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SB4 compared to SB I showed a 99 7% reduction of gasoline range hydrocarbons (TPHg), complete <br /> removal of benzene and toluene, and a 99 8% reduction of the xylenes <br /> SB7 compared to MW2 and MW3 respectively showed the following reductions TPHg at 96 9% <br /> and 99%, Benzene and Toluene complete removal, and Xylenes at 90 5%and 99% <br /> S136 compared to SB3 (highest noted contaminated area) and MW10 respectively, showed the <br /> following reductions TPHg at 99 2%and 96 6%, Benzene, Toluene and Xylenes complete removal <br /> GROUNDWATER <br /> Grab water samples obtained from soil borings SB5, S136 and SB7 on June 4 and 5, 1997 were <br /> compared to the historic water samples obtained from SB2 and SB3 on December 7, 1988, see Table <br /> and Charts <br /> Comparing SB3 to SB6 a 93% reduction in the amount of TPHg has been accomplished Benzene, <br /> Toluene and Ethylbenzene have been reduced to below laboratory lower detection limits and <br /> Xylenes have been reduced by 99% <br /> Similar reductions can be seen when comparing SB2 with SBS and SB7, or 92% and 85% for TPHg <br /> respectively While Benzene, Toluene and Ethylbenzene have been reduced to trace amounts <br /> Xylenes have been reduced to 54% and 13% respectively <br /> Confirmation soil boring SB7 was converted into a two inch PVC well that will be later used for <br /> vapor extraction and air sparging <br /> RECOMMENDATIONS <br /> I Manifold and connect newly installed well MW13 (SB7) into the vapor recovery system <br /> Connect MW2 and MW13 to an air sparging system When groundwater elevations are high <br /> (between 35 and 40 feet below top of casing) sparge both MW2 and MW13, when groundwater <br /> elevations are low (lower than 40 feet below top of casing) vapor extract from MW 13 Initially <br /> influence MW13 with vapor recovery, to remove accumulated petroleum hydrocarbon vapors <br /> and CO2, which should be present in this area <br /> 2 Within three months of sparging MW-2 and MW-13, sample all wells for dissolved oxygen, <br /> sulfate, nitrate, and ferrous iron to determine if natural attenuation is occurring at this site <br /> 3 Sample all wells for TPHg, BTEX and MTBE using 8020 method during the December 1997 <br /> quarterly sampling Confirm all MTBE responses with 8260 methou <br /> 4 Source removal has been accomplished and documented in the soils beneath this site with <br /> documentation borings SB4, S135, SB6 and SB7 The soil contamination for this site should <br /> be considered remediated with no further action needed <br /> 8 <br />