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5.0 CONCLUSIONS AND RECOMMENDATIONS <br /> 1 5.1 CONCLUSIONS <br /> Dames & Moore offers the following conclusions: <br /> • Copper and lead were detected in Parcel III near surface soil at concentrations exceeding <br /> Vtheir respective STLC. The distribution of copper appears limited to the near surface soil <br /> along the conveyor system easement and the former concentrate stockpile area. This <br /> distribution of copper is probably attributable to the copper concentrate formerly <br /> stockpiled on and distributed from on-site. The distribution of lead appears to be limited <br /> to a single location along the easement; <br /> • Detectable levels of pesticides and PCBs were not detected in soil samples collected from <br /> Parcel III; <br /> r} • Relatively low concentrations of TRPH were detected in both near surface and capillary <br /> fringe soil samples from Parcel M. TRPH testing method 418.1 is a quantitative method <br /> which screens a wide carbon chain range and does not differentiate the type of <br /> hydrocarbons present. The detections of TRPH may be due to residual coal or petroleum <br /> coke in the samples or migration from an off-site source. TRPH was not detected in <br /> groundwater. Tank farms located to the west and south of the site are known to have <br /> impacted groundwater (Dames & Moore, 1991) and may be a source of TRPH in <br /> groundwater. <br /> • Acetone was the only VOC detected in Parcel IR soil. Acetone was detected in the <br /> rRi capillary fringe in the boring for monitoring well MW-4, No VOCs were detected in <br /> groundwater. Given the absence of acetone in near surface soils, the detections of <br /> acetone may be the result of the migration of impacted groundwater at some time in the <br /> past or from another source; <br /> • Soil samples collected from Parcel III do not appear to be significantly affected by <br /> "1 SVOCs. Di-n-Butyl Phthalate was detected in both laboratory QA/QC and Parcel III soil <br /> samples. Therefore, detections of this compound are likely due to laboratory error. <br /> Very low concentrations of aliphatic compounds common to the wood treating industry <br /> „y were detected in the near surface soils from MW-4. However, there is no suspect on-site <br /> J source for these compounds. These detections may be due to treated wood fragments <br /> potentially present in the fill. <br /> • Sulphur and sulfate exist near regional background levels in Parcel III soil. Sulphur and <br /> sulfate concentrations appear to decrease with depth; <br /> • Arsenic was detected above the MCL in groundwater samples from MW-1 and MW-4; <br /> • Pesticides and PCBs were not detected in groundwater samples collected from Parcel III; <br /> . SAC28.013 <br /> 20 December 20, 1991 <br /> ,.'� LP,9P%�< <[., \¢,•r IRF <br />