Final ELKHORN SLOUGH TIDAL MARSH RESTORATION PROJECT Existing Conditions Report Prepared for July 1, 2014 Elkhorn Slough Foundation and Elkhorn Slough National Estuarine Research Reserve Final Draft Elkhorn Slough Tidal Marsh Restoration Project Existing Conditions Report Prepared for July 1, 2014 Elkhorn Slough Foundation 550 Kearny Street Suite 800 San Francisco, CA 94108 415.262.2300 www.esassoc.com Los Angeles Oakland Orlando Palm Springs Petaluma Portland Sacramento San Diego Santa Cruz Seattle Tampa OUR COMMITMENT TO SUSTAINABILITY | ESA helps a variety of Woodland Hills public and private sector clients plan and prepare for climate change and emerging regulations that limit GHG emissions. ESA is a registered 211778.01 assessor with the California Climate Action Registry, a Climate Leader, and founding reporter for the Climate Registry. ESA is also a corporate member of the U.S. Green Building Council and the Business Council on Climate Change (BC3). Internally, ESA has adopted a Sustainability Vision and Policy Statement and a plan to reduce waste and energy within our operations. This document was produced using recycled paper. OUR COMMITMENT TO SUSTAINABILITY | ESA helps a variety of public and private sector clients plan and prepare for climate change and emerging regulations that limit GHG emissions. ESA is a registered assessor with the California Climate Action Registry, a Climate Leader, and founding reporter for the Climate Registry. ESA is also a corporate member of the U.S. Green Building Council and the Business Council on Climate Change (BC3). Internally, ESA has adopted a Sustainability Vision and Policy Statement and a plan to reduce waste and energy within our operations. This document was produced using recycled paper. Table of Contents 1 INTRODUCTION ......................................................................................................................................... 1 1.1 PROJECT BACKGROUND ..................................................................................................................................... 1 1.2 PROJECT GOALS AND APPROACH ......................................................................................................................... 2 1.3 PURPOSE OF THE EXISTING CONDITIONS REPORT ..................................................................................................... 2 2 GEOGRAPHIC SETTING AND LAND USE HISTORY ......................................................................................... 3 2.1 ELKHORN SLOUGH ............................................................................................................................................. 3 2.2 RESTORATION SITE ............................................................................................................................................ 3 2.2.1 Seal Bend Restoration Site ....................................................................................................................... 4 2.2.2 Minhoto‐Hester’s Restoration Site ........................................................................................................... 4 2.3 MINHOTO STOCKPILE AREA AND ADJACENT UPLANDS .............................................................................................. 5 3 TOPOGRAPHY, HYDROLOGY AND WATER QUALITY .................................................................................... 6 3.1 TOPOGRAPHY .................................................................................................................................................. 6 3.2 VEGETATION‐ELEVATION‐INUNDATION RELATIONSHIPS ............................................................................................ 7 3.3 HYDROLOGY ..................................................................................................................................................... 8 3.3.1 Tides ......................................................................................................................................................... 8 3.3.2 Watershed Characteristics ..................................................................................................................... 10 3.3.3 Surface Water Hydrology ....................................................................................................................... 10 3.3.4 Groundwater Hydrology ........................................................................................................................ 10 3.4 WATER QUALITY ............................................................................................................................................. 11 3.4.1 Temperature ......................................................................................................................................... 11 3.4.2 Salinity ................................................................................................................................................... 11 3.4.3 Dissolved Oxygen and Eutrophication ................................................................................................... 11 3.4.4 Nutrients ............................................................................................................................................... 12 3.4.5 Turbidity and Suspended Sediment ....................................................................................................... 13 3.4.6 Contaminants ........................................................................................................................................ 13 4 GEOLOGY AND SOILS .............................................................................................................................. 15 4.1 REGIONAL GEOLOGY AND SEISMICITY .................................................................................................................. 15 4.2 SURFICIAL GEOLOGIC DEPOSITS ......................................................................................................................... 16 4.3 SOILS ............................................................................................................................................................ 17 4.4 SEDIMENT QUALITY ......................................................................................................................................... 17 5 BIOLOGICAL AND ECOLOGICAL COMMUNITIES .......................................................................................... 20 5.1 BIOTIC HABITATS ............................................................................................................................................ 20 5.1.1 Subtidal/Aquatic .................................................................................................................................... 20 5.1.2 Intertidal Mudflat/Aquatic ..................................................................................................................... 24 5.1.3 Intertidal Salt Marsh .............................................................................................................................. 26 5.1.4 Diked Salt Marsh .................................................................................................................................... 28 5.1.5 Diked Brackish Marsh/Willow Thicket ................................................................................................... 29 5.1.6 Formerly Cultivated Field/Ruderal Grassland ........................................................................................ 30 Elkhorn Slough Tidal Marsh Restoration Project D120505 DRAFT Existing Conditions Report 1 July 1, 2014 5.1.7 Eucalyptus Grove ................................................................................................................................... 31 5.2 SPECIAL‐STATUS PLANT AND ANIMAL SPECIES ....................................................................................................... 31 5.2.1 Special‐status Plant Species and Sensitive Habitats .............................................................................. 32 5.2.2 Special‐status Animal Species ................................................................................................................ 34 6 CONCEPTUAL MODEL OF HABITAT RESTORATION ..................................................................................... 49 7 REPORT PREPARERS ................................................................................................................................. 51 8 REFERENCES ............................................................................................................................................. 52 PERSONAL COMMUNICATION ........................................................................................................................................ 62 List of Tables Table 1. Restoration Site Elevations Table 2. Tidal Datums Table 3. Soil Characteristics in Minhoto Marsh Table 4. Pajaro Bench and Minhoto Marsh Sediment Chemistry Table 5. Existing Biotic Habitats and Land Use Types Table 6. Special‐status Animal Species, Their Status, and Potential Occurrence at the Project Site List of Figures Figure 1. Regional Map Figure 2. Site Map Figure 3. 1854 US Coast Survey Map Figure 4. 1946 Aerial Photograph of Harbor Construction Figure 5. 1952 Aerial Photograph of Restoration Sites Figure 6. Topographic/Bathymetric Map Figure 7. Surveyed Habitat Elevations Figure 8. Regional Geology