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GeoHydrologic Consultants, Inc • 3.0 SITE CHARACTERIZATION DATA 3.1 Geology/Hydrogeology ' The Site is located in the San Joaquin Valley of the Central Valley geomorphic province Recently published geologic maps indicate that Holocene age flood-basin deposits extend from ground surface to a maximum depth of approximately 100 feet ground surface (bgs) Oligocene to Holocene age alluvial deposits lie below the younger flood-basin deposits to a maximum depth of approximately 3,500 feet bgs Continental and marine rocks of pre-Tertiary to Oligocene age underlie the alluvial deposits, and are comprised of shale, sandstone, and conglomerate Crystalline bedrock underlies the sedimentary formations Based on the drilling logs, sediments beneath the Site consist mostly of clay, slit, sandy silt, silty clay, sandy clay, and clayey silt from the surface to approximately 65-70 feet bgs At this depth layers of sand consisting of silty sand, fine to coarse sand, and gravelly sand were encountered interbedded with finer grained soils to a total depth of approximately 115 feet bgs Generalized geologic cross-sections for the Site are included as Figures 3A, 3B, and 3C for A-A', B-B', and C-C' respectively ' Groundwater was encountered at a depth of approximately 50 feet bgs in 1988 within the silty clay sediments Well MW-3 was installed to 50 feet bgs and wells MW-1 and MW-2 0 were installed to a depth of approximately 60 feet bgs Because only two wells contained significant quantities of water,the hydraulic gradient could not be measured at that time During drilling in November 1992, groundwater was encountered 80 feet bgs, indicating a significant drop in the local water table had occurred Because of this decrease in groundwater elevation, none of the shallow monitoring wells contained groundwater and only wells MW-3R, MW-4, MW-5, and MW-6 were available for groundwater monitoring The static groundwater level has continued to fluctuate between 1992 and ' present Results of quarterly monitoring show a steady rise of the water table through 1993 and 1994 The hydraulic gradient has generally been 0 001-0 003 feet per foot to the east through this period During drilling in 1995, groundwater was encountered at a depth of approximately 60 feet bgs The hydraulic gradient was measured to be about 0 003 feet per foot to the ' northeast During the 15'Quarter 2005, depth to groundwater beneath the Site ranged from 48 68 feet bgs in monitoring well MW-5 to 50 64 feet bgs in monitoring well MW-6 Groundwater was estimated to be flowing towards the northeast with an approximate gradient of 0 004 feet per foot • ' TOC 171 Pilot Study Page 2