported on soil, the top of the footing should be referenced to the thalweg of the channel and below the sum of the long- term degradation and contraction scour (in this case, 0 at both abutments). This approach requires the use of a designed countermeasure to prevent scour from developing at the base of the abutment. Because the thalweg is located at an approximate elevation of 76.7 ft NGVD 29, the top of the spread footing would need to be at least at or below that elevation. For deep foundations with footings or pile caps, the top of the footing or pile cap should be below the streambed at a depth equal to the long-term degradation and contraction scour depth (in this case, 0 at both abutments) and the bottom of the pile cap should be below the total scour depth. The minimum elevations for the deep foundations are summarized in the table below. Elevations at Project Site for Deep Foundations with Footings or Caps Location Bridge Component Ground Elevation at Abutment (ft NGVD 29) Top of Footing Elevation (ft NGVD 29) Bottom of Footing Elevation (ft NGVD 29) Right Overbank, North Abutment 1 98.8 98.8 98.8 Left Overbank, South Abutment 2 97.3 97.3 93.4 Rock slope protection (RSP) calculations were performed based on the FHWA’s Hydraulic Engineering Circular No. 23, Bridge Scour and Stream Instability Countermeasures: Experience, Selection, and Design Guidance, Third Edition (HEC-23) and checked using the California Bank and Shore Rock Slope Protection Design (Caltrans, 2000). The sizing of the RSP was based on the assumption that the channel side slopes under the replacement bridge will be 1.5:1 (H:V). Based on the calculations from both methods, ¼ ton class RSP is recommended to be placed at the abutments. Light class RSP has a median particle diameter that is 1.8 ft. The minimum layer thickness of 3.3 ft is recommended for ¼ ton class RSP unless bedrock is present at the site. If bedrock is present at the locations of the proposed abutment foundations, the RSP layer thickness can be thinner, and the RSP should be installed down to the naturally stable material. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 vi Acronyms BIR Bridge Inspection Reports Caltrans California Department of Transportation City City of Arroyo Grande D50 median grain size EPA Environmental Protection Agency FEMA Federal Emergency Management Agency FHWA Federal Highway Administration FIS Flood Insurance Study HEC-18 Hydraulic Engineering Circular No. 18 HEC-23 Hydraulic Engineering Circular No. 23 HEC-RAS Hydrologic Engineering Centers River Analysis System NGVD 29 National Geodetic Vertical Datum of 1929 Project Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek RSP rock slope protection U.S. 101 State Route 101 USACE U.S. Army Corps of Engineers USGS United States Geological Survey Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 1 1 GENERAL DESCRIPTION 1.1 Project Description The City of Arroyo Grande (City) proposes to replace or rehabilitate the existing Arroyo Grande Creek bridge (Bridge No. 49C-0196) at Bridge Street (see Figure 1 for the Project Location Map). Bridge Street follows a north-south corridor approximately 0.2 miles east of State Route 101 (U.S. 101) in the City of Arroyo Grande (see Figure 2 for the Project Vicinity Map and Figure 3 for the Project Aerial Map). Arroyo Grande Creek bridge provides vehicular access over Arroyo Grande Creek, which runs through the City approximately parallel to State Route 227. The surrounding land is generally level and is composed primarily of an urbanized business district. Figure 1. Project Location Map Source: United States Geological Survey (USGS) The existing bridge is structurally deficient and was posted for only 3 tons in 1985. This is the lowest posting allowed before bridge closure is required. The Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek (Project) need is to provide a new or rehabilitated bridge that will increase the load carrying capacity and also improve public safety. If the bridge is not rehabilitated or replaced, the condition will continue to deteriorate and eventually, bridge closure will be required. PROJECT LOCATION Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 2 Figure 2. Project Vicinity Map Source: USGS Figure 3. Project Aerial Map Source: Google Earth PROJECT LOCATION PROJECT LOCATION Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 3 The proposed Project will rehabilitate or replace the bridge on the existing alignment. As a result, road closure is proposed during the construction phase. Depending on the alternative selected, road closure may be required for up to 6 months. There are currently four rehabilitation alternatives. Alternative A is a conventional replacement, Alternative B involves salvaging and relocating the existing truss, Alternative C is a replacement in kind, and Alternative D is a retrofit of the existing bridge. Alternatives A and B are the likely preferred alternatives, and therefore, were included in this study. 1.2 Key Tasks Key tasks performed in this study included: 1) a review of available hydrologic data, 2) a hydrologic study, 3) a hydraulic analysis to determine design water surface elevations and flow velocities for the existing and proposed Bridge Street bridge over Arroyo Grande Creek, 4) a scour analysis to estimate potential scour depths, and 5) scour countermeasure analyses and recommendations. 1.3 Design Criteria 1.3.1 Hydrologic Design Criteria At least two hydrologic analysis methods were required for the Project per the Local Assistance Program Guidelines from Caltrans. WRECO used: 1. Published design discharges from the Federal Emergency Management Agency’s (FEMA) Flood Insurance Study (FIS) for San Luis Obispo County, California and Incorporated Areas, 2. Published design discharges from the Methods for Determining Magnitude and Frequency of Floods in California, Based on Data through Water Year 2006, 3. Statistical distribution analysis of stream flow data from a nearby gaging station, and 4. USGS Regional Regression calculations. 1.3.2 Hydraulic Design Criteria The hydraulic design of the bridge should follow the Federal Highway Administration (FHWA) and California Department of Transportation’s (Caltrans) criteria. The FHWA criterion for the hydraulic design of bridges is that they be designed to pass the 2% probability of annual exceedance flow (50-year recurrence interval design discharge) with adequate freeboard, where practicable, to account for debris and bedload. The Caltrans criteria for the hydraulic design of bridges is that they be designed to pass the 2% probability of annual exceedance flow (50-year design discharge) or the flood of record, whichever is greater, with adequate freeboard to pass anticipated drift. Two ft of freeboard is commonly used in preliminary bridge designs. The bridge should also be Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 4 designed to pass the 1% probability of annual exceedance flow (100-year design discharge, or base flood). No freeboard is added to the base flood. 1.3.3 Scour Design Criteria The evaluation of potential scour at the proposed bridge will follow the criteria described in the FHWA’s Hydraulic Engineering Circular No. 18 (HEC-18), Evaluating Scour at Bridges (Fifth Edition). The evaluation of potential scour shall be based on the 100-year design discharge hydraulic characteristics. The total scour was estimated based upon the cumulative effects of the long-term bed elevation change, general (contraction) scour, and local scour. The life expectancy of the bridge was considered in determining the long-term bed elevation change of the waterway. The long-term bed elevation change was based on an assumed 75-year design life for a new replacement bridge. 1.4 Vertical Datum The Project references the National Geodetic Vertical Datum of 1929 (NGVD 29). Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 5 2 DESCRIPTION OF WATERSHED 2.1 Geographic Location The Project site is located downstream of Huasna Road and 0.2 mi upstream (northeast) of U.S. 101 within the City of Arroyo Grande. Although the Project site is within an urban area, the upper reaches of the watershed are within a rural area. Arroyo Grande Creek begins in the Santa Lucia Range. The watershed is entirely within the southwestern portion of San Luis Obispo County. The Project site is located approximately 4 mi upstream of Arroyo Grande Creek’s outfall at Pismo State Beach. 2.2 Watershed Size The watershed that drains to the Project site is approximately 106 square mi. The watershed that drains to the Project site is shown in Figure 4. Figure 4. Project Watershed Map Source: USGS PROJECT LOCATION Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 6 2.3 Land Use The land use in the immediate Project vicinity is urban within the City of Arroyo Grande (see Figure 5). The land use designations for the watershed that drains to the Project site are a combination of: open space, rural lands, recreation, public facility, residential rural, and residential suburban. The upper reaches of the watershed are predominantly rural and open space while the lower reaches of the watershed are predominantly urban. Figure 5. Project Land Use Map Source: San Luis Obispo County, Google Earth, and Environmental Protection Agency (EPA) NORTH NO SCALE Watershed boundary Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 7 3 DESCRIPTION OF STREAM AND SITE 3.1 Channel Properties Although the area surrounding the Project site is predominantly developed, the channel within the Project vicinity is heavily vegetated with trees and vines. At the time of WRECO’s field visit in August 2012, there was water in the creek. The vegetation and water in the creek can be seen in Photo 1 and Photo 2. Photo 1. Channel Downstream (Southwest) of Bridge Facing Downstream Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 8 Photo 2. Channel Upstream (Northeast) of Bridge Facing Upstream 3.2 Existing Bridge The existing bridge is a hybrid structure composed of an original steel, Pratt pony, through truss that is now supported by a supplemental steel deck truss (see Photo 3). The structure also has a single southern approach span consisting of a reinforced concrete deck supported by steel stringers. The main truss span is approximately 100 ft long, and the approach span is approximately 24 ft long. Two seat type abutments and a single pier support the northern end of the approach span and southern end of the main truss. The pier consists of one approximately 4-ft diameter reinforced concrete pile extension under each truss bearing. The original 24 ft wide pony truss was built in 1908 and carries two traffic lanes with pedestrian sidewalks cantilevered on both sides outside of the truss members. An unknown time later, a large flow event in Arroyo Grande Creek washed out the southern approach embankment. The existing southern abutment was left in the channel and now serves as the intermediate pier. A new steel stringer approach span and concrete abutment were constructed on the newly formed southern embankment. The sidewalks are composed of timber oriented transversely and supported on steel brackets attached to the truss and approach span stringers. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 9 Photo 3. Existing Bridge 3.3 Proposed Bridge Section 1.1 describes the retrofit and replacement alternatives considered for the Project. One hydraulic model was generated that is applicable to both Alternatives A and B because the geometries of both alternatives are identical in terms of hydraulics. The proposed clear-span replacement bridge was modeled to be 110 ft long (hydraulic opening perpendicular to flow) by 60 ft wide (in the flow direction). The discussions that follow will refer to the two alternatives as simply the “proposed bridge.” Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 10 4 HYDROLOGY The hydrology at the Project site is presented in the following sections. As stated in Section 1.3.1, four methods were used to estimate the design discharges at the Project site: 1) research of FEMA’s FIS, 2) research of previous study by USGS, 3) statistical distribution analysis of stream flow data from a nearby gaging station, and 4) USGS Regional Regression calculations. 4.1 Federal Emergency Management Agency FEMA’s effective FIS (2012) presents the peak discharges for Arroyo Grande Creek, which FEMA determined from an analytical frequency curve that was derived from 28 years of record from USGS gage No. 11141500, at the City of Arroyo Grande. Three flooding locations are listed for Arroyo Grande Creek. Peak Discharges (cfs) Flooding Location Drainage Area (sq. mi.) 500-year 100-year 50-year 10-year Arroyo Grande Avenue 138.6 41,000 15,800 10,000 2,800 U.S. Highway 101 109.3 27,800 10,500 6,700 1,900 Huasna Road 82.5 25,800 8,700 5,100 1,100 The Project site is located between U.S. 101 and Huasna Road. 4.2 United States Geological Survey Study The USGS re-evaluated the magnitude and frequency of floods in California in a study published in 2012 (Gotvald et. al.). Annual peak flow data were analyzed for 771 stream flow gaging stations in California based on data through the water year 2006. Using the Bulletin 17B method of analysis, the study generated flood-frequency estimates for these gaging stations. Gaging station 11141500, which is located 0.6 mi upstream (northeast) of the Project site, was included in this analysis. The flood-frequency estimate for station 11141500, as published in the Gotvald et. al. study, was 11,300 cfs for the 100-year storm and 8,220 cfs for the 50-year storm. The annual peak flows recorded at station 11141500 are presented in Figure 6. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 11 Figure 6. Annual Peak Flows Recorded at Upstream Gaging Station Source: USGS Because the gaging station is not located at the Project site, the design discharges were adjusted using a basin transfer method based on the watershed areas at the gaging station and at the Project site. With this adjustment, the 100-year flow was estimated to be 11,670 cfs, and the 50-year flow was estimated to be 8,490 cfs. 4.3 Log-Pearson Type III Statistical Analysis WRECO also performed an independent analysis, and estimated design flows for Arroyo Grande Creek using USGS gaging station 11141500, which is located approximately 0.6 mi upstream (northeast) of the Project site. The gaging station has 47 years of data recorded from the water years 1940 through 1986. The annual peak discharges were analyzed statistically and fit into the Log-Pearson Type III distribution. Based on this analysis, the 100-year flow was estimated to be 12,490 cfs, and the 50-year flow was estimated to be 8,740 cfs. Because the gaging station is not located at the Project site, the design discharges were adjusted using a basin transfer method based on the watershed areas at the gaging station and at the Project site. With this adjustment, the 100-year flow was estimated to be 12,900 cfs, and the 50-year flow was estimated to be 9,030 cfs. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 12 4.4 USGS Regional Flood-Frequency Equations Flood-frequency equations were developed by the USGS and based on analysis of data from gage stations. California is divided into six regions; the Project site is within the Sierra Nevada region. These flood-frequency equations are generally used to estimate stream flow for ungaged sites that are not affected by substantial urban development and that are natural (unregulated) streams. On July 18, 2012, the USGS released updated regional flood-frequency equations, and revised the boundaries of the six unique regions within California. These equations are based on annual peak-flow data through water year 2006 for 771 streamflow-gaging stations in California having 10 or more years of data. The updated equations were used in support of the Project’s hydrologic analysis. The flood-frequency equations are as follows (Gotvald et. al., 2012): 994.084.0 100 0.11 PAQ= 15.184.0 50 32.5 PAQ= Where: Qx = peak discharge for a storm event with a return period of x years, cfs A = drainage area, square mi P = mean annual precipitation, in The resulting flows were 12,750 cfs for the 100-year storm and 10,090 cfs for the 50-year storm. 4.5 Peak Discharges: Summary and Selection for Hydraulic Analysis The peak discharges estimated using the Log-Pearson Type III analysis were selected to be the design discharges for the Project. The USGS regional flood-frequency analysis is generally used for sites that are not affected by substantial urban development that are natural and unregulated. The majority of the watershed is rural, and the immediate Project vicinity is developed. However, Lopez Lake is located within the watershed, approximately 9 mi upstream of the mouth to the Pacific Ocean (see Figure 7). Lopez Lake is a reservoir that is formed by Lopez Dam. Because the flow is regulated, the regional flood-frequency analysis may not be as appropriate for the Project. The other methods of analysis estimated the flows at the Project site using the upstream USGS gaging station 11141500 (with the exception of the USGS regional flood- frequency analysis). The FEMA study only included 28 years of record. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 13 Figure 7. Location of Lopez Lake and Dam Relative to Project Site Source: USGS The flows estimated by USGS in their previous study were comparable to the independent analysis using the Log-Pearson Type III analysis. The slightly larger flows estimated following the Log-Pearson Type III analysis were used to be conservative. Table 1. Peak Discharges Summary for Arroyo Grande Creek Method/Source 100-year Flow (cfs) 50-year Flow (cfs) FEMA at Upstream U.S. 101* 10,500 6,700 Previous USGS Study with Area Adjustment 11,670 8,490 Log-Pearson Type III with Area Adjustment 12,900 9,030 USGS Regional Flood- Frequency Equations 12,750 10,090 Note: * The flows listed for the FEMA source are not at the Project site and were not adjusted. 4.6 Hydrologic Stability Based on the land use map from San Luis Obispo County, as shown in Figure 5 in Section 2.3, the future land use for the watershed looks consistent with current conditions. The immediate Project vicinity is already developed, and the upper watershed looks to be predominantly rural. NORTH NO SCALE PROJECT LOCATION Lopez Lake Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 14 5 HYDRAULIC ANALYSIS The hydraulic design of the bridge will follow FHWA and Caltrans’ criteria. The following sections describe the development of the hydraulic modeling and summarize the results for the existing and proposed Bridge Street bridges at Arroyo Grande Creek. The water surface profile plots, hydraulic summary tables, and channel cross sections are included in Appendix A for the existing bridge and Appendix B for the proposed bridge. 5.1 Design Tools The hydraulics at the Project site were evaluated using the Hydrologic Engineering Centers River Analysis System (HEC-RAS) modeling software Version 4.1.0 developed by the U.S. Army Corps of Engineers (USACE). 5.2 Cross Section Data The channel geometry for the hydraulic model was developed using topographic survey data provided by McMillan Land Surveys in 2012. Six stream cross sections were surveyed and included in the hydraulic model (see Figure 8). The existing bridge was modeled as described in Section 3.2, and the proposed bridge was modeled as described in Section 3.3. Although the existing bridge superstructure consists of two trusses, the deck was modeled to be solid. Figure 8. Stream Survey Cross Section Locations Source: Google Earth NORTH NO SCALE PROJECT LOCATION Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 15 5.3 Model Boundary Condition The hydraulic model was evaluated using the steady state flow analysis and known downstream water surface elevations based on information from the FEMA FIS (see Figure 9). Figure 9. Arroyo Grande Creek Stream Profile Source: FEMA The most downstream cross section surveyed for the Project is coincident with the upstream face of the U.S. 101 structure (northbound). Therefore, the water surface elevations at that structure were used as the downstream boundary condition in the hydraulic model. Figure 9 graphically depicts the water surface elevations for the 100- year (long dash followed by two short dashes) and 50-year (long dash followed by one short dash) storm events. The water surface elevations at U.S. 101 northbound are 93 ft NGVD 29 for the 100-year event and 90 ft NGVD 29 for the 50-year event. 5.4 Manning’s Roughness Coefficients Manning’s roughness coefficients were used in the hydraulic model to represent the frictional energy losses in the flow. The roughness coefficients were selected to best describe the channel and the banks based on aerial imagery and observations made during WRECO’s site visit on August 22, 2012. Based on these observations, the roughness 100-year =93 ft NGVD 29 50-year =90 ft NGVD 29 Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 16 coefficients selected to describe the stream were 0.035 for the low flow channel and between 0.09 and 0.1 for the overbank areas. In the vicinity of the bridge, an average roughness coefficient of 0.04 was selected. 5.5 Expansion and Contraction Coefficients Expansion and contraction coefficients were used in the hydraulic model to estimate hydraulic losses at transitions between cross sections. The expansion and contraction coefficients used in the channel were 0.3 and 0.1, respectively. These values represent a channel with gradual transitions between cross sections. 5.6 Water Surface Elevations The water surface elevations were estimated for the existing and proposed conditions. The 100- and 50-year water surface profiles comparing the existing and proposed conditions are depicted in Figure 10 and Figure 11, respectively. The water surface elevations in the immediate vicinity of the bridges are compared in Table 2 and Table 3 for the 100-year and 50-year storm events, respectively. Because the proposed bridge is wider than the existing bridge, the upstream faces of the bridges are not at a common location. The nearest common upstream cross sectio n is at river station 1050, and is presented in the water surface elevations summary tables. The cross sections at the upstream faces of the existing and proposed structures are shown in Figure 12 and Figure 13, respectively. Table 2. 100-Year Water Surface Elevations Summary Table Water Surface Elevation (ft NGVD 29) River Station Description Existing Proposed 1050 Upstream 99.0 98.7 1037 Upstream face proposed N/A 98.7 1019 Upstream face existing 98.7 N/A 978 Downstream face proposed N/A 98.6 995 Downstream face existing 98.7 N/A 964 Downstream 98.6 98.6 Table 3. 50-Year Water Surface Elevations Summary Table Water Surface Elevation (ft NGVD 29) River Station Description Existing Proposed 1050 Upstream 96.1 95.9 1037 Upstream face proposed N/A 95.9 1019 Upstream face existing 95.9 N/A 978 Downstream face proposed N/A 95.8 995 Downstream face existing 95.9 N/A 964 Downstream 95.8 95.8 Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 17 Figure 10. 100-Year Water Surface Comparison Proposed Bridge Existing Bridge Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 18 Figure 11. 50-Year Water Surface Comparison Proposed Bridge Existing Bridge Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 19 The hydraulic modeling indicates that the proposed bridge would result in decreases in water surface elevation. The existing bridge has one pier, while the proposed bridge will have no piers. The proposed bridge will have a larger hydraulic opening than the existing bridge. These geometric differences result in the decreases in water surface elevation. Figure 12. Upstream Face of Existing Bridge, Looking Downstream (Southwest) Figure 13. Upstream Face of Proposed Bridge, Looking Downstream (Southwest) 5.7 Freeboard The freeboard requirements applicable to the Project are discussed in Section 1.3.2. To summarize, the bridge should be designed to pass the 50-year storm event with adequate freeboard to account for debris and bedload, or the 100-year storm event with no freeboard. The available freeboard distances (clearance distance from soffit to the water surface elevation) for the existing and proposed bridge structures are summarized in Table 4 for the 100-year storm event and Table 5 for the 50-year storm event. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 20 Table 4. Available Freeboard for the 100-year Storm Event Alternative Soffit Elevation* (ft NGVD 29) 100-Year Water Surface Elevation (ft NGVD 29) Freeboard (ft) Existing 98.5 98.7 -0.2 Proposed 105.5 98.7 6.8 Note: * The soffit elevation for the existing bridge presented is based on the elevation of the lower brown truss. Table 5. Available Freeboard for the 50-year Storm Event Alternative Soffit Elevation* (ft NGVD 29) 50-Year Water Surface Elevation (ft NGVD 29) Freeboard (ft) Existing 98.5 95.9 2.6 Proposed 105.5 95.9 9.6 Note: * The soffit elevation for the existing bridge presented is based on the elevation of the lower brown truss. The existing bridge does not meet the freeboard requirement of passing the 100-year storm event. The proposed bridge would meet the freeboard requirements by passing both the 50-year storm event with at least 2 ft of freeboard and the 100-year storm event. The available freeboard for the proposed bridge increases dramatically due to changes to the hydraulic opening. The existing bridge has one pier, while the proposed bridge has no piers, and the bridge soffit and deck for the proposed bridge are higher than the soffit and deck for the existing bridge. Note also that because the soffit elevation of the existing bridge was based on the lower brown truss that the existing bridge is a lot thicker than the proposed bridge. 5.8 Flow Velocities Flow velocities were estimated for the existing and proposed conditions. The 100- and 50-year flow velocities for the existing and proposed conditions are presented in Table 6 and Table 7, respectively. The proposed condition results in a very slight increase in velocity upstream of the bridge due to the lowering of the water surface elevation. Table 6. 100-year Velocities in Vicinity of Project Velocity (ft/s) River Station Description Existing Proposed 1050 Upstream 8.4 8.7 1037 Upstream face proposed N/A 8.4 1019 Upstream face existing 9.1 N/A 978 Downstream face proposed N/A 8.4 995 Downstream face existing 8.6 N/A 964 Downstream 8.5 8.5 Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 21 Table 7. 50-year Velocities in Vicinity of Project Velocity (ft/s) River Station Description Existing Proposed 1050 Upstream 7.4 7.6 1037 Upstream face proposed N/A 7.4 1019 Upstream face existing 7.8 N/A 978 Downstream face proposed N/A 7.3 995 Downstream face existing 7.4 N/A 964 Downstream 7.4 7.4 5.9 Rock Slope Protection for Erosion Protection at Slope Embankments The average channel flow velocities for the 100-year storm event in the vicinity of the proposed bridge are approximately 8 to 9 ft/s, which are considered to be erosive. Therefore, rock slope protection (RSP) was evaluated as an option to provide erosion protection at the proposed abutment locations. RSP calculations were performed using the methodologies presented in the California Bank and Shore Rock Slope Protection Design (Caltrans, 2000). The RSP is also considered a scour countermeasure, and the sizing of the RSP is discussed in Section 6.6. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 22 6 SCOUR ANALYSIS WRECO evaluated bridge scour per the criteria described in the FHWA HEC-18. The minimum design criterion for bridge scour is the 100-year design storm. WRECO evaluated the scour potential using the results of the steady state flow analysis from HEC- RAS for the proposed bridge. The scour calculations assume that the channel bed material is erodible. The following sub-sections summarize the results of the analysis, and the detailed calculations are included in Appendix C. 6.1 Caltrans Bridge Inspection Reports The Caltrans Bridge Inspection Reports (BIRs) from the years 1939 through 2011 were reviewed for relevant scour information. A bridge Scour Plan of Action that was prepared in October 2010 indicates that if the bridge is not replaced, “repair of the bridge deck is much more critical than a concern with scour.” The National Bridge Inventory Item 113 Code for the bridge is “U”, which represents a bridge with unknown foundation elevations that has not been evaluated for an appropriate scour rating. Two stream measurements were found in the BIRs from the May 13, 1993 and May 12, 1998 bridge inspections. These stream measurements were used to assess the long-term bed elevation change, as discussed in Section 6.3. 6.2 Existing Channel Bed The Draft Preliminary Foundation Report prepared by Fugro Consultants, Inc. for the Project describes the soils based on three borings that were drilled at the site from a previous study by Earth Systems Pacific. Based on the previous study, the subsurface soils at the Project site are “medium dense to dense silty and clayey sand and stiff clay.” Based on this description, a median grain size (D50) equivalent to a no. 200 sieve (0.075 mm) was assumed for the scour calculations. 6.3 Long-Term Bed Elevation Change Channel bed elevations may fluctuate over time as a result of changes in local sediment transport capacity and availability. In general, channel aggradation occurs when more sediment is supplied by watershed erosion and upstream channel flow than can be transported locally, and channel degradation occurs when sediment transport capacity exceeds supply. Only channel degradation is considered for the purposes of analyzing scour. As stated previously in Section 6.1, the long-term bed elevation change for the Project was determined by reviewing the available stream measurements from the Caltrans BIRs, and comparing with the topographic survey for the Project (see Figure 14 for a comparison of the three cross sections). Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 23 Figure 14. Arroyo Grande Creek Stream Measurements at Upstream Face of Bridge Street Bridge Source: McMillan Land Surveys (2012), and Caltrans (1999 and 1993) The two stream cross sections were measured relative to different reference points, which made it difficult to compare the cross sections. The 1993 cross section was measured relative to the top of the rail, while the 1999 stream cross section was measured relative to the top of the sidewalk. A comparison of the cross sections shows some changes in the bed elevation that could be due to variations in the way the data was captured. The thalweg appeared to be relatively stable. Because the upstream face of the replacement bridge will be at a slightly different location, the bridge should continue to be monitored to assess the long-term bed changes. 6.4 Contraction Scour Contraction (ultimate) scour occurs when the flow area of a stream is reduced either by: 1) the natural contraction of the stream channel; 2) by a bridge structure; or 3) the overbank flow forced back to the channel by roadway embankments at the roadway approach to a bridge. From the continuity equation, a decrease in flow area results in an increase in average velocity and bed shear stress through the contraction. Hence, there is an increase in erosive forces in the contracted section, and more bed material is removed from the contracted reach than is transported into the reach. This increase in transport of bed material from the reach lowers the natural bed elevation. As the bed elevation is lowered, the flow area increases. Thus, the velocit y and shear stress decrease until relative equilibrium is reached; i.e., the quantity of bed material that is transported into the reach is equal to that removed from the reach, or the bed shear stress is decreased to a Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 24 value such that no sediment is transported out of the reach. Contraction scour, in a natural channel or at a bridge crossing, involves removal of material from the bed across all or most of the channel width (FHWA 2001). As described in Section 6.2, the D50 was assumed to be 0.075 mm. Because of the small grain size at the Project site, ultimate scour for cohesive (silt and clay) materials was estimated using a relationship between the median grain size and the critical shear stress. The equation for estimating ultimate scour, as presented in HEC-18, is as follows: -=-3/1 11 2 1 83.194.0 gny K gy Vyy c u ults Where: ultsy- = scour depth for cohesive soils, ft 1y = average depth in the upstream main channel, ft 2V = average flow velocity in the contracted section, ft/s g = gravitational acceleration, 32.2 ft/s2 uK = 1.486 for U.S. Customary units, and 1.0 for S.I. units c = critical shear stress, lbs/ft2 = density of sediment, slugs/ft3 n = Manning’s roughness coefficient, unitless With a density of 2.6 to 3.2 slugs per cubic ft, the ultimate scour was calculated to be 9.2 ft. 6.5 Abutment Scour Abutment scour occurs when the bridge abutments block approaching flow. Abutment scour is commonly evaluated using either the Froehlich or HIRE live-bed scour equation. The HIRE equation is applicable when the ratio of the projected abutment length (the L parameter) to the flow depth (the y1 parameter) is greater than 25. The Froehlich equation was used for the scour analysis because the ratio of the projected abutment length to the flow depth was less than 25 for the abutment. Abutment 1, the northern abutment, was located just above the 100-year water surface elevation, and therefore, local scour was not evaluated at the abutment. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 25 The Froehlich equation is given below: +=1'27.2 61.0 21 Fr y LKKyy a as Where: =sy Scour depth, ft =1K Abutment shape coefficient (from Table 7.1 of HEC-18) =2K Coefficient for skew angle of abutment to flow ='L Length of active flow obstructed by the embankment, ft =Fr Froude number, based on the velocity and depth adjacent to and upstream of the abutment =ay Average depth of flow at the abutment = Ae/L, ft =L Length of embankment projected normal to the flow, ft =eA Flow area of the approach cross section obstructed by the embankment, ft2 The local abutment scour was estimated to be 3.9 ft at the southern abutment (Abutment 2). The scour calculation assumes that the channel bed material is erodible. 6.6 Total Scour and Scour Countermeasures 6.6.1 Total Scour Depths The total scour depths are the sum of the long-term bed elevation change, contraction scour, and local abutment scour. The long-term bed elevation change was found to be negligible based on available information. The calculated scour depths are presented in Table 8. Table 8. Summary of Total Scour Depths for Proposed Bridge Location Bridge Component Contraction Scour (ft) Local Scour (ft) Total Scour Depth (ft) Right Overbank, North Abutment 1 9.2 0 9.2 Left Overbank, South Abutment 2 9.2 3.9 13.1 For abutment foundations that are spread footings supported on soil, the top of the footing should be referenced to the thalweg of the channel, and below the sum of the long-term degradation and contraction scour. This approach requires the use of a designed countermeasure to prevent scour from developing at the base of the abutment. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 26 The scour elevations for the spread footings are summarized in Table 9, and the scour countermeasures are discussed in Section 6.6.2. Table 9. Scour Elevations at Project Site for Spread Footings Location Bridge Component Thalweg Elevation (ft) Long-Term and Contraction Scour Depth (ft) Scour Elevation (ft) Right Overbank, North Abutment 1 76.7 9.2 67.5 Left Overbank, South Abutment 2 76.7 9.2 67.5 For deep foundations with footings or pile caps, the top of the footing or pile cap should be below the streambed at a depth equal to the long-term degradation and contraction scour depth. Lower footing elevations should be considered when the piles could be damaged by erosion and corrosion. The bottom of the pile cap should be below the total scour depth. The scour elevations for the deep foundations are summarized in Table 10. Table 10. Scour Elevations at Project Site for Deep Foundations with Footings or Caps Location Bridge Component Ground Elevation at Abutment (ft) Top of Footing Elevation (ft) Bottom of Footing Elevation (ft) Right Overbank, North Abutment 1 98.8 89.6 89.6 Left Overbank, South Abutment 2 97.3 88.1 84.2 6.6.2 Scour Countermeasures RSP generally consists of rocks on channel and structure boundaries to limit the effects of erosion. It is the most common type of scour countermeasure due to its general availability, ease of installation, and relatively low cost. Two procedures for determining RSP design were considered: the FHWA’s Hydraulic Engineering Circular No. 23, Bridge Scour and Stream Instability Countermeasures: Experience, Selection, and Design Guidance – Third Edition (HEC-23) (2009), and Caltrans’ California Bank and Shore Rock Slope Protection Design – Third Edition (2000). The following sub-sections summarize the results of the analysis, and the detailed calculations are included in Appendix D. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 27 6.6.3 Federal Highway Administration RSP Design The D50 of the RSP at the bridge abutment was calculated using the Ishbash relationship from HEC-23, Design Guideline 14. The following equation was used to determine the median stone diameter required for the proposed riprap erosion control system to protect the channel slope under the bridge: For Froude numbers (V/(gy)0.5) 0.80 (HEC-23, equation 14.1): -= gy V S K y D s 2 50 1 Where: D50 = median stone diameter, ft V = characteristic average velocity in the contracted section, ft/s Ss = specific gravity of rock riprap (2.65) g = gravitational acceleration (32.2 ft/s2) y = depth of flow in the contracted bridge opening, ft K = 1.02 for a vertical wall abutment The median stone diameter is a function of velocity and depth. The average channel flow velocities and flow depths for the 100-year storm event from the hydraulic analysis were used to calculate the minimum required median stone diameter of the RSP to protect the banks in the vicinity of the bridge. The minimum RSP for the proposed bridge was calculated to be ¼ ton class. 6.6.4 California Bank and Shore RSP Design The third edition of the California Bank and Shore Rock Slope Protection Design (Caltrans 2000) was also used to analyze RSP design criteria: )(sin)1( 00002.0 33 6 arSG SGVW R R -×- ××= Where: V = 2/3 average stream velocity for flows parallel to the bank, ft/s 4/3 average stream velocity for flows which impinge the bank, ft/s RSG = specific gravity of the stones (2.65) r = 70° for broken rock (constant) a = angle of face slope from the horizontal W = RSP weight The Arroyo Grande Creek flow path in the Project vicinity is roughly parallel to the proposed abutment faces, and therefore, the velocit y is considered parallel to the bank. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 28 The angle of face slope was assumed to be 1.5:1 (horizontal to vertical). The average channel flow velocities for the 100-year storm event from the hydraulic analysis were used to calculate the minimum required RSP weights. The minimum RSP for the proposed bridge was calculated to be light class RSP. 6.6.5 Selected Class of RSP and Layer Thickness The larger ¼ ton RSP class calculated following the FHWA HEC-23 guidelines is proposed at the Project site, which has a median particle diameter of 1.8 ft. The RSP layer thickness should be designed per the California Bank and Shore RSP Design manual (Caltrans 2000). A minimum layer thickness of 3.3 ft is recommended for ¼ ton class RSP, but the RSP layer thickness can be thinner where there is bedrock, and the RSP should be installed down to the naturally stable material. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 29 7 REFERENCES California Department of Transportation. (2000). California Bank and Shore Rock Slope Protection Design – Practitioner’s Guide and Field Evaluations of Riprap Methods. Final Report No. FHWA-CA-TL-95-10. Caltrans Study No. F90TL03. Third Edition – Internet. October 2000. California Department of Transportation – Division of Maintenance – Structure Maintenance and Investigations. (2012, 1999, 1993). Bridge Inspection Report. Bridge Number: 49C0196. Facility Carried: Bridge St. Location: 0.1 mi S of S.R. 227. Federal Emergency Management Agency (2004). Flood Insurance Study, Sacramento County, California and Incorporated Areas. Flood Insurance Study Number 060304V002A. Federal Highway Administration. (2012). Hydraulic Engineering Circular No. 18, Evaluating Scour at Bridges (Fifth Edition) Federal Highway Administration. (2009). Hydraulic Engineering Circular No. 23, Bridge Scour and Stream Instability Countermeasures: Experience, Selection, and Design Guidance, Third Edition. Federal Highway Administration. (2004). Code of Federal Regulations. Title 23 – Highways. Sub-chapter G – Engineering and Traffic Operations. Part 650 – Bridges, Structures, and Hydraulics. Google Earth. (2013). (Last accessed: April 3, 2013). Gotvald, A.J., Barth, N.A., Veilleux, A.G., and Parrett, Charles, 2012, Methods for determining magnitude and frequency of floods in California, based on data through water year 2006: U.S. Geological Survey Scientific Investigations Report 2012–5113, 38 p., 1 pl., available online only at <http://pubs.usgs.gov/sir/2012/5113/>. McMillan Land Surveys. (2012). Topographic survey of channel cross sections. San Luis Obispo County. (2013). Planning and Building – Zoning and Maps – Map Image Download Center – Land Use Maps. <http://www.slocounty.ca.gov/planning/zoning/Map_Image_Download_Center/L and_Use_Maps.htm> (Last accessed: March 27, 2013) United States Army Corps of Engineers – Hydrologic Engineering Center. (2010). River Analysis System. HEC-RAS. (Version 4.1.0) [Computer software]. January 2010. <http://www.hec.usace.army.mil/software/hec-ras/hecras-download.html> United States Geological Survey. (2012). National Map Viewer. <http://viewer.nationalmap.gov/viewer> (Last accessed: August 30, 2012) United States Geological Survey. (2001). California: Seamless USGS Topographic Maps (CDROM, Version 2.6.8, 2001, Part Number: 113-100-004). National Geographic Holdings, Inc. Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 Appendix A HEC-RAS Results for Existing Bridge 0200400600800100012001400708090100110Bridge Street Plan: ExistingMain Channel Distance (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundLOBROB269.885581.67790.854964.235*1007.2361265.726Arroyo Grande Cr Arroyo Grande Cr1 in Horiz. = 205 ft 1 in Vert. = 10 ft -100-500501008090100110Bridge Street Plan: Existing Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.1.09.035.09 -100-500501008090100110Bridge Street Plan: Existing INTERPOLATED ** Upstream of Alternative AStation (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.1.09.035.035.09.1 -100-500501008090100110Bridge Street Plan: Existing INTERPOLATED ** Upstream face Alternative AStation (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.1.09.035.09.11 in Horiz. = 25 ft 1 in Vert. = 30 ft1 -100-500501008090100110Bridge Street Plan: Existing Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundIneffBank Sta.1.04.1 -100-500501008090100110Bridge Street Plan: Existing Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundIneffBank StaPier Debris.1.04.1 -100-500501008090100110Bridge Street Plan: Existing Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundIneffBank Sta.1.04.11 in Horiz. = 25 ft 1 in Vert. = 30 ft2 -100-500501008090100110Bridge Street Plan: Existing Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundIneffBank Sta.1.04.1 -100-500501008090100110Bridge Street Plan: Existing INTERPOLATED ** Downstream face Alternative AStation (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.1.09.035.09.1 -100-500501008090100110Bridge Street Plan: Existing INTERPOLATED ** Downstream of Alternative AStation (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.1.09.035.09.11 in Horiz. = 25 ft 1 in Vert. = 30 ft3 -100-500501008090100110Bridge Street Plan: Existing Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.1.09.035.09.1 -100-500501008090100110Bridge Street Plan: Existing Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.09.035.09 -100-500501008090100110Bridge Street Plan: Existing Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.1.09.035.091 in Horiz. = 25 ft 1 in Vert. = 30 ft4 -100-500501008090100110Bridge Street Plan: Existing Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.1.09.035.091 in Horiz. = 25 ft 1 in Vert. = 30 ft5 HEC-RAS Plan: Ex-Incl-PrXSECs River: Arroyo Grande Cr Reach: Arroyo Grande CrReach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Arroyo Grande Cr 1265.726 50yr 9030.00 81.08 97.62 98.70 0.010858 8.35 1081.85 118.12 0.49Arroyo Grande Cr 1265.726 100yr 12900.00 81.08 100.57 101.81 0.009581 8.96 1440.23 125.04 0.47Arroyo Grande Cr 1050.23 50yr 9030.00 77.00 96.13 96.99 0.005658 7.44 1213.56 104.73 0.39Arroyo Grande Cr 1050.23 100yr 12900.00 77.00 99.01 100.12 0.006292 8.44 1527.85 113.56 0.41Arroyo Grande Cr 1035.23* 50yr 9030.00 76.72 96.08 96.89 0.005355 7.26 1244.13 104.39 0.37Arroyo Grande Cr 1035.23* 100yr 12900.00 76.72 98.94 100.01 0.006055 8.29 1555.89 113.02 0.39Arroyo Grande Cr 1022.236 50yr 9030.00 76.47 96.07 88.61 96.85 0.001420 7.09 1273.96 104.18 0.35Arroyo Grande Cr 1022.236 100yr 12900.00 76.47 98.92 90.77 99.97 0.001530 8.23 1567.04 112.60 0.37Arroyo Grande Cr 1007.236 BridgeArroyo Grande Cr 992.236 50yr 9030.00 76.47 95.93 88.60 96.73 0.001471 7.17 1259.56 103.76 0.36Arroyo Grande Cr 992.236 100yr 12900.00 76.47 98.73 90.77 99.81 0.001592 8.34 1546.95 112.03 0.38Arroyo Grande Cr 979.236 50yr 9030.00 76.48 95.87 96.69 0.005238 7.25 1244.76 103.04 0.37Arroyo Grande Cr 979.236 100yr 12900.00 76.48 98.69 99.77 0.006042 8.34 1547.04 111.50 0.39Arroyo Grande Cr 964.235* 50yr 9030.00 76.49 95.76 96.61 0.005501 7.39 1221.49 102.09 0.38Arroyo Grande Cr 964.235* 100yr 12900.00 76.49 98.56 99.68 0.006348 8.49 1518.90 110.63 0.40Arroyo Grande Cr 790.854 50yr 9030.00 76.66 94.35 95.50 0.007105 8.60 1050.28 94.67 0.45Arroyo Grande Cr 790.854 100yr 12900.00 76.66 96.81 98.35 0.008766 9.97 1294.21 104.01 0.50Arroyo Grande Cr 581.67 50yr 9030.00 75.87 94.06 94.46 0.002451 5.10 1771.37 162.02 0.27Arroyo Grande Cr 581.67 100yr 12900.00 75.87 96.54 97.08 0.002838 5.89 2188.37 173.33 0.29Arroyo Grande Cr 269.885 50yr 9030.00 74.17 91.78 92.88 0.013639 8.41 1073.17 142.54 0.54Arroyo Grande Cr 269.885 100yr 12900.00 74.17 94.04 95.31 0.014583 9.03 1428.02 172.34 0.55Arroyo Grande Cr 0 50yr 9030.00 72.30 90.00 84.80 90.72 0.004827 7.05 1611.13 369.36 0.39Arroyo Grande Cr 0 100yr 12900.00 72.30 93.00 86.97 93.55 0.003014 6.62 3010.70 563.79 0.32 Plan: Ex-Incl-PrXSECs Arroyo Grande Cr Arroyo Grande Cr RS: 1007.236 Profile: 50yr E.G. US. (ft) 96.85 Element Inside BR US Inside BR DS W.S. US. (ft) 96.07 E.G. Elev (ft) 96.83 96.74 Q Total (cfs) 9030.00 W.S. Elev (ft) 95.89 95.90 Q Bridge (cfs) 9030.00 Crit W.S. (ft) 88.71 88.64 Q Weir (cfs) Max Chl Dpth (ft) 19.42 19.43 Weir Sta Lft (ft) Vel Total (ft/s) 7.78 7.37 Weir Sta Rgt (ft) Flow Area (sq ft) 1160.79 1225.15 Weir Submerg Froude # Chl 0.39 0.37 Weir Max Depth (ft) Specif Force (cu ft) 10987.46 11220.28 Min El Weir Flow (ft) 109.26 Hydr Depth (ft) 12.62 12.51 Min El Prs (ft) 99.68 W.P. Total (ft) 144.23 129.66 Delta EG (ft) 0.12 Conv. Total (cfs) 173171.6 203416.3 Delta WS (ft) 0.14 Top Width (ft) 91.95 97.96 BR Open Area (sq ft) 1453.05 Frctn Loss (ft) 0.06 0.01 BR Open Vel (ft/s) 7.78 C & E Loss (ft) 0.03 0.01 Coef of Q Shear Total (lb/sq ft) 1.37 1.16 Br Sel Method Energy only Power Total (lb/ft s) -101.28 -101.28 Plan: Ex-Incl-PrXSECs Arroyo Grande Cr Arroyo Grande Cr RS: 1007.236 Profile: 100yr E.G. US. (ft) 99.97 Element Inside BR US Inside BR DS W.S. US. (ft) 98.92 E.G. Elev (ft) 99.94 99.83 Q Total (cfs) 12900.00 W.S. Elev (ft) 98.66 98.69 Q Bridge (cfs) 12900.00 Crit W.S. (ft) 91.10 90.88 Q Weir (cfs) Max Chl Dpth (ft) 22.19 22.22 Weir Sta Lft (ft) Vel Total (ft/s) 9.09 8.58 Weir Sta Rgt (ft) Flow Area (sq ft) 1418.56 1502.78 Weir Submerg Froude # Chl 0.34 0.39 Weir Max Depth (ft) Specif Force (cu ft) 16019.88 16391.57 Min El Weir Flow (ft) 109.26 Hydr Depth (ft) 18.22 14.84 Min El Prs (ft) 99.68 W.P. Total (ft) 174.21 139.55 Delta EG (ft) 0.16 Conv. Total (cfs) 213285.0 272229.1 Delta WS (ft) 0.19 Top Width (ft) 77.85 101.27 BR Open Area (sq ft) 1453.05 Frctn Loss (ft) 0.07 0.01 BR Open Vel (ft/s) 9.09 C & E Loss (ft) 0.04 0.02 Coef of Q Shear Total (lb/sq ft) 1.86 1.51 Br Sel Method Energy only Power Total (lb/ft s) -101.28 -101.28 Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 Appendix B HEC-RAS Results for Proposed Bridge 0200400600800100012001400708090100110Bridge Street Plan: ProposedMain Channel Distance (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundLOBROB269.885581.67790.854964.235*1007.2361265.726Arroyo Grande Cr Arroyo Grande Cr1 in Horiz. = 205 ft 1 in Vert. = 10 ft -100-500501008090100110Bridge Street Plan: Proposed Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.1.09.035.09 -100-500501008090100110Bridge Street Plan: Proposed INTERPOLATED ** Upstream of Alternative AStation (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundIneffBank Sta.1.09.035.035.09.1 -100-500501008090100110Bridge Street Plan: Proposed Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundIneffBank Sta.1.04.11 in Horiz. = 25 ft 1 in Vert. = 30 ft1 -100-500501008090100110Bridge Street Plan: Proposed Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundIneffBank Sta.1.04.1 -100-500501008090100110Bridge Street Plan: Proposed INTERPOLATED ** Downstream of Alternative AStation (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundIneffBank Sta.1.09.035.09.1 -100-500501008090100110Bridge Street Plan: Proposed Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.1.09.035.09.11 in Horiz. = 25 ft 1 in Vert. = 30 ft2 -100-500501008090100110Bridge Street Plan: Proposed Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.09.035.09 -100-500501008090100110Bridge Street Plan: Proposed Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.1.09.035.09 -100-500501008090100110Bridge Street Plan: Proposed Station (ft)Elevation NGVD 29 (ft)LegendWS 100yrWS 50yrGroundBank Sta.1.09.035.091 in Horiz. = 25 ft 1 in Vert. = 30 ft3 HEC-RAS Plan: ProposedAltA River: Arroyo Grande Cr Reach: Arroyo Grande CrReach River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl(cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) Arroyo Grande Cr 1265.726 50yr 9030.00 81.08 97.48 98.60 0.011359 8.47 1065.51 117.79 0.50Arroyo Grande Cr 1265.726 100yr 12900.00 81.08 100.33 101.63 0.010172 9.14 1410.87 124.49 0.48Arroyo Grande Cr 1050.23 50yr 9030.00 77.00 95.91 89.30 96.80 0.005952 7.58 1190.59 104.05 0.40Arroyo Grande Cr 1050.23 100yr 12900.00 77.00 98.72 91.53 99.88 0.006362 8.65 1491.61 112.67 0.41Arroyo Grande Cr 1007.236 BridgeArroyo Grande Cr 964.235* 50yr 9030.00 76.49 95.76 88.69 96.61 0.005501 7.39 1221.49 102.09 0.38Arroyo Grande Cr 964.235* 100yr 12900.00 76.49 98.55 90.91 99.67 0.006290 8.50 1517.88 110.61 0.40Arroyo Grande Cr 790.854 50yr 9030.00 76.66 94.35 95.50 0.007105 8.60 1050.28 94.67 0.45Arroyo Grande Cr 790.854 100yr 12900.00 76.66 96.81 98.35 0.008766 9.97 1294.22 104.01 0.50Arroyo Grande Cr 581.67 50yr 9030.00 75.87 94.06 94.46 0.002451 5.10 1771.37 162.02 0.27Arroyo Grande Cr 581.67 100yr 12900.00 75.87 96.54 97.08 0.002837 5.89 2188.38 173.33 0.29Arroyo Grande Cr 269.885 50yr 9030.00 74.17 91.78 92.88 0.013639 8.41 1073.17 142.54 0.54Arroyo Grande Cr 269.885 100yr 12900.00 74.17 94.04 95.31 0.014582 9.03 1428.04 172.34 0.55Arroyo Grande Cr 0 50yr 9030.00 72.30 90.00 84.80 90.72 0.004827 7.05 1611.13 369.36 0.39Arroyo Grande Cr 0 100yr 12900.00 72.30 93.00 86.97 93.55 0.003014 6.62 3010.70 563.79 0.32 Plan: ProposedAltA Arroyo Grande Cr Arroyo Grande Cr RS: 1007.236 Profile: 50yr E.G. US. (ft) 96.80 Element Inside BR US Inside BR DS W.S. US. (ft) 95.91 E.G. Elev (ft) 96.75 96.65 Q Total (cfs) 9030.00 W.S. Elev (ft) 95.91 95.82 Q Bridge (cfs) 9030.00 Crit W.S. (ft) 88.94 88.65 Q Weir (cfs) Max Chl Dpth (ft) 19.19 19.34 Weir Sta Lft (ft) Vel Total (ft/s) 7.36 7.28 Weir Sta Rgt (ft) Flow Area (sq ft) 1226.53 1239.67 Weir Submerg Froude # Chl 0.38 0.37 Weir Max Depth (ft) Specif Force (cu ft) 10966.39 11179.84 Min El Weir Flow (ft) 110.48 Hydr Depth (ft) 11.81 12.05 Min El Prs (ft) 106.44 W.P. Total (ft) 114.08 113.51 Delta EG (ft) 0.19 Conv. Total (cfs) 221957.0 226687.9 Delta WS (ft) 0.15 Top Width (ft) 103.88 102.90 BR Open Area (sq ft) 2316.95 Frctn Loss (ft) 0.10 0.04 BR Open Vel (ft/s) 7.36 C & E Loss (ft) 0.01 0.00 Coef of Q Shear Total (lb/sq ft) 1.11 1.08 Br Sel Method Energy only Power Total (lb/ft s) -98.82 -99.39 Plan: ProposedAltA Arroyo Grande Cr Arroyo Grande Cr RS: 1007.236 Profile: 100yr E.G. US. (ft) 99.88 Element Inside BR US Inside BR DS W.S. US. (ft) 98.72 E.G. Elev (ft) 99.82 99.71 Q Total (cfs) 12900.00 W.S. Elev (ft) 98.71 98.62 Q Bridge (cfs) 12900.00 Crit W.S. (ft) 91.14 90.84 Q Weir (cfs) Max Chl Dpth (ft) 21.99 22.14 Weir Sta Lft (ft) Vel Total (ft/s) 8.44 8.39 Weir Sta Rgt (ft) Flow Area (sq ft) 1528.26 1538.46 Weir Submerg Froude # Chl 0.40 0.39 Weir Max Depth (ft) Specif Force (cu ft) 16146.64 16378.58 Min El Weir Flow (ft) 110.48 Hydr Depth (ft) 13.92 14.04 Min El Prs (ft) 106.44 W.P. Total (ft) 121.37 121.62 Delta EG (ft) 0.21 Conv. Total (cfs) 307275.3 310271.4 Delta WS (ft) 0.17 Top Width (ft) 109.80 109.54 BR Open Area (sq ft) 2316.95 Frctn Loss (ft) 0.10 0.04 BR Open Vel (ft/s) 8.44 C & E Loss (ft) 0.00 0.00 Coef of Q Shear Total (lb/sq ft) 1.39 1.37 Br Sel Method Energy only Power Total (lb/ft s) -98.82 -99.39 Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 Appendix C Scour Calculations Bridge Street Bridge Replacement ProjectSan Luis Obispo, CaliforniaUltimate (Contraction) Scour100-year FlowCalculation guideline from HEC-18 5th EditionInput from HEC-RAS for Proposed Alternative A & B Page 6.15, Page 151 / 340 , Section 6.7 Contraction Scour in Cohesive Materials (6.7.1 Ultimate Scour) y1 13.6 ft 4.1 m Upstream depthV28.4 ft/s 2.6 m/s Average velocity in contracted sectiontcCritical shear stressn0.04 0.04 Manning's nKu1.486 1 1.486 fot U.S. Customary, and 1.0 for S.I.r slugs/ft3 Density 1000 kg/m3 =1.94 slugs/ft3g32.2 ft/s^2 9.81 m/s^2D500.075 mm Density, rhohttp://www.mo10.nrcs.usda.gov/references/guides/properties/moistbulkdensity.html Material DensityClay1350 kg/m3 2.62 slugs/ft3Very fine sand 1650 kg/m3 3.20 slugs/ft3Water, sea 1026 kg/m3 1.99 slugs/ft3Water, pure 1000 kg/m3 1.94 slugs/ft3 Critical Shear Stress Tc Tc (N/m2)Tc (lb/ft2)Tc=0.05(D50)^-0.4 0.1 Clay ,Tc=0.05(D50)^-0.4 Very fine sand ,Tc=0.05(D50)^-0.42.81 m 9.2 ft ys 2.82 m 9.2 ft ys 1243 Alpine Road, Suite 108 Walnut Creek, CA 94596 Phone: 925.941.0017 Fax: 925.941.0018 www.wreco.com Bridge Street Bridge Replacement ProjectSan Luis Obispo, CaliforniaLocal Scour at Abutments - Froehlich or HIRE 100-year FlowCalculation guideline from HEC-18 5th EditionInput from HEC-RAS for Proposed Alternative A & B Units = (SI or English)Englishg = acceleration due to gravity =32.2 ft/s^2 Left Overbank = Abutment #2 (South)y1 = depth of flow at abutment on the overbank or in the main channel =1.4 ftL = length of embankment projected normal to flow =12.9 ftRatio of projected embankment length to flow depth = L/y1 =9.214E+00Abutment scour equation to be used =Froehlich Froehlich's Live Bed Abutment Scour EquationL' = length of active flow obstructed by the embankment =2.5 ftAe = flow area of the approach cross section obstructed by the embankment =1.8 ft^2ya = average depth of flow on the flood plain = Ae/L'0.70 ft Qe = flow obstructed by the abutment and approach embankment =11 ft^3/sVe = flow velocity = Qe/Ae =6.2 ft/sFr = Froude Number of approach flow upstream of the abutment = 1.31Ө = abutment skew = 90 degreesK1 = coefficient for abutment shape =1 K2 = coefficient for angle of embankment shape = (Ө/90)^0.13 = 1 Ys = abutment scour = ya*(2.27*k1*k2*((L'/ya)^0.43)*(Fr^0.61)+1) =3.9 ft HIRE Live Bed Abutment Scour EquationV = velocity of flow at upstream face of abutment =ft/sFr = Froude Number = V/((g*y1)^.5) =n/aӨ = abutment skew = degreesK1 = coefficient for abutment shape = K2 = coefficient for angle of embankment shape = (Ө/90)^0.13 = n/aYs = abutment scour = y1*(4*(Fr^0.33)*(K1/0.55)*K2) =n/a ft Bridge St Scour Analysis.xls - Abutment-Froehlich or HIRE 4/3/2013 Draft Bridge Design Hydraulic Study Report Federal Aid Project No. BRLO-5199 (027) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek Bridge No. 49C-0196 City of Arroyo Grande, San Luis Obispo County, California April 2013 Appendix D Rock Slope Protection Calculations Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek, Proposed Alternatives A and BRock Slope Protection Calculations for Banks (California Bank and Shore Protection)Location Upstream Upstream Face Downstream Face DownstreamW (lb) 132 114 110 119RSP Class Light Light Light LightHEC-23D50 17 16 16 17 median stone diameter, inchesRSP Class 1/4 ton 1/4 ton 1/4 ton 1/4 ton rock classSelected RSP SizeOuter layer 1/4 ton 1/4 ton 1/4 ton 1/4 tonFabric Type B B B BThickness Per HEC-11Thickness should not be less than the larger of 1.5 times D50 or D100.D50 = 1.8 1.8 1.8 1.8 ft1.5 * D50 = 2.7 2.7 2.7 2.7 ftD100= 2.25 2.25 2.25 2.25 ftThickness Per CABS for outer layerThickness3.3 3.3 3.3 3.3ftPlacement B B B BInner layerNot required for 1/4 tonBackingCan be backing class no. 1 or 2.Backing 1 has a thickness of 1.8 ftBacking 2 has a thickness of 1.24 ftIf Light is selected intead of 1/4 ton, fabric type is A, with no inner layers, no backing, and a minimum thickness of 2.6 ft Rock Slope Protection Calculations for AbutmentsBridge Street Bridge Rehabilitation Project over Arroyo Grande Creek, Proposed Alternatives A and BLocation Upstream Upstream Face Downstream Face DownstreamV 8.7 8.4 8.4 8.5 ft/sg 32.2 32.2 32.2 32.2ft/s2y 13.6 13.9 14.0 13.8 ftFr 0.41 0.40 0.39 0.40IsbashIsbashIsbashIsbashfrom HEC-23For Froude Numbers (V/(gy)1/2)<=0.80, Isbash relationshipy 13.6 13.9 14.0 13.8 depth of flow in the contracted bridge opening, ftK 1.0 1.0 1.0 1.0 (1.02 for vertical wall abutment, 0.89 or for spill-through abutment)Ss2.7 2.7 2.7 2.7 specific gravity of rockV 8.7 8.4 8.4 8.5 average velocity in contracted section, ft/sg 32.2 32.2 32.2 32.2gravitational acceleration, ft/s2D501.4 1.4 1.4 1.4 median stone diameter, ftD5017.2 16.4 16.2 16.6 median stone diameter, inches1/4 ton1/4 ton1/4 ton1/4 tonrock classFor Froude Numbers (V/(gy)1/2)>0.80, Equation 14.2y 13.6 13.9 14.0 13.8 depth of flow in the contracted bridge opening, ftK 0.7 0.7 0.7 0.7 (0.61 for spill-through abutment, 0.69 or for vertical wall abutment)Ss2.7 2.7 2.7 2.7 specific gravity of rockV 8.7 8.4 8.4 8.5 average velocity in contracted section, ft/sg 32.2 32.2 32.2 32.2gravitational acceleration, ft/s2D50N/A N/A N/A N/A median stone diameter, ftD50N/A N/A N/A N/A median stone diameter, inches-=gyVSyKDs250)1( Rock Slope Protection Calculations for Banks (California Bank and Shore Protection) Bridge Street Bridge Rehabilitation Project over Arroyo Grande Creek, Proposed Alternatives A and B Location Upstream Upstream Face Downstream Face Downstream Storm Event 100-year 100-year 100-year 100-year VM (ft/s) 8.7 8.4 8.4 8.5 Flow Condition Impinging Impinging Impinging Impinging V (ft/s) 11.5 11.2 11.2 11.3 SG 2.7 2.7 2.7 2.7 r (degrees) 70 70 70 70 a (degrees) 34 34 34 34 W (lb) 131.7 113.7 109.7 118.6 RSP Class Light Light Light Light Location Upstream Upstream Face Downstream Face Downstream Storm Event 100-year 100-year 100-year 100-year VM (ft/s) 8.7 8.4 8.4 8.5 Flow Condition Parallel Parallel Parallel Parallel V (ft/s) 5.8 5.7 5.6 5.7 SG 2.7 2.7 2.7 2.7 r (degrees) 70 70 70 70 a (degrees) 34 34 34 34 W (lb) 2.2 1.9 1.8 1.9 RSP Class Backing No. 3 Backing No. 3 Backing No. 3 Backing No. 3 W = minimum rock mass, pounds VM = average channel velocity, ft/s V = velocity to which bank is exposed, ft/s (for impinging flow, multiply VM by 1.33) SG = specific gravity of rock r = 70 degrees (for randomly placed rubble, a constant) a = outside slope face angle with horizontal, degrees x y D (ft)= 1.5 1 q (a) = 33.69 )()1( 00002.0 33 6 arSINSG SGVW -- =