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. 404 WEST FREMONT STREET WKA No. 1628.09 August 31,2001 Page 3 i { Quarterly Report,to have over one and one-half feet of floating hydrocarbons on the water. The RESNA quarterly report also indicates ground water flow direction beneath the western portion pq of the property is to the north with a gradient of 0.003 ft/ft. Ed Geology The Geologic Map of the San Francisco--San Tose Quadrangle (Wagner et al, 1991) shows the site vicinity underlain by Pleistocene alluvial sediments of the Modesto Formation. Deposits of the Modesto Formation are described as unconsolidated, tan and light gray gravelly sand, silt, < � and clay(Helley and Harwood, 1985). The soils observed during the tank removal and -� subsequent site investigations have been consistent with that description. Soils beneath the site consist of clay and clayey silt at the surface and show increasing grain size with depth. The clays and silts generally grade to silty sand at about 19 to 20 feet bgs. The f' downward-coarsening trend continues within the sands, with some borings (e.g.,MWI and MW4) grading from silty fine sand at about 20 feet bgs to gravelly sand or sandy gravel at about 30 to 36 feet bgs. These relatively coarse-grained deposits rest on a layer of stiff clay that was encountered at 34 to 39 feet bgs in five borings at the site (MWI, MW2, MW3,MW4, and VEW1). Where encountered, the clay persisted to 40 feet bgs, the maximum depth explored beneath the site. Similar conditions were reported beneath the Chase Chevrolet site, located on the east side of Van Buren Street. At that site, "lean clay was found from 36-38 feet below grade E==1 to the bottom of the borings at approximately 46 feet." (RESNA Industries, 1991). Groundwater The site lies within the San Joaquin Valley Ground Water Basin(California Department of Water Resources, 1986). In the vicinity of the site, ground water generally flows in an easterly or northeasterly direction,based on the Ground Water Elevation Contour Maps published by San `J Joaquin Flood Control and Water Conservation District(maps for Fall 1996, Spring 1997, Fall 1997, Spring 1998, Fall 1998, and Spring 1999).