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1 <br /> ' 3.0 SITE BACKGROUND <br /> ' <br /> Ij Tank Removal and Excavation <br /> On March 31, 1989, an underground diesel tank was removed from the site Soil contamination <br /> was noted in the sidewalls of the excavation and oily water was observed in the tank pit <br /> 1 (RESNAIWaterWork, 1990) Soil samples were collected from each wall of the pit (Figure 2) <br /> Groundwater was encountered in the tank pit at a depth of 10 feet below ground surface (bgs) <br /> The soil samples contained elevated concentrations of diesel constituents (Table 1) Due to the <br /> elevated concentrations of diesel constituents in the soil and the presence of groundwater in the <br /> 1 pit, PHS/EHD required further assessment of soil and groundwater contamination at the site <br /> While the excavation was open, 1,500 gallons of the oily water was removed from the pit by I T <br /> 1 Corporation (RESNA/WaterWork, 1990) Approximately 99% of the liquid was estimated to be <br /> water, and 1% (15 gallons) was thought to be product The oily water was transported by I T <br /> 1 Corporation to a refinery in Richmond, California for reprocessing <br /> 3_2 Assessment of Soil Contamination <br /> To attempt to define the extent of residual soil contamination on January 18, 1990, four soil <br /> borings (MW1, B2, B3, and B4) were advanced to depths ranging from 7 to 19 5 feet bgs <br /> (RESNA 1993) One boring was completed as a monitoring well, MW-1 (Figure 2) Descriptions <br /> of the material encountered and field screerung readings are presented on the stratigraphic logs in <br /> 1 Appendix V Soil samples collected from boreholes B2, B3, and B4 near the top of the capillary <br /> fringe at 6 0 to 6 5 feet bgs were analyzed for benzene, ethylbenzene, toluene, and xylenes <br />' (BTEX), and total petroleum hydrocarbons as diesel (TPHd) Petroleum hydrocarbon analytes <br /> were not present in the soil samples collected from the borings (Table 1) <br /> 1 On January 2 1991 two eight-inch soil borings were drilled and completed as groundwater <br /> 1 monitoring wells MW2 and MW3 (RESNA 1993) The borings were completed to a depth of <br /> approximately 23 feet bgs Descriptions of the material encountered and field screening readings <br /> are presented on the stratigraphic logs in Appendix V Capillary fringe soil samples were <br />' collected at six feet bgs and analyzed for BTEX and TPHd No petroleum hydrocarbon <br /> constituents were detected in the samples (Table 1) <br /> w 1967311reports\Ciosure doe 2 <br /> 1 <br /> SMTH <br />