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A grab groundwater sample collected from Boring E3-2 (E3-2GW) showed only one detection <br /> (2.5 ug/L of acenaphthene). All other results from the grab groundwater sample were non- <br /> detect. <br /> Delineation of Impacts <br /> Based on review of the data generated during the RI/SSI, multiple areas of impact(AOI) for soil, <br /> soil gas and groundwater were identified at the Site and are presented in Figure 14. Further <br /> definition and brief descriptions of constituent impacts associated with the AOIs are provided <br /> below. <br /> Soil AOIs <br /> Impacts in soil at the site attributable to former MGP operations and/or a release from the <br /> gasoline UST were observed in multiple AOIs. Soil with elevated B(a)P equivalent <br /> concentrations were observed in AOI 1 to a maximum depth of approximately three feet bgs; in <br /> AOI 2 to a depth of approximately two feet bgs; in AOI 3 to a maximum depth of 2 feet bgs; in <br /> AOI 4 to a depth of approximately 1.5 feet bgs; and in AOI 6 to an approximate depth of 3 feet <br /> bgs. <br /> In addition to the PAH impacts identified above, elevated TPH impacts (>1,000 mg/kg) in AOI 3 <br /> were observed at a depth of between 10 and 15 feet bgs. Additionally, AOI 4, where the former <br /> gasoline UST was located, exhibited elevated TPH-g concentrations (>100 mg/kg) at <br /> approximately 10 feet bgs. Shallower samples in AOI 4 showed higher levels of TPH-mo <br /> (>1,000 mg/kg) that were limited to 1 foot bgs. AOI 6 had TPH concentrations greater than <br /> 1,000 mg/kg at a depth of one foot bgs that appears to extend to three feet bgs based on <br /> visual/olfactory/PID observations. <br /> VOC constituents in soil were only observed in the samples collected in AOI 4. These <br /> constituents had relatively low concentrations and are attributable to the former MGP operations <br /> and/or the gasoline UST that has been removed from this location. Title 22 Metals <br /> concentrations in soil encountered during the RI/SSI are similar to background; therefore, no <br /> AOIs are included with metals impacts. <br /> Soil Gas AOIs <br /> Soil gas impacts have been identified in two AOIs at the Site (AOI 4 and AOI 5). AOI 4 is <br /> located in the northwest corner of the Site (Grid A3 of Figure 14) near the current PG&E <br /> warehouse and is associated with soil gas point A3-SG1. This area is impacted with VOCs in <br /> soil gas related to the gasoline UST that has been removed. Detected constituents in AOI 4 are <br /> those typically associated with USTs containing gasoline and include: BTEX, 1,2,4- <br /> trimethylbenzene, 1,3,5-trimethylbenzene, 2,2,4-trimethylpentane, 4-ethyltoluene, cumene, <br /> cyclohexane, heptane, hexane, and propylbenzene. Impacts in this AOI were delineated through <br /> installation and sampling of five additional soil gas points (A3-SG2 through A3-SG6). Results <br /> from these additional soil gas points showed concentrations several orders of magnitude below <br /> the results from A3-SG1 and below residential CHHSLs in shallow soil gas; therefore, <br /> delineation has been achieved at this location. <br /> The second AOI with soil gas impacts is AOI 5, located in the northeastern portion of the Site <br /> (Grid Al in Figure 14). This AOI is characterized by PCE impacts in soil gas point Al-SG1 <br /> where PCE was detected at 1,500 ug/m3. Due to impacts in this AOI, identified during the RI, <br /> PARSONS 5 FINAL RI REPORT-FORMER TRACY MGP <br /> APRIL 2010 <br />