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LEEOSHILL•HERKENHOFF, INC. <br /> 4.3 Source Identification Results <br /> ' As discussed in Section 3.1, to further investigate and identify contaminant <br /> sources, soil samples were collected under the three dry-cleaning establish- <br /> ments and underneath five sewer lines. As presented on Table 4.1, the <br /> results indicate that the soil beneath all three dry cleaning establishments <br /> contained detectable concentrations of PCE. At two of the sites, Finest <br /> Care Cleaners and the former Norge Cleaners, the concentration of PCE was <br /> ' low, non-detect to 2.82 mg/kg at the former Norge site and non-detect to <br /> 0.36 mg/kg at Finest Care. PCE concentrations at Village Cleaners were <br /> higher and ranged from 0.22 mg/kg to 8.4 mg/kg. TICE was not detected in any <br /> ' sample. <br /> Soil sampling under the sewer lines also indicated the low level presence of <br /> PCE in soil beneath certain sewer lines. The source of this contamination <br /> ' is leakage through the non-water-tight sewer joints. Table 4.2 presents a <br /> summary of the soil sampling beneath the sewer lines. TCE was not detected <br /> in any of the soil samples. The individual laboratory analysis are provided <br /> in Appendix C. <br /> It should be noted that soil samples collected beneath the sewer lines which <br /> ' had not been pressure grouted were noticably moist, compared to samples <br /> collected beneath pressure grouted lines, such as between MW#4 and <br /> Gettysburg Place, which was dry. <br /> Evaluation of the soil material collected during sewer soil sampling and <br /> installation of the monitoring wells indicated a forty-foot layer of silt or <br /> sandy silt overlaying an upper water bearing sand layer. The permeability <br /> (vertical movement) of water through silt or sandy silt is relatively moder- <br /> ate, roughly two orders of magnitude slower than through a sand. Therefore, <br /> once PCE/TCE contaminated water leaked through joints in the sewer line, it <br /> ' migrated to the upper sand layer and water table, before migrating <br /> laterally. <br /> Soil samples were also collected at five-foot intervals during the construc- <br /> tion of monitoring well #4. Samples at depths of 35, 45, and 70 feet were <br /> analyzed in accordance with EPA Method No. 8010. The depth to water is <br /> approximately 45 feet but there was a 10-foot layer of slightly moist soil <br /> ' from a depth of 35 to 45 feet. Laboratory analysis of these three samples <br /> indicated that only the 45 foot sample contained detectable levels of PCE <br /> (0.12 mg/kg) . Neither the moist sample from a depth of 35 feet, nor the <br /> deeper sample from 70 feet contained detectable levels of PCE or TCE <br /> ' contamination. This data supports the conclusion that the contamination is <br /> restricted mainly to the upper water-bearing zone and has not migrated <br /> naturally thorugh the existing geologic formations into deeper stratas. <br /> ' Individual laboratory analysis provided in Appendix C. <br /> The final work in the source identification phase was to collect raw sewage <br /> ' samples to insure that the sewer lines were no longer a continuing source. <br /> Six samples were collected from five on-site manholes and tested in <br /> accordance with EPA Method No. 601 (purgeable halocarbons) . Five of the six <br /> ' 4-3 <br />