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•r/ Y A total of ten borings were drilled at the site with borings one through nine being completed in the initial soils investigation phase. Boring number 10 was drilled during the installation of groundwater monitoring wells and was used to delineate the north- ern extent of the soils contamination. Locations of the borings are shown in Figure 3 . The area in this diagram is denoted as the inset in Figure 2. Each borehole was sealed with bentonite pellets through the depth of the standing water column. The remaining portion of the hole was filled with a neat cement grout. Permits were obtained for the drilling of all soil borings and abandonment of each boring was witnessed by a representative of the San Joaquin Local Health District. 2.2 Results of Laboratory and Field Analysis Laboratory analyses reports for the soil samples are given in Appen- dix A. The data reveals high levels of contamination at various sam- pling intervals of borehole 3 . The reasons for this are two-fold. The high levels of diesel and petroleum oil found in sample 3A, 2300 and 5400 ppm respectively, are most likely present as a result of spillage from the fuel island located just north of the sample point. The fluid has leaked into the substrate via cracks in the concrete slab which covers the ground in this area. High concen- trations of these same two constituents, 3300 and 5000 ppm respect- ively, were also found in sample 3D which was taken at a depth of 20 to 21.5 feet. This depth is just beneath the base of the exca- vation which lies at 18 ft. The existence of contamination at this level is the result of leakage from the tanks on their northern facing flanks or in the associated piping that ran northwards to- wards the fuel island. In the remainder of the boreholes, detectable levels of contamina- tion were found in only 3 locations in the unsaturated substrate. Boring 10 contained 7 ppm of motor oil at the 5 to 6.5 ft. interval while 2.7 ppm of diesel were found in boring nine at 20 to 21.5 ft. Low levels of hydrocarbon contamination were also revealed in bor- ing 7. Moderate levels of hydrocarbon contamination were found in soil samples taken at the water table (30-31.5 ft. ) . This data is w considered to be representative of groundwater conditions and is not addressed in the soils investigation or the implementation of remedial actions. Figures 3 through 8 illustrate results of field screening and labor- atory analyses of samples obtained from the boreholes for each sample interval. The figures do not contain data for ethyl benzene which was not detected by any of the analyses performed at the lab. .. (4)