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5.0 CONCLUSIONS AND RECOMMENDATIONS <br />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 />their 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 />Relatively low concentrations of TRPH were detected in both near surface and capillary <br />fringe soil samples from Parcel III. 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 III soil. Acetone was detected in the <br />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 />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 />were detected in the near surface soils from MW-4. However, there is no suspect on-site <br />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 HI; <br />SAC28.013 December 20, 1991 <br />20 <br />1DA1,IF.S & 1\4(..)ORI: