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' 2 3 2 Surrounding Land Use The surrounding area is comprised primarily of commercial property to the north, south, and east of the Site The nearest residential property is located approximately 500 feet west of the Site The San Joaquin Channel is located approximately 27 miles to the west and Calaveras River approximately nine iniles to the south Current zoning in the area is for commercial and residential land use 2.4 Geology 2 4 1 Regional Geologvv ' The Site is located in the San Joaquin Valley of the Central Valley geomorphic province Geologically, the Central Valley is a large elongate northwest-trending asymmetric structural trough that has been filled with a thick sequence of sediments ranging in age from Jurassic to Recent The ' basin has a regional southward tilt, wluch is interrupted by two significant cross-valley faults The northernmost fault, the Stockton fault, is the boundary used by most geologists to separate the Central Valley into the Sacramento and San Joaquin subbasins, (Thrifty, 1997) Holocene age ' floodplain deposits extend from ground surface to a maximum depth of approximately 100 feet below the Site Oligocene to Holocene age alluvial deposits he below the younger floodbasin 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 composed of shale, sandstone and conglomerate Crystalline bedrock underlies the sedimentary formations (Thrifty, 1995) 2 4 2 Site Geology ' To aid in interpretation of subsurface lithology, numerous soil borings have been advanced The boring logs recorded during the drilling of these bonngs provide a description of the lithologic sediment underlying the Site The boring log information was used to construct two geologic cross-sections of the Site A plan view of the Site, showing the location of the geologic cross-sections is included as Figure 13. Cross-Sections A A' and B-B' are provided as Figures 14 and 15 Previous subsurface investigations conducted by others encountered interbedded clayey silts and silty clays to the north at approximate depth of 53 feet bgs From north to south previous investigations encountered a continuous poorly sorted sand Iayer starting from 5 feet bgs and ending at a maximum depth of 25 feet bgs Interbedded clayey silts and silty clays were encountered as ' shallow as 12 feet bgs and as deep as 53 feet bgs from(north to south and east to west) the USTs From approximately 42 feet to the maximum depth investigated of 73 feet bgs, soils consist of poorly-sorted sand and silty sand ' 2.5 Regional and Site Hydrogeology The deposits containing fresh groundwater are principally uncemented continental deposits of Pliocene to Recent age that extend to depths ranging from less than 100 to more than 3,500 feet bgs Groundwater occurs under both confined and unconfined conditions in the Central Valley Recharge 1 A.11528J1 ASA