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,r f 2.2 Site History and Contaminants e It is understood that the site was a former gasoline service station,which.-'was previously owned and operated by past property owners. Dorothy Sandberg,the current owner of the site, has never operated the site as a gasoline service station. In May 1998, two USTs (one3,5007gallon UST,tank identification f number 39-2528-02; and one 4000-gallon UST, tank identification number 39-2528-01)were removed from the site(Figure 2). �. Discolored soil was identified at the bottom of the tank excavation during the removal, and soil samples r } were collected to determine the level, if any, of total petroleum hydrocarbons(TPH). Analytical results it detected TPH ranging from 1,000 milligrams per kilogram (mg/kg)k to 1,500 mg/kg. The soil sample analysis quantified the hydrocarbon contamination as weathered diesel fuel. No gasoline or gasoline constituents were detected. The vertical and horizontal extent of petroleum hydrocarbon impact was not defined during the tank removals, therefore, a subsurface soil investigation was requested by the PHS- I I EHD - San Joaquin County. F 2.3 Site Geology I I Based on observations made during this investigation, on site soils include clayey to sandy silt(from approximately 5 to 20 feet below ground surface [bgs]), and sand and silty clay(from 20 to 30 feet bgs.) The soil density ranges from loose to very dense and moisture ranges from moist to slightly moist. The maximum depth explored during this investigation was 31-feet bgsGroundwater reportedly exists at a 31 ' depth of approximately 110 to 120 feet bgs(PHS-EHD- San Joaquin County.) i' 3.0 SAMPLING METHODS iIR , The following sections describe the methods used during the subsurface soil investigation at the site. �l E 3.1 Soil Boring Locations i ;} The USTs were removed from the west side of the property adjacent to Bonham Street within an asphalt i" paved parking area. Based on the former location and orientation of the tanks, three soil borings were located within, and on the periphery of the tank excavation(Figure 3). 3 i$ :E