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1 ' 3. CURRENT ACTIVITIES AND DATA GAP INVESTIGATIONS A review of the historical data at the site in comparison to generally accepted data needs to perform a nsk-based corrective action (RBCA) analysis identified two data gaps (1) soil gas data, and (2) a well survey These two tasks, summarized below, were performed prior to conducting the RBCA analysis 3.1 SOIL AND SOIL GAS INVESTIGATION In order to collect soil vapor samples at the site soil borings S B1 through SB8 were installed on P P � g 28 December 2000 by Vironex of Hayward, California (C57 License #705327), using a single tube direct-push method The locations of these soil borings, as presented on Figure 2, were selected to include the former pump islands and former tank field, as well as the onsite locations directly above the highest detected concentrations of petroleum hydrocarbons in soil and groundwater Drilling and sampling protocols are summarized in Appendix E Soil samples were collected from sleeves inside a 1 5-inch-diameter sample barrel attached to the end of the direct-push rods One soil sample was collected from each boring at 1 5-2 feet bgs and submitted to Southern Petroleum Laboratories in Houston, Texas, for analysis The samples were analyzed for Total Organic Carbon (TOC) by SW9060, moisture content by D2216, and porosity by ASTM D2974 The locations of the soil borings are shown on Figure 2 The analytical results for the soil samples are presented in Table 3 The soil sample laboratory • analytical reports are included in Appendix F Soil gas samples were collected in 6-liter Summa canisters from the borings at 2 5-3 feet bgs and 5 5-6 feet bgs using the GeoProbe Post-Run Tubing (PRT) System The soil vapor samples were analyzed for TPH-g, BTEX, oxygenates, and additives by EPA Method TO-14 The vapor samples were analyzed by Air Toxics Ltd of Folsom, California Benzene was detected at concentrations ranging from 1 5 parts per billion volumetnc (ppbv) in SB7 (2 5-3') to 5 8 ppbv in SB8 (5 5-6') MTBE was detected at concentrations ranging from 3 7 ppbv in SB7 (2 5-3') to 48 ppbv in SB8 (5 5-6') TPH-g was detected at concentrations ranging from 120 ppbv in S135 ' (5 5-6') to 1,800 ppbv in SB8 (5 5-6') Ethanol was detected at a maximum concentration of 54 ppbv in SB8 (5 5-6') Methanol was detected at a maximum concentration of 400 ppbv in samples collected from SB8 (2 5-3' and 5 5-6') The oxygenates TBA (tert-butyl alcohol), IPE (isopropyl ether), ETBE (ethyl t-butyl ether), and TAME (t-amyl methyl ether) and the additives 1,2-DCA (1,2-dichloroethane) and EDB (ethylene dibromide) were not detected in any of the soil vapor samples The analytical results for the soil vapor samples are presented in Table 4 The soil vapor laboratory analytical reports are included in Appendix G 32 WELL SEARCH In further support of the RBCA analysis, a well survey was performed to identify wells within a one-mile radius of the site The results of the well search are summarized below, and graphically presented in Figure 9 G Tio}ects1739421NIASTERNIVP\RnOHOI\tetG doc 5