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3.5.2 Soil Excavation ! In September and October 1995, approximately 8,406 cubic yards of soil were excavated from the vicinity of the former underground fuel storage tanks by Foothill Engineering The excavation was approximately 33 feet bgs and approximately 10 feet below the groundwater surface The limits of the excavation are shown on Figure 4 Confirmation soil samples were collected from the excavation sidewalls and bottom Samples collected from the north sidewall contained elevated concentrations of petroleum hydrocarbons One sample collected from each of the south, east, and west sidewalls also ' contained elevated concentrations of petroleum hydrocarbons Analytical results for the confirmation soil samples are summarized in Table 7 Excavation activities are summarized in the Foothill ! Engineering Soil Reme&ahon Excavation Report, dated January 31, 1996 With approval from PHS/EHD, the excavation was backfilled with clean material and compacted to the required 95% All damaged utilities were also replaced Wells MW-1 and MW-5 were destroyed during the excavation activities and were replaced with wells MW-1R, MW-5R, and MW-5R2 The excavation was then resurfaced with 6-inches of reinforced concrete ! 3.5.3 Stockpiled Soil Remediation On December 7, 1995, the stockpiled soil was sampled and analyzed for TPHg, BTEX, TPHd, total petroleum hydrocarbons as motor oil (TPH motor oil), and total petroleum hydrocarbons as kerosene (TPH kerosene) The samples were analyzed by Sherwood Labs, in Hilmar, California Samples contained low concentrations of TPH kerosene (18 ppm) and TPH motor oil (290), but contained no detectable concentrations of TPHd, TPHg, or BTEX Analytical results for the stockpiled soil sampling is contained in the Foothill Engineering Soil Remediation Excavation Report, dated January 31, 1996 On July 25, 1996, Foothill Engineering resampled the stockpiled soil A summary of the sample results are contained in the Foothill Engineering Report of Soil Samples, dated July 19, 1996 With the approval of the PHS/EHD in a letter dated September 18, 1996, the stockpiled soil was spread over the westerly section of the site to a depth of two feet 4.0 EXISTING CONDITIONS 4_1 Soil Conditions Soils encountered beneath the project site consist primarily of clayey silts and silty clays to approximately 45 feet below grade Apparent interbedded sand lenses were noted at various depths in soil borings SB-1, SB-2, SB-4, MW-1, MW-2, MW-3, MW4, and MW-6 Gravel was encountered in soil boring MW-2 Confirmation soil bonngs were not advanced following soil remediation activities at the site based on ' the analytical results obtained from the soil excavation bottom and sidewalls in October 1995 W\94331klomm doe 5 SAH