SUPPLEMENTAL ENVIRONMENTAL ASSESSMENT FOR DAM SAFETY INTERIM RISK REDUCTION MEASURES AND RESERVOIR DRAWDOWN AND OPERATIONS PLAN Anderson Dam Hydroelectric Project - FERC Project No. 5737-007 California Federal Energy Regulatory Commission Office of Energy Projects Division of Hydropower Administration and Compliance 888 First Street, NE Washington, D.C. 20426 February 2021 TABLE OF CONTENTS LIST OF FIGURES .......................................................................................................... iii LIST OF TABLES ............................................................................................................ iii 1.0 INTRODUCTION .................................................................................................... 1 1.1 Filing ....................................................................................................................... 1 1.2 Purpose of Action.................................................................................................... 1 1.3 Statutory and Regulatory Requirements ................................................................. 3 1.4 Public Review and Comment .................................................................................. 7 2.0 PROPOSED ACTION AND ALTERNATIVES ..................................................... 8 2.1 No-Action Alternative ............................................................................................ 8 2.2 Applicant’s Proposal ............................................................................................... 8 2.3 Staff Alternative with Recommended Measures .................................................. 19 3.0 ENVIRONMENTAL ANALYSIS ......................................................................... 20 3.1 Scope of Cumulative Effects Analysis ................................................................. 20 3.2 Proposed Action .................................................................................................... 22 i 4.0 CONCLUSIONS .................................................................................................... 111 4.1 Staff Recommended Measures ........................................................................... 111 4.2 Unavoidable Adverse Effects ............................................................................. 112 4.3 Consistency with Comprehensive Plans ............................................................. 114 5.0 FINDING OF NO SIGNIFICANT IMPACT ...................................................... 115 6.0 LITERATURE CITED .......................................................................................... 115 7.0 LIST OF PREPARERS ......................................................................................... 130 APPENDIX A ................................................................................................................. A-1 ii LIST OF FIGURES Figure 1: Location of proposed FERC Order Compliance Project actions ...................... 12 Figure 2: Location of low-level outlet and tunnel construction and creek channel modifications ............................................................................................... 13 Figure 3: Coyote Percolation Dam. ................................................................................ 14 Figure 4: Location of proposed levee and floodwalls between Mabury Road and the South Bay Mobile Home Park. .............................................................. 15 Figure 5: Location of proposed floodwalls between Mabury Road and Highway 101. .............................................................................................................. 16 Figure 6: Location of proposed flood mitigation measures between William Street Park and Santa Clara Street. ........................................................................ 17 Figure 7: Location of historic northern channel of Coyote Creek ................................... 18 Figure 8: Discharge exceedance probability curve .......................................................... 42 Figure 9: Predicted suspended sediment downstream of Anderson Dam for existing outlet and Anderson Dam Tunnel outlet with two-year inflow ........................................................................................................... 52 Figure 10: Anderson Lake County Park Recreation Sites and Facilities ......................... 88 Figure 11: Cross Valley Pipeline Extension Route .......................................................... 91 LIST OF TABLES Table 1: Fish found in Coyote Creek CWMZ and from Ogier Ponds to Highway 237 by family ............................................................................................... 38 Table 2: Passage conditions at Coyote Percolation Dam with flashboard dam ............... 42 Table 3: Flow distribution between channels in cfs ........................................................ 48 iii ACRONYMS AND ABBREVIATIONS ac-ft acre-feet ADSRP Anderson Dam Seismic Retrofit Project ADTP Anderson Dam Tunnel Project Advisory Council Advisory Council on Historic Preservation AFM Anderson Force Main AIS Aquatic Invasive Species AMM Avoidance and Minimization Measure APE Area of Potential Effects BAAQMD Bay Area Air Quality Management District BGEPA Bald and Golden Eagle Protection Act BMPs best management practices °C degrees Celsius CalFire California Department of Forestry and Fire Protection California DFG California Department of Fish and Game California DFW California Department of Fish and Wildlife California SHPO California State Historic Preservation Officer CalTrout California Trout CCC Central California Coast CCFPP Coyote Creek Flood Protection Project CEQ Council on Environmental Quality cfs cubic feet per second Commission or FERC Federal Energy Regulatory Commission Corps U.S. Army Corps of Engineers iv County Parks Santa Clara County Parks and Recreation Department CRLF California red-legged frog CWA Clean Water Act CWMZ Cold Water Management Zone CVP Cross Valley Pipeline deadpool reservoir elevation 488 feet D2SI the Commission’s Division of Dam Safety and Inspections DPS Distinct Population Segment EA Environmental Assessment eDNA environmental DNA EFH essential fish habitat EPA U.S. Environmental Protection Agency ESA Endangered Species Act ºF degrees Fahrenheit FAHCE agreement Fisheries and Aquatic Habitat Cooperative Effort Agreement FOCP FERC Order Compliance Project FPA Federal Power Act ft feet FWS U.S. Fish and Wildlife Service gpm gallons per minute HDMP Wetland and Riparian Habitat Dryback Monitoring Plan IRRM Interim Risk Reduction Measures mcy million cubic yards MW megawatts v µg/L micrograms/Liter mg/L milligrams/Liter MRL method reporting limit MOU Memorandum of Understanding MSA Magnuson-Stevens Fishery Conservation and Management Act MTBM micro tunnel boring machine NEPA National Environmental Policy Act NHPA National Historic Preservation Act NMFS National Marine Fisheries Service National Register National Register of Historic Places NTUs Nephelometric Turbidity Units October 1 EA EA issued on October 1, 2020 October 1 Order Order issued on October 1, 2020 Open Space Authority Santa Clara Valley Open Space Authority PA Programmatic Agreement PBFs physical and biological features PFMP Pacific Coast Salmon Fishery Management Plan PCBs polychlorinated biphenyl compounds PPMP Phytophthora Pathogen Management Plan Reclamation U.S. Bureau of Reclamation TSS total suspended solids TWG Fisheries Technical Work Group SCVHA Santa Clara Valley Habitat Agency SCVHP Santa Clara Valley Habitat Plan SCVWCD Santa Clara Valley Water Conservation District SDPS Southern Distinct Population Segment vi supplemental EA Supplemental Environmental Assessment Vaki computer-based fish counter Valley Water or exemptee Santa Clara Valley Water District Water Board California State Water Resources Control Board vii EXECUTIVE SUMMARY On October 1, 2020, Commission staff issued an Environmental Assessment (EA) focused on Santa Clara Valley Water’s (Valley Water, or exemptee) July 27, 2020 filing of a Reservoir Drawdown and Operations Plan, detailing how it proposed to implement dam safety interim risk reduction measures at the Anderson Dam in response to a February 20, 2020 directive from Commission staff. The October 1 EA focused on the drawdown of the reservoir and closely connected actions including reservoir rim stability improvements and mitigation including an extension to the Cross Valley Pipeline. Commission staff hereby supplement the October 1 EA to analyze the effects of those actions from the Reservoir Drawdown and Operations Plan not fully analyzed in the October 1 EA including the exemptee’s proposal to construct and operate a low-level outlet tunnel, reopen the north channel of Coyote Creek, replace the downstream Coyote percolation dam, and implement downstream flood control measures. Commission staff supplement the October 1 EA by adding additional analysis for the actions described above by resource area. The exemptee’s Reservoir Drawdown and Operations Plan, considered in full, will have adverse effects to water quantity, water quality, aquatic and terrestrial resources, recreation, cultural resources, and aesthetics. Valley Water proposed a number of best management practices (BMPs) and mitigation measures to reduce adverse effects. National Marine Fisheries Service (NMFS) and U.S. Fish and Wildlife Service (FWS) provided conservation recommendations to the Commission through emergency consultation