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Momtonng Well Installation Report - Former Chevron Service Station A9-5775 June 2 1999 fraction organic carbon The composite sample from the drill cuttings was analyzed for TPHg, BTEX and total lead Copies of the laboratory analytical reports and chain -of -custody records are Included in Appendix G 5.0 RESULTS 5.1 Subsurface Conditions Soil encountered in borings SB -1 and MW -1 through MW -4 consisted predominantly of interbedded silts, clays and sands to the total depth explored of 72 5 feet bgs Backfill material was encountered immediately beneath the ground surface in borings SB -1 and MW4 and extended to the approximate depths of 22 and 8 5 feet bgs respectively Groundwater was encountered and stabilized at depths between 53 and 55 feet bgs Detailed descriptions of the subsurface materials encountered during drilling are presented on the boring logs in Appendix C The site lithology also is depicted on Cross Sections A -A' and B -B' (Figure 5) The cross section lines are shown on Figure 2 Based on the groundwater monitoring data collected on February 3, 1999, shallow groundwater beneath the site appears to flow to the southeast at an approximate gradient of 0 007 (Figure 4) 5.2 Soil Analytical Results • Gasoline and unidentified hydrocarbons in the C6 -C12 range reported by the laboratory as TPHg were detected in the soil samples collected from boring SB -1 at 30 feet bgs (160 ppm) and 33 feet bgs (1,200 ppm) I ow TPHg concentrations (not exceeding 3 ppm) were also detected in the soil samples collected from boring SB -1 at depths of 37 and 43 feet bgs (unsaturated samples) and at depths of 58 and 65 feet bgs (saturated samples) TPHg were not detected in the soil samples collected from borings MW -1 through MW -4 with the exception of the sample collected from boring MW -3 at 21 feet bgs which contained 2 ppm TPHg Benzene (up to 0 81 ppm) was detected in the soil samples collected from boring SB -1 Fourteen of the forty-one analyzed soil samples from borings MW -1 through MW -4 contained benzene at low concentrations (up to 0 058 ppm) MtBE was detected in the samples collected from boring SB -1 at concentrations ranging from 0 30 ppm to 110 ppm The samples collected from boring SB -1 at 30, 37 and 40 feet bgs contained EtBE (up to 1 3 ppm) The sample collected from boring SB -1 at 30 feet bgs also contained tAME (0 34 ppm) Other oxygenate compounds were not detected in the soil samples collected from boring SB -1 Twenty of the forty-one analyzed soil samples from borings MW -1 through MW -4 contained MtBE at concentrations up to 0 64 ppm Ethanol, t -Butanol, DIPS, ELBE or tAME were not detected in the samples collected from borings MW -1 through MW -4 Laboratory analytical results for the samples collected from borings SB -1 and MW -4 indicated fraction organic carbon ranging from <0 020% to 0 032%, dry density ranging from 1 62 gram per cubic 346408042 5