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Similar reductions can be seen when comparing SB2 with S135 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% of their original values respectively <br /> Confirmation soil boring S137 was converted into a two inch PVC well MW13 This well along with <br /> MW1, MW2, MW3 and MW10 is currently being used for vapor extraction <br /> MW2 and MW13 will also be connected for air spargrng in the near future to introduce and make <br /> available oxygen for biodegradation of the down gradient wells MW8 and MW 12 <br /> The gasoline range hydrocarbon plume associated with this site is declining in concentration and <br /> should continue to do so with the removal of the source to the soils beneath this site With continued <br /> vapor recovery, the bio-venting of MW8 and MWI2 and the commencement of spargrng at MW2 <br /> and MW13, the reductions in groundwater concentrations should continue to decline at MW8 and <br /> effects should be seen at MW 12 during the January-March, 1998 Quarterly sampling <br /> RECOMMENDATIONS <br /> I Connect MW2 and MW13 to an air spargzng 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 MW13 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 spargrng 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 method <br /> 4 Source removal has been accomplished and documented in the soils beneath this site with <br /> documentation borings SB4, SB5, SB6 and SB7 The soil contamination for this site should <br /> be considered remedrated with no further action needed <br /> 5 <br />