ARCHIVED REPORTS - GROUNDWATER MONITORING WELL INSTALLATION AND LIMITED SOIL SAMPLING

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' . h4 KLEINFELDER 7 CONCLUSIONS AND RECOMMENDATIONS 7.1. CONCLUSIONS Kleinfelder collected and analyzed soil samples from varying depths at the subject site. The soil samples collected and analyzed from across the site showed relatively higher concentrations of ' lead on the eastern half of the site versus the western half of the site. It appears that the bulk of the lead contamination is contained to the eastern portion of the site. ' The soil sample analyses included TTLC-lead for the soil samples collected at discrete shallow depths from near the concrete pad and across the site and subsequent STLC-lead on sample results exhibiting a concentration greater than 10 x's the STLC value of 5 mg/1 (50 ppm). A total of 24 ' discrete samples were analyzed for TTLC-lead from varying depths of 1 to 2-feet and 5-feet. The 5-foot sample was collected but not analyzed pending the results of the shallow samples at locations B-7 through B-18. The results of the shallow soil samples showed concentrations of TTLC-lead ranging from non-detectable (<10 mg/kg) to 1,200 mg/kg. Half of the shallow soil samples (6 out of 12) collected near the concrete pad showed concentrations requiring an STLC- lead analysis and 58% of the soil samples (7 out of 12) collected from across the site showed ' concentrations requiring an STLC-lead analysis. The STLC analyses showed 9 of the 13 samples analyzed for STLCs to display concentrations ' greater 5 mg/l. As shown in Table 7 in the previous section of this report, the highest concentration of lead contamination occurs near the central portion of the site near the concrete pad to a depth up to approximately 6 feet below the ground surface. Other areas of the site with ' noted high concentrations of lead are on the western side of the site on parcel 16 at boring location B-17, and throughout the eastern portion of the site. (parcels 10, 11, 12, and 13) to at least the ' analyzed shallow depth of 1-foot below the ground surface. The soil samples collected and analyzed from near the concrete pad appeared to show decreasing ' concentrations of lead with depth in 5 out of the 6 sample locations with concentrations decreasing to non-detectable levels at or above the laboratory reporting limit in 3 out of the 5. In only one location (B-6) the concentration increased with depth from a non-detectable result at 2- feet to a concentration of 110 mg/kg result at 5-feet. Soil samples analyzed from the 1-Foot depths from across a majority the site indicate lead ' contamination to at least that depth. Near the perimeter of the concrete pad located near parcels 11, 12, and 13 an area to a depth of at least 3-1/2 feet has been characterized as being impacted with lead. The 3-1/2 depth was chosen as an affected depth because of the previous WHF report ' results showing STLC concentrations greater than 5 mg/l and Kleinfelder's results to a depth of at least 2 feet. The most acutely affected areas of the site with lead contamination appears to be centrally located near the south side of the concrete pad where contamination was shown to ' 42162.E01/ST04R854 Page 19 of 22 Copyright 2004,Kleinfelder,Inc. July 1,2004