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WORK PLAN FOR GROUND WATER WELL INSTALLATION AND MONITORING PORT OF STOCKTON-ROUGH AND READY ISLAND,CALIFORNIA The USDA Soil Survey Geographic Database (SSURGO) provides geospatial data for surface soils throughout most of the state of California (USDA, 2012). The state is divided into polygon shapes containing specific data for soils in that area. The database provides lithologic descriptions in addition to depth to water data, soil chemistry, and physical parameters. Based on an evaluation of the SSURGO data for the site vicinity foundation soil types consists of Merritt silty clay/loam with characteristics shown below. Lowest Maximum Soil Measured Cation % % Annual Soil Number Soil Type Organic Clay Depth to Formation Exchange Matter y p -Capacity Water(cm) Silty 5 1-4 27-35 107 197 Merritt Clay/Loam 2.3.2 Local Hydrologic Setting Similar to other islands in the Delta, the surface of RRI is several feet below mean sea level (msl). A levee protects the island from the adjacent San Joaquin River, which is several feet above mean sea level. The surrounding San Joaquin River exerts hydrostatic pressure on the island's shallow ground water system. Consequently, unlike typical island ground water hydrology, the shallow ground water gradient in the Delta islands generally flows from the surrounding surface water towards the island's interior. The island ground surface is kept dry by a complex system of interior ground water drainage channels. The hydrologic setting that drains the shallow ground water also results in vertically upward ground water gradients. These island drainage channels direct water to the southwest where the water is then pumped into Burns Cutoff. Ground water levels presented in the SSURGO database indicate the highest annual ground water level for soils at the site is 107cm or 3.4 feet below ground surface (bgs). The depth to water is measured or estimated from open test pits or bore holes or based on prevailing water table conditions using soil morphology (e.g. presence of redoximorphic features) where water table monitoring data is unavailable. Ground water bearing materials in the vicinity of the proposed placement area typically occur at a depth of 10 feet (3.05 meters) bgs or greater, and ground water levels measured in adjacent ground water monitoring wells indicates that the highest seasonal piezometric ground water surface is approximately 4 feet (1.22 meter)bgs. September 2014 Environmental Risk Services P 4 Corporation