CAPAY DAM APRON REPLACEMENT PROJECT Initial Study / Mitigated Negative Declaration
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CAPAY DAM APRON REPLACEMENT PROJECT Initial Study / Mitigated Negative Declaration Prepared for May 2009 Yolo County Flood Control and Water Conservation District CAPAY DAM APRON REPLACEMENT PROJECT Initial Study / Mitigated Negative Declaration Prepared for May 2009 Yolo County Flood Control and Water Conservation District 2600 Capitol Avenue Suite 200 Sacramento, CA 95816 916.564.4500 www.esassoc.com Los Angeles Oakland Olympia Petaluma Portland San Diego San Francisco Seattle Tampa Woodland Hills 208607 TABLE OF CONTENTS Capay Dam Apron Replacement Project Page 1. Project Description 1-1 Introduction 1-1 CEQA Requirements 1-1 Responsible Agencies, Permits and Approvals 1-2 Project Location 1-2 Project Background 1-5 Project Objectives and Need 1-7 Project Description 1-7 2. Environmental Checklist Form 2-1 Environmental Factors Potentially Affected 2-2 Environmental Impacts 2-3 Aesthetics and Visual Resources 2-3 Agriculture Resources 2-5 Air Quality 2-6 Biological Resources 2-11 Cultural Resources 2-43 Geology, Soils, and Seismicity 2-52 Hazards and Hazardous Materials 2-56 Hydrology and Water Quality 2-60 Land Use and Land Use Planning 2-66 Mineral Resources 2-68 Noise 2-69 Population and Housing 2-75 Public Services 2-77 Recreation 2-79 Transportation/Traffic 2-80 Utilities and Service Systems 2-84 Mandatory Findings of Significance 2-86 3. Supporting Information Sources and List of Abbreviations 3-1 4. List of Preparers 4-1 Yolo County Flood Control and Water Conservation District 4-1 Environmental Science Associates 4-1 Capay Dam Apron Replacement Project i ESA/208607 Draft IS/MND May 2009 Table of Contents Page Appendices A. Construction Emissions Technical Data Sheets B. Wetland Delineation C. California Natural Diversity Database (CNDDB) Search Results D. California Native Plant Society’s Inventory of Rare and Endangered Plants E. Federal Endangered and Threatened Species List F. Capay Dam Restoration Project Cultural Resources Survey Report List of Figures 1-1 Regional Locator Map 1-3 1-2 Site and Vicinity Map 1-4 1-3 Site Photos 1-6 1-4 Proposed Site Plan 1-8 1-5 Typical Cross Section 1-9 1-6 Grade Control Structure Detail 1-10 2-1 Habitat Map 2-15 List of Tables 1-1 Regulatory Requirements, Permits, and Authorizations for Project Facilities 1-2 1-2 Summary of Proposed Construction Activities and Equipment 1-12 2-1 Air Quality Data Summary (2005–2008) For the Proposed Project Area 2-7 2-2 Summary of Modeled Max. Short-Term Construction-Generated Emissions 2-8 2-3 Habitat Types Within the Project Study Area 2-12 2-4 Potential Jurisdictional Features Within the Study Area 2-17 2-5 Potential Non-Jurisdictional Features Within the Study Area 2-18 2-6 List of Potentially Occurring Special-Status Species 2-26 2-7 USGS Gaging Stations along Cache Creek 2-61 2-8 Average Annual Runoff to Cache Creek at USGS Gaging Stations 2-62 2-9 Sources and Relative Amounts of Annual Groundwater Recharge 2-63 2-10 Typical Construction Noise Levels 2-72 2-11 Typical Noise Levels Generated by Construction Equipment 2-73 2-12 Vibration Velocities for Construction Equipment 2-74 Capay Dam Apron Replacement Project ii ESA/208607 Draft IS/MND May 2009 SECTION 1 Project Description Introduction The Yolo County Flood Control and Water Conservation District (YCFCWCD or District) is proposing to modify the dam apron on the Capay Diversion Dam to prevent the dam from overturning during normal operations or extreme events. The District is proposing to extend the apron from its existing 16 foot length downstream of the dam toe to a point about 60 feet downstream. The extended apron would be placed across the entire 450 foot width of the dam and include a new cutoff wall at the downstream end. The project also includes installation of a grade control structure approximately 150 feet downstream of the dam that is designed to protect the dam from the potential advance of downstream erosion and the long-term streambed degradation of Cache Creek. This Initial Study/Mitigated Negative Declaration (IS/MND) has been prepared to identify and assess the anticipated environmental effects of the proposed project. The District, as the California Environmental Quality Act (CEQA) lead agency, has determined that a Mitigated Negative Declaration is the appropriate environmental document for the proposed project. CEQA Requirements This document has been prepared to satisfy the requirements of the CEQA (Public Resources Code Section 21000 et seq.) and the State CEQA Guidelines (14 California Code of Regulations [CCR] 15000 et seq.). CEQA requires that all state and local government agencies consider the environmental consequences of projects over which they have discretionary authority before they approve or implement those projects. The Initial Study is a public document used by the District, acting as lead agency, to determine whether a proposed project may have a significant effect on the environment. If the District finds substantial evidence that any aspect of the project, either alone or in combination with other projects, may have a significant effect on the environment, the District is required to prepare an environmental impact report (EIR), a supplement to a previously prepared EIR, or a subsequent EIR to analyze the project at hand. If the District finds no substantial evidence that the project or any of its aspects may cause a significant impact on the environment, a negative declaration may be prepared. If, over the course of the analysis, the project is found to have a significant impact on the environment that, with specific mitigation measures, can be reduced to a less-than-significant level, a mitigated negative declaration may be prepared. Capay Dam Apron Replacement Project 1-1 ESA/208607 Draft IS/MND May 2009 Capay Dam Apron Replacement Project Responsible Agencies, Permits, and Approvals Table 1-1 summarizes the potential permits and/or approvals that may be required prior to construction of the proposed project. Additional local approvals and permits may be required. TABLE 1-1 REGULATORY REQUIREMENTS, PERMITS, AND AUTHORIZATIONS FOR PROJECT FACILITIES Agency Type of Approval Federal Agencies U.S. Army Corps of Engineers 404 Clean Water Act Permit State Agencies Regional Water Quality Control Board NPDES General Permit for Stormwater Discharge Associated with Construction Activities; 401Certification California Department of Fish and Game Streambed Alteration Agreement Local Agencies Yolo County Grading Permit Yolo-Solano Air Quality Management District Authority to Construct Project Location, Setting, and Existing Facilities The District is located in Western Yolo County and is bordered by Solano County to the South (Figure 1-1). The District service area encompasses a large portion of unincorporated western Yolo County and the cities of Woodland, Davis, and Winters, and the towns of Capay, Esparto, and Madison. The District delivers water stored in Clear Lake and Indian Valley Reservoir in Lake County for agricultural and municipal uses in Yolo County. Indian Valley Reservoir was constructed by the District and is located on the north fork of Cache Creek. Most of the water delivered is conveyed down Cache Creek and diverted out of the creek channel at Capay Dam. The Dam serves as the headworks for over 160 miles of irrigation canals within the District’s 195,000-acre jurisdiction. Typically the District delivers about 150,000 acre feet of water to about 55,000 acres of agricultural lands. The District’s Cache Creek water system is completely gravity-dependent and does not include any pumping facilities. The Capay Dam was built by the Yolo Water & Power Company in 1915. Water released from Clear Lake and Indian Valley Reservoir is diverted into the West Adams and the Winters canals at the Capay Diversion Dam, which are located to the north and south, respectively, of the dam. The Winters and West Adams canals feed the entire canal system. Figure 1-2 shows the extent of project study area, including the location of the Capay Dam and the grade control structure. The Capay Dam is used to divert water only during the irrigation season. Other times of the year water flowing down Cache Creek flows over the dam or through sluice gates without obstruction. During the irrigation season, typically mid April through early September, an inflatable bladder fitted to the top of the dam is filled, causing water to be ponded upsteam of the dam to a sufficient depth to flow through the canal headgates. Historically this ponding was achieved by installing flash boards on the top of the dam. The inflatable bladder was installed as a more efficient and safer method for managing the pond waters. 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