Boca Dam Safety of Dams Modification Project Environmental Assessment/Initial Study Environmental Assessment No. 15-03-MP Nevada County, California U.S. Department of the Interior California Regional Water Quality Control Board Bureau of Reclamation Lahontan Region Mid-Pacific Region Office Region 6 – South Lake Tahoe Office Sacramento, California South Lake Tahoe, California January 2018 [This page intentionally left blank] 0 Table of Contents SECTION 1 INTRODUCTION ..................................................................................................... 6 1.1 Background ................................................................................................................ 6 1.2 Need for Proposed Action/Proposed Project ............................................................ 7 1.3 Document Structure ................................................................................................... 8 1.4 Environmental Setting ................................................................................................ 8 1.4.1 Topography and Geology .............................................................................................................. 8 1.4.2 Weather.......................................................................................................................................... 9 1.4.3 Hydrology and Water Supply ....................................................................................................... 11 1.4.4 Water Quality ............................................................................................................................... 14 1.4.5 Air Quality .................................................................................................................................... 15 1.4.6 Biological Resources ................................................................................................................... 18 1.4.7 Recreational Activities .................................................................................................................. 21 1.4.8 Visual Resources ......................................................................................................................... 22 1.4.9 Traffic and Circulation .................................................................................................................. 22 1.4.10 Fire Danger .................................................................................................................................. 23 1.4.11 Cultural Resources ...................................................................................................................... 23 1.4.12 Waters of the U.S./Waters of the State ........................................................................................ 24 1.4.13 Noise ............................................................................................................................................ 24 SECTION 2 ALTERNATIVES ................................................................................................... 25 2.1 No Action Alternative ................................................................................................ 25 2.2 Proposed Action Alternative – Shear Key and Stability Berm .................................. 26 2.2.1 Schedule ...................................................................................................................................... 26 2.2.2 Reservoir Operations During Construction .................................................................................. 28 2.2.3 Spillway Modifications .................................................................................................................. 29 2.2.4 Site Preparation ........................................................................................................................... 30 2.2.5 Cutoff Wall, Shear Key, Stability Berm, and Embankment Overlay Construction ....................... 31 2.2.6 Road Use and Public Access....................................................................................................... 36 2.2.7 Haul Routes ................................................................................................................................. 40 2.2.8 In-Reservoir Borrow Area (IRBA)................................................................................................. 41 2.2.9 Staging and Stockpiling Areas ..................................................................................................... 42 2.2.10 Mitigation Measures for the Proposed Action Alternative ............................................................ 43 2.2.11 Obtaining Permits and Other Approvals ...................................................................................... 56 2.3 Reservoir Restriction Alternative .............................................................................. 57 2.3.1 Mitigation Measures for the Reservoir Restriction Alternative ..................................................... 59 2.4 Dam Breach Alternative ........................................................................................... 59 SECTION 3 EVALUATION OF ENVIRONMENTAL IMPACTS ................................................ 61 3.1 Resources Analyzed ................................................................................................ 61 3.1.1 Aesthetics .................................................................................................................................... 61 3.1.2 Agriculture and Forestry Resources ............................................................................................ 64 3.1.3 Air Quality .................................................................................................................................... 65 3.1.4 Biological Resources ................................................................................................................... 68 3.1.5 Cultural Resources ...................................................................................................................... 87 3.1.6 Geology and Soils ........................................................................................................................ 89 3.1.7 Greenhouse Gas Emissions ........................................................................................................ 91 3.1.8 Hazards and Hazardous Materials .............................................................................................. 92 3.1.9 Hydrology and Water Quality ....................................................................................................... 96 3.1.10 Land Use and Planning .............................................................................................................. 115 3.1.11 Mineral Resources ..................................................................................................................... 116 1 3.1.12 Noise .......................................................................................................................................... 117 3.1.13 Population and Housing ............................................................................................................. 121 3.1.14 Public Services .......................................................................................................................... 122 3.1.15 Recreation .................................................................................................................................. 124 3.1.16 Transportation/Traffic ................................................................................................................. 128 3.1.17 Utilities and Service Systems..................................................................................................... 131 3.1.18 Tribal Cultural Resources .......................................................................................................... 132 3.1.19 Mandatory Findings of Significance ........................................................................................... 133 SECTION 4 OTHER FEDERAL ENVIRONMENTAL COMPLIANCE REQUIREMENTS....... 138 4.1 Indian Sacred Sites ................................................................................................ 138 4.2 Indian Trust Assets ................................................................................................ 138 4.3 Environmental Justice ............................................................................................ 140 4.4 Consultation and Coordination ............................................................................... 141 SECTION 6 REFERENCES .................................................................................................... 142 2 Figures Page Figure 1 Location of Boca Dam 6 Figure 2 Features of Boca Dam 7 Figure 3 Profile of modeled dam deformation during 9 an earthquake Figure 4 Drought areas in the western United States 10 Figure 5 Little Truckee River Watershed within the 11 Lower Truckee River Watershed Figure 6 Hydrograph of Boca Reservoir since 2009 14 Figure 7 Air basin location 16 Figure 8 Attainment status for the NSAQMD 18 Figure 9 Concept Level Construction Schedule 27 Figure 10 Hypothetical Boca Reservoir Operation at Full Pool during Temporary Reservoir 29 Drawdown Figure 11 Proposed Action Alternative in-reservoir 30 borrow area (indicated in orange) Figure 12 Proposed Action Alternative