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' hydrocarbon concentrations of 85 ppm of TPH as diesel. The contractor partially <br /> refilled the tank excavations with soils from the clean end of the excavation and <br /> ceased all additional remediation The remaining 50 cubic yards (approximate) of <br /> soil from the excavation was stockpiled on site <br /> 1:.2.2 Preliminary Site Investigation <br /> In February 1991, a preliminary soil and groundwater investigation was completed <br /> ' by SAI Soil hydrocarbons (TPH as diesel) were found to exist within the backfilled <br /> soils in the excavation at concentrations up to 680 mg/kg Borings around the <br /> perimeter (B-1, P-1, and P-2) of the excavation indicated maximum concentrations of <br /> ' TPH as diesel of 16 mg/kg and Benzene, Toluene, Ethyl Benzene and Xylenes <br /> (BTEX) were not detected at concentrations over the reporting limits Groundwater <br /> gradient based on well MW-1 and piezometers P-1 and P-2 was determined to be <br /> directed north 14" east with a magnitude of 0 37ft/100ft as described in the April 29, <br /> 1991 Report of Findings Groundwater samples from the monitoring well (MW-1) <br /> downgradient of the excavations indicated nondetectable concentrations of TPH as <br /> ' gasoline, TPH as diesel and BTEX. Based on those analytical results, the <br /> hydrocarbons were not expected to have migrated significantly beyond the <br /> boundaries of the previous excavation <br /> ' The soil and groundwater results from MW-1 adjacent to the former gasoline UST <br /> indicated nondetectable levels of hydrocarbons in the shallow soil and groundwater. <br /> ' 2.0 GENERAL SITE DESCRIPTION <br /> ' The USTs were located in rear of the DPC facility as shown on the Site Map <br /> (Figure 2). The yard restroom is adjacent to location of the removed USTs. The DPC <br /> yard surrounding the excavation is covered by a asphalt pad Soil stockpiles are <br /> located as shown on Figure 2 and are placed on plastic and are covered with plastic <br /> o <br /> The locations of the monitoringwell and two piezometers are as shown on Figure 3 <br /> Overhead power lines run to the north of threstroom Buried water and sewer <br /> ' lines also run to the plant from the restroom. <br /> Soils in the shallow zone consist of a silty sand with some areas of coarse sand and <br /> ' gravel. Water depth at the time of UST removal was approximately 12 feet but <br /> during the investigation the groundwater level was recorded at approximately 9 <br /> feet <br /> ' Groundwater gradient determined during the preliminary site investigation was <br /> directed north 14° east. <br /> 1 <br /> 2 <br /> ' BRUNSING ASSOCIATES, INC <br /> IMP <br />