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C <br /> 1� <br /> gq <br /> f, <br /> Gravel fill removed from the pit was slightly stained, but <br /> hydrocarbon staining was not observed on the excavation <br /> xlls. A <br /> gr <br /> water samplevel collected <br /> co containing fel hydrocarbons lwasreturned to the <br /> The pea g <br /> excavation. <br /> Three monitoring wells (MW-1 through MW-3) were installed <br /> between August 12 and 14, 1987 (Figure 1-3). No petroleum <br /> hydrocarbons were detected in any of these borings during drilling <br /> activities nor in the groundwater fromm subsequent sampling of the <br /> wells. <br /> On March 12 and 15, 1988, eleven soil samples were collected from 0.5 <br /> to 1.0 foot below the concrete slab and analyzed for TPH. In a letter <br /> dated June 10, 1988 to Gordon Boggs of the Aenega Valley Regioted on <br /> Water Quality Control Board (CVRWQ ), <br /> to leave the concrete slab in the excavation based n g he analytical <br /> A <br /> results of the March 1988 soil sampling. <br /> the <br /> hydrocarbons, which had leaked from the tanks, had migrated <br /> om <br /> of <br /> laterally and downward <br /> tothethe <br /> southwesternthe <br /> corner the <br /> are <br /> contained in soil adjacent o <br /> excavation. <br /> Between July 26 and 28, 1988, WA removed 150 cubic yards of soil <br /> half-way along the southern and western walls of the excavation to a <br /> depth of 24 feet. <br /> In a proposal to the County dated November 22, 1988, Precision <br /> Instruments of Stockton requested to backfill a portion of the <br /> excavation. Upon approval in December 1988, the entire excavation <br /> was backfilled. <br /> Western GeGlogic Resources, Inc. In September and October 1989, <br /> another investigation was performed by WGR near the former tank <br /> locations. Six boreholes were drilled (B-10 through.B-15) from which <br /> soil samples were collected for chemical analysis (Figure 1-3). <br /> Groundwater was observed at 26.8 feet below grade. One of the <br /> boreholes(B Osa samples from) was completedwellsas a 4MW-Inonitoring through MW-4 we e <br /> Groundwater <br /> collected on October 3, 1989. <br /> The soil analytical results are summarized in Table 1-1. Total <br /> purge re petroleum m yin the soil samdrocarbons ples from 25 toerized as diesel <br /> 25 5 feet below <br /> #2, were detected only south <br /> grade in borings B-11, B-14 and B-15, located on the and 240nd ppm, <br /> side of the former tank locations, at 28 ppm, 120 pp <br /> respectively. Aromatic hydrocarbons including benzene, toluene, <br /> ._ 1-5 <br />