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e <br /> 4mkgkal lrechnics Inc. Page 5 <br /> Sinclair&Thompson Property <br /> Additional Soil Gas Survey Report <br /> June 18,2407 <br /> Iii Summary (highest results listed): <br /> • SG-7: Toluene 0.19 µg/L and m,p-xylenes 0.20 µg/L <br /> • SG-8: Toluene 0.13 µg/L, total xylenes 0.13 µg/L, and TPHg 7.6 µg2 <br /> • SG-9: Toluene 0.14 µg/L, total xylenes 0.19 µg/L, and TPHg 8.1 µg/L <br /> 3.0 RISK EVALUATION <br /> This section will compare the analytical results measured in the field with the Tier I Lookup <br /> Tables published in the CRWQCB-SFs: Screening for Environmental Concerns at Sites with <br /> Contaminated Soil and Groundwater, dated February 2005. <br /> 3 <br /> The Environmental Screening Levels (ESLs)-use the units ofµg/m and the laboratory results <br /> are recorded in units of µg/L. In order to compare the results of the field data with the ESLs <br /> in section 3.1 below, the field data were converted to µg/m3 (analytical results multiplied by <br /> 1;000-L/m3). <br /> f 3.1 Environmental Screening Levels <br /> The Shallow Soil Gas Screening Levels for Residential Land Use in Summary Table E of,the <br /> CRWQCB-SFs: Screening for Environmental Concerns at Sites with Contaminated Soil and <br /> Groundwater, dated.February 2005 was used for this evaluation. For the constituents of <br /> concern detected during the.additional soil gas investigation, the following thresholds are <br /> listed in the 2005 ESL table: <br /> • Benzene (85 µg/m3) <br /> • Ethyl benzene (420,000 µg/m) l <br /> • Toluene (63,000 µg/m3) <br /> • Xylenes (150,000 µg/m3) <br /> • MtBE (9,400 µg/m3) <br /> • TPHg (26,000 µg/m3) <br /> No constituent was detected above the ESL thresholds during the additional soil gas survey. <br /> Results are summarized below: <br /> • Benzene was non-detect above reporting limits (80 ' g/m3) in all soil gas sarnples. <br /> • Toluene was detected in all the soil gas samples. The concentrations ranged from 130 <br /> (SG-7 @ 7 purge volumes and SG-8) and 190 µg/m3 (SG-7 @ 1 purge volume). <br /> These levels are more than 2 orders of magnitude below the-ESLs. <br /> • Ethyl benzene was non-detect above reporting limits (100 11g/m) in all soil gas <br /> samples. <br /> • m,p-Xylenes-were detected in all the soil gas samples. The concentrations ranged <br /> from 130 (SG-8) and 200 µg/m3 (SG-7 @ 3 purge volumes). These levels are <br /> approximately 3 orders of magnitude below the ESLs. <br /> • o-Xylenes was non-detect above reporting limits (100 µg/m3) in all soil gas samples. <br /> • MtBE was non-detect above reporting limits {100 µg/m3) in all soil gas samples. <br /> a <br />