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Permit to Close," contained unleaded gasoline. A dispenser was located a few feet southwest of the tank. No information is available as to the age of the tank. The tank and associated piping were removed on April 28, 1993 by Jim Thorpe Oil, Inc., under permit from PHS/EHD. The PHS/EHD inspection report indicated that the tank was in "good" condition, with no visible holes and a small amount of corrosion. Approximately 5 yards of soil were excavated with the tank to a depth of about 5 feet below ground surface `- (bgs). Excavated soils were stockpiled just north of the excavation. Soil samples were collected by GeoAnalytical Laboratories from two locations in the stockpile (which were composited for analysis) and one sample was collected from the backhoe bucket, which removed soil from beneath the center of the tank excavation at a depth of about 8 feet bgs. No groundwater was encountered during excavation or sampling. Soils beneath the tank were reported by PHS/EHD to be "clay loam" and contained "odor and discoloration." f 2.2 SUMMARY OF PREVIOUS SITE CHARACTERIZATION WORK Soil samples collected from beneath the tank and the composite soil sample from the stockpile were submitted to GeoAnalytical Laboratories for analysis of total petroleum hydrocarbons as gasoline (TPHg) by EPA method 5030; benzene, toluene, ethyl benzene, and total xylenes (BTEX)by EPA method 8020, total lead by EPA method 7420; and ethylene dibromide(EDB) by the LUFT method. Analytical results (Table 1) indicated low levels of PHCs detected in both the stockpile and backhoe bucket samples, with no benzene or EDB detected in either sample, and only 28 mg/kg TPHg detected in the sample from beneath the tank. 2.3 GEOLOGIC AND HYDROLOGIC CHARACTERISTICS The subject 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 lateTertiary to Holocene Age, overlying sedimentary rocks of Cretaceous to Tertiary age, which in turn overlie crystalline basement rocks (Bartow and Nilsen, 1990). Based on data from nearby studies within the Port area, the soil profile at the site to a depth of about 20 feet bgs consists of interbedded, sands and clays, mostly under reduced conditions (Sierra-Pacific Groundwater Consultants [SPDC], 1994). Data from nearby studies indicates that the current depth to groundwater in the vicinity ranges from about 5 to 10 feet bgs (SPGC, 1998, and EMCON, 1998). Seasonal fluctuations in the water table appear to range from about 3 to 5 feet, with some as much as 6 to 9 feet. Historically, water levels in this area have risen as much as 8 feet since 1994. Tank removal 2 gat ami usrarv.wP