DRAFT Mitigated Negative Declaration SEPTEMBER 2020 Palo Alto Flood Basin Tide Gate Structure Replacement Project Valley Water Project No. 10394001 Palo Alto Flood Basin Tide Gate Structure Replacement Project Draft Mitigated Negative Declaration September 2020 Table of Contents : Introduction .............................................................................................. 1-1 Organization of this Document ................................................................................................ 1-1 Purpose of the Mitigated Negative Declaration ....................................................................... 1-1 Decision to Prepare a Mitigated Negative Declaration............................................................ 1-1 Public Review Process ........................................................................................................... 1-2 Interagency Collaboration and Regulatory Review ................................................................. 1-2 Project Description .................................................................................. 2-1 Project Background ................................................................................................................. 2-1 Project Objectives ................................................................................................................... 2-5 Project Description .................................................................................................................. 2-5 Project Design Development Process ................................................................................... 2-27 : Environmental Setting ............................................................................. 3-1 Project Location ...................................................................................................................... 3-1 Surrounding Land Uses .......................................................................................................... 3-1 Physical Environment ............................................................................................................. 3-1 Environmental Evaluation ....................................................................... 4-1 Aesthetics ............................................................................................................................... 4-3 Agriculture and Forestry Resources........................................................................................ 4-8 Air Quality ............................................................................................................................. 4-10 Biological Resources ............................................................................................................ 4-17 Cultural Resources ............................................................................................................... 4-68 Energy ................................................................................................................................... 4-74 Geology and Soils ................................................................................................................. 4-76 Greenhouse Gas Emissions ................................................................................................. 4-82 Hazards and Hazardous Materials ........................................................................................ 4-86 Hydrology and Water Quality ................................................................................................ 4-92 Land Use and Planning ....................................................................................................... 4-101 Mineral Resources .............................................................................................................. 4-104 Noise ................................................................................................................................... 4-106 Population and Housing ...................................................................................................... 4-113 Public Services ................................................................................................................... 4-114 Recreation ........................................................................................................................... 4-117 Transportation ..................................................................................................................... 4-124 Tribal Cultural Resources ................................................................................................... 4-129 Utilities and Service Systems .............................................................................................. 4-132 Wildfire ................................................................................................................................ 4-136 Mandatory Findings of Significance .................................................................................... 4-138 Report Preparation .................................................................................... 5-1 References ................................................................................................. 6-1 i Palo Alto Flood Basin Tide Gate Structure Replacement Project Draft Mitigated Negative Declaration September 2020 Figures Figure 2-1. Project Location ...................................................................................................... 2-3 Figure 2-2. Palo Alto Flood Basin and Vicinity .......................................................................... 2-4 Figure 2-3. Project Overview ................................................................................................... 2-11 Figure 2-4. Plan and Profile of New Tide Gate Structure ........................................................ 2-12 Figure 2-5. Trail Closure ......................................................................................................... 2-13 Figure 2-6. Staging and Access .............................................................................................. 2-14 Figure 2-7. Project Schedule and Phasing .............................................................................. 2-17 Figure 2-8. Overview of Options Evaluated ............................................................................ 2-31 Figure 3-1. Photo of Existing Tide Gate and Levee .................................................................. 3-2 Figure 4-1. Habitats in the Western Portion of the Study Area ............................................... 4-26 Figure 4-2. Habitats in the Eastern Portion of Study Area ...................................................... 4-27 Figure 4-3. CNDDB Plant Occurrences within 2 Miles of Project Area ................................... 4-30 Figure 4-4. CNDDB Fish and Wildlife Occurrences within 2 Miles of Project Area ................. 4-35 Figure 4-5. Post-Project Habitat Types at the New Tide Gate Structure................................. 4-49 Figure 4-6. Level A and B Impact Thresholds for Marine Mammals ....................................... 4-62 Figure 4-7. Comparison of Aerial Imagery during Low and High Tides................................... 4-96 Figure 4-8. Recreational Opportunities in Project Vicinity ..................................................... 4-119 Figure 4-9. Trail Detours Outside Active Construction Period .............................................. 4-121 Figure 4-10. Trail Detours During Active Construction Period .............................................. 4-122 Tables Table 1-1. Summary of Applicable Regulatory Requirements ................................................... 1-3 Table 2-1. Import Materials ........................................................................................................ 2-9 Table 2-2. Disposal Materials .................................................................................................. 2-10 Table 2-3. List of Equipment and Estimated Operation ........................................................... 2-15 Table 2-4. Best Management Practices .................................................................................. 2-19 Table 4-1. County and City Policies Related to Aesthetics ....................................................... 4-4 Table 4-2. Thresholds of Significance for Criteria Air Pollutants/Precursors ........................... 4-11 Table 4-3. Construction Emissions without BMPs Incorporated by Calendar Year ................. 4-14 Table 4-4. Palo Alto Comprehensive Plan Policies Related to Biological Resources ............. 4-21 Table 4-5. Palo Alto Baylands Master Plan Policies Relevant to Biological Resources .......... 4-22 Table 4-6. Special-Status Plants with Potential to Occur in the Study Area ............................ 4-31 Table 5-7. Special-Status Animal Species with Potential to Occur in the Study Area ............. 4-36 Table 4-8. Land Cover Type Conversions within the Project Area .......................................... 4-47 Table 4-9. Interim Injury Criteria for Fish ................................................................................. 4-57 Table 4-10. NMFS In-water Level A Acoustic Thresholds (PTS Onset) .................................. 4-59 Table 4-11. NMFS Current In-Air Level A and Level B Acoustic Thresholds .......................... 4-59 Table 4-12. Hydroacoustic Assessment for Construction