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a (maximum of 120 milligrams per kilogram,[mglkg]TPHg)were detected along the west side of the excavation, beneath Tank#4. A total of 9 soil samples were collected by Canonie Environmental about every 20 linear feet along the pipeline at a depth of approximately 3 feet bgs. Soils beneath the dispenser were also sampled. Soils beneath the pipeline and dispenser were described by PHS/EHD as"loam and'�rock,""red," "black,"and"gray clay,"and"adobe clay with sand." Gray discolored soil and petroleum product odor were reported in the pipeline sample nearest the dispenser and in the sample beneath the dispenser itself. PHCs were detected in four of nine samples collected along the pipeline. Trace amounts of toluene,xylene, and ethyl benzene were detected in the sample approximately 120 feet west of the former tanks. Higher levels of PHCs,including 0.55 mg/kg benzene and as much as 140 mg/kg TPH&were detected near and beneath the former dispenser island where discolored soil and petroleum odors were detected during the pipeline removal. 2.2.2 Initial Subsurface Investigation Analytical results indicated no PHCs were detected in soil samples collected near the former.USTs in borings B5-1 through B5-3. However, the groundwater-sample collected from boring B5-1, along the eastern side of the former UST excavation; contained BTEX constituents and 4,2 milligrams per liter (mg/9) TPHg. Trace amounts of benzene (0.005 mg/kg) and to'oluene (up to 0.015 mg/kg)were detected in soil samples collected in boring B5-5 near the former dispenser area. No PHCs were detected in the soil samples collected in boring B54. Groundwater samples collected from borings B54 and B5-5 contained BTEX constituents(up to 0.46 mg/9 xylenes and 0.03 5 mg/9 benzene) and up to 1.1 mg/Q TPHg. Total lead was detected at concentrations ranging from 5.8 to 12 mg/kg in soil samples from each of the five borings drilled at the site. No lead was detected in the groundwater samples. These lead concentrations were found to be within background levels for the area. 2.3 GEOLOGIC AND HYDROLOGIC CHARACTERISTICS The site is located on the delta of the San Joaquin River, approximately 2 miles east of the confluence of the San Joaquin and Calaveras Rivers. The subsurface geology consists of a thick sequence of alluvial deposits of late Tertiary to Holocene Age, overlying sedimentary rocks of Cretaceous to Tertiary age, which in turn overlie crystalline basement rocks (Bartow and Nilsen, 1990). Data from nearby studies within the Port area indicate a soil profile to a depth of about 20 feet bgs comprised of interbedded sands and clays, mostly under reduced conditions(Sierra-Pacific Groundwater Consultants[SPGC], 1994). Lithologic data from boring B5-1 indicatesthe lithology in the vicinity of the former USTs comprises mostly fine-to very fine-grained sand and silty sand to a depth of about 17 feet bgs, with silt and clay predominant from about 17 to 2&!feet bgs, the �s 3 PHILIP P. Ross, R.G.