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Mr.Jadi Singh January 24,2003 Job Number:LE02491 Page 4 r ground water depth below ground surface as 6.2 1,the lowest depth as 11.22 feet below the ground surface, and the flow direction as northwest. Drinking water wells and surface water are reported to be affected by the leak. ` Three monitoring wells on the subject property were abandoned on September 19, 1997,under the supervision of Fluor Daniel GTI. The April 16, 1998 report prepared by Fluor Daniel GTI states that MW 1 "historically has not contained petroleum hydrocarbons above detection limits," while MW2 and MW3 "have historically contained varying concentrations of petroleum hydrocarbons." .. The subject property was issued a no further action letter with regard to the underground tank release by EHD on May 7, 1998. 4.0 HYDROGEOLOGIC SETTING 4.1 Geology and Soils The surface geology at the site is shown on a geologic map mapped by Atwater(1982). The area is mapped as the Holocene age alluvial-floodplain deposits,undivided. The soil/sediment on the site was composed of an unconsolidated, medium dense,brown silty sand similar to the Lodi area silty sands located adjacent to the Mokelumne River. The geologic map indicates that a ` paleo-drainage exists approximately 400 feet north of the site. It is a remnant of a past creek which had meandered through the town of Thornton. .. The surface soils at the site are reported to be Sailboat silt loam(no. 234). The San Joaquin Soil Survey describes the soil as a very deep, somewhat poorly drained, nearly level soil on flood plains (USDA, 1990). It formed in alluvium derived from granitic rock sources. Permeability is moderately slow in the Sailboat silt loam. Neil O. Anderson&Associates drilled six shallow percolation test holes on November 21,2002 and November 21, 2003 and one 14-foot deep ground-water test hole. In addition,two double ring infiltrometer tests were performed on the surface soils to measure the infiltration rate(Plate 1). A deep ground water/soil boring was drilled to a depth of 14 feet. Several shallow percolation _ test borings ranging from 1 foot to 3 feet deep were also drilled on the property. The following soil log represents the 14 foot deep ground water/soil boring and is representative of the soil ?OF R1 s