Appendix G Water Quality

GNOSS FIELD AIRPORT ENVIRONMENTAL IMPACT STATEMENT FINAL APPENDIX G WATER QUALITY This appendix contains the Water Quality Technical Report prepared for the Environmental Impact Statement and Environmental Impact Report. Landrum & Brown Appendix G – Water Quality June 2014 Page G-1 GNOSS FIELD AIRPORT ENVIRONMENTAL IMPACT STATEMENT FINAL THIS PAGE INTENTIONALLY LEFT BLANK Landrum & Brown Appendix G – Water Quality June 2014 Page G-2 Water Quality Technical Report Gnoss Field Airport Marin County, California Prepared for: Landrum & Brown, Incorporated November 20, 2009 Revised October 12, 2010 Submitted by: 2010 Page G-3 Table of Contents 1.0 Introduction ............................................................................................................. 1 2.0 Regulatory Framework .......................................................................................... 2 2.1 Federal Regulations ............................................................................................................. 2 2.1.1 Federal Clean Water Act ........................................................................................................... 2 2.1.2 Federal Aviation Administration Order 1050.1E, Environmental Impacts: Policies and Procedures .......................................................................................................................... 3 2.1.3 Federal Safe Water Drinking Act ............................................................................................... 4 2.1.4 Fish and Wildlife Coordination Act of 1980 .............................................................................. 4 2.2 State Regulations ................................................................................................................. 4 2.2.1 State Water Resources Control Board ....................................................................................... 4 2.3 Local Regulations ................................................................................................................ 7 2.3.1 Marin County ............................................................................................................................. 7 3.0 Environmental Setting .......................................................................................... 10 3.1 Project Location ................................................................................................................ 10 3.2 Site History ........................................................................................................................ 10 3.3 Land Use ........................................................................................................................... 10 3.4 Project Description ............................................................................................................ 10 3.5 Physical Features ............................................................................................................... 11 3.5.1 Topography .............................................................................................................................. 11 3.5.2 Soils ......................................................................................................................................... 11 3.5.3 Regional Hydrology ................................................................................................................. 11 3.5.4 Local Hydrology ...................................................................................................................... 11 3.5.5 Precipitation and Climate ........................................................................................................ 14 4.0 Water Quality Assessment Methodology ............................................................ 15 4.1 Methodology ..................................................................................................................... 15 4.2 Water Quality Parameters of Concern ............................................................................... 16 4.2.1 pH ......................................................................................................................................... 17 4.2.2 Specific Conductance ............................................................................................................... 17 4.2.3 Oil and Grease ......................................................................................................................... 17 4.2.4 Total Organic Carbon .............................................................................................................. 18 4.2.5 Biological Oxygen Demand ..................................................................................................... 19 4.2.6 Chemical Oxygen Demand ....................................................................................................... 19 4.2.7 Suspended Sediment ................................................................................................................. 19 4.2.8 Nutrients ................................................................................................................................... 20 4.2.9 Trace Metals ............................................................................................................................ 21 4.2.10 Pathogens ................................................................................................................................. 23 4.2.11 Pesticides ................................................................................................................................. 23 4.3 Airport Operations that May Affect Water Quality and Applicable Best Management Practices ............................................................................ 24 4.4 Water Quality Parameters of Concern Summary .............................................................. 26 4.5 Stormwater Pollutant Loads .............................................................................................. 28 4.5.1 The Simple Method................................................................................................................... 28 5.0 Water Quality Existing Conditions (2008) ......................................................... 29 6.0 Environmental Consequences and Impacts ....................................................... 31 6.1 Alternative A – No Action ................................................................................................ 33 Gnoss Field Airport i Landrum and Brown, Inc. Water Quality Technical Report Foothill Associates © 2010 Page G-4 6.2 Alternative B ..................................................................................................................... 34 6.3 Alternative D ..................................................................................................................... 35 6.4 Conclusions ....................................................................................................................... 35 7.0 References .............................................................................................................. 36 List of Tables Table 1 — Beneficial Uses Pertinent to the Proposed Project .............................................5 Table 2 — Gnoss Field Airport Operations and Potential Storm Water Pollutants ..........24 Table 3 — Event Mean Concentrations for Stormwater Runoff by Land Use (mg/l) .......27 Table 4 — Gnoss Field Water Quality Pollutant Sampling Data ......................................29 Table 5 — Gnoss Field Existing Conditions (2008) – Estimated Average Annual ............. Pollutant Loads ................................................................................................30 Table 6 — Estimated Average Annual Pollutant Loads by Alternative ............................32 Table 7 — Estimated Annual Pollutant Loading Increase by Alternative Compared to ExistingConditions (2008) Pollutant Loading .................................................33 List of Figures Figure 1 — Site and Vicinity .............................................................................................39 Figure 2 — Soils ................................................................................................................40 Figure 3 — Local Drainage ...............................................................................................41 Figure 4 — Site Drainage ..................................................................................................42 List of Appendices Appendix A — Water Resources Gnoss Field Airport ii Landrum and Brown, Inc. Water Quality Technical Report Foothill Associates © 2010 Page G-5 1.0 INTRODUCTION This report presents detailed information on existing conditions (2008) related to water quality associated with implementation of the proposed Gnoss Field Airport Runway Extension Project (proposed project). This report provides data and analysis in support of the Environmental Impact Statement/ Environmental Impact Report (EIS/EIR) for the proposed project. This Water Quality Technical Report discusses the regulatory setting, describes existing water quality conditions (2008) for the project site and immediate vicinity, and analyzes three project alternatives, including the No Action Alternative (Alternative A), the Preferred Alternative [Proposed Project (Alternative B)] and Alternative D. This report also describes methodology used to assess

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