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r <br /> 2.0 BACKGROUND <br />' In late October and early November, 1990 ESE drilled five bonngs and converted three to <br /> ground water monitoring wells (MW-1, MW-2 and MW-3) within and near the former <br /> excavation (Figure 1). Soil boring B-2Y was terminated at an approximate depth of 15 feet <br /> below ground surface (bgs) due to auger refusal by construction debris which may represent <br /> fragments of backfill material or remnants of the grade fill seal A composite grab sample <br /> of soil cuttings reported to contain asphalt chips was collected at the direction of a <br /> ' PHS/EHD representative and analyzed Concentration of Total Petroleum Hydrocarbons <br /> as Diesel (TPH-D) was reported at 110 milligrams per Kilogram (mg/Kg) in this soil <br /> sample. The analytical results of soil samples collected from soil borings MW-1, MW-2, and <br /> MW-3 (later converted to ground water monitonng wells) and B-2X reported concentrations <br /> of TPH-D less than 4 mg/Kg. <br /> MThe three ground water monitoring wells were momtored quarterly for five quarters prior <br /> to the current investigation. Quarterly monitoring results have shown Benzene, Toluene, <br /> Ethylbenzene, and Xylenes (BTEX) concentrations well below California Action Levels but <br /> for one exception. In August 1991 benzene was found at the California Action Level in <br /> ' MW-2 but was not confirmed during the next quarterly monitoring. This was the only <br /> occurrence of benzene in any quarter monitored. Based on these results, ESE requested <br /> ' site closure from the PHS/EHD on two separate occasions. Site closure was denied because <br /> of the detectable hydrocarbons in the ground water. <br /> r <br /> i <br /> 1 <br /> F \5M004\ADDSAssi?RFT 3 <br /> 1 <br />