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Soil and Groundwater Investigation Report <br /> Mountain House Development Site#6 July 2008 <br /> • Area 2 is located at the central portion of the site. This area consists of boring locations SB-5, <br /> SB-13, SB-14, SB-16, and SB-18; and <br /> • Area 3 is located in the southeastern portion of the site. This area consists of boring locations <br /> SB-21 and SB-22. <br /> Affected soil in Area lwas observed in borings SB-9, SB-10, SB-11, and SB-15 between 7 and 35 feet <br /> bgs. Samples submitted to Lancaster exhibited affected soil between 16 to 26 feet bgs. Vertical profile <br /> samples were collected from SB-9, SB-10, SB-11, and SB-15 at depths ranging from 35 to 39.5 feet bgs. <br /> Laboratory analytical results from these samples were below ESLs and PRGs, indicating that the lower <br /> extent of affected soil was determined in this area. <br /> Affected soil in Area 2 was observed in borings SB-5, SB-13, SB-14, SB-16, and SB-18 between 13 and <br /> 25.5 feet bgs. Samples submitted to Lancaster exhibited affected soil between 13 to 23.5 feet bgs. <br /> Vertical profile samples were collected from SB-5, SB-13, SB-14, SB-16, and SB-18 at depths ranging <br /> from 24 to 33.5 feet bgs. Laboratory analytical results from these samples were below ESLs and PRGs, <br /> indicating that the lower extent of affected soil was determined in this area. <br /> Affected soil in Area 3 was observed in borings SB-21 and SB-22 between 4 and 26 feet bgs. Samples <br /> submitted to Lancaster exhibited affected soil between 5 to 25 feet bgs. Vertical profile samples were <br /> collected from SB-21 and SB-22 at 27.5 and 31.5 feet bgs,respectively. Laboratory analytical results <br /> from these samples were below ESLs and PRGs, indicating that the lower extent of affected soil was <br /> determined in this area. <br /> The depth of affected soil in all three areas was deeper than previously encountered at the site. <br /> 5.2 EXTENT OF AFFECTED GROUNDWATER <br /> Groundwater analytical results were compared to the lowest,most conservative WQO and ESL <br /> concentrations for delineation purposes. Groundwater analytical results are summarized in Tables 4 <br /> and 5. The comparison indicated that soil sample analytical results obtained during this investigation <br /> were less than WQOs and ESLs screening levels,with the following exceptions: <br /> • TPHd were detected above the ESL and/or WQO screening levels in three soil borings. The <br /> highest TPHd concentration was detected in boring SB-15 at 30 feet bgs(1,000 µg/L); and <br /> • Low concentrations of PAHs were detected above the ESL and/or WQO levels were detected in <br /> two borings. The highest PAH concentration was detected in boring SB-2 (dibenz[a,h]anthracene <br /> at 0.0064 gg/L). <br /> COC concentrations in soil that exceeded ESLs and/or WQOs are shown on Figure 3. The groundwater <br /> analytical reports are included in Appendix E as Appendix E.2. <br /> 5.2.1 Distribution in Groundwater <br /> The site has three distinct areas of affected groundwater, as shown on Figure 3: <br /> • Area 1 is located at the northwestern portion of the site. This area consists of boring locations <br /> SB-9, SB-10, SB-11,and SB-15; <br /> • Area 2 is located at the central portion of the site. This area consists of boring locations SB-5, <br /> SB-7, SB-13, SB-14, SB-16, and SB-18; and <br /> • Area 3 is located in the southeastern portion of the site. This area consists of boring locations <br /> SB-1, SB-2, SB-3, and SB-22. <br /> Depth-discrete vertical profile samples were collected in Area 1 from borings SB-10 and SB-15 at 35 and <br /> 30 feet bgs,respectively. Laboratory analytical results from the sample collected from SB-10 were below <br /> ESLs and WQOs,indicating that the lower extent of affected groundwater was determined in this area. <br /> From Science to Solutions <br />