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Weekly bio-venting of MW-8 and MW-12 are being conducted by Lawrence Tank Testing Currently the groundwater is too high, no slotted casing is exposed above groundwater at MW I2 to conduct bio-venting As of September 23, 1997 the 2 hour Once a week bio venting of MW-8 has removed a calculated 4 99 pounds of gasoline range Hydrocarbons and a total of 420 3 pounds of hydrocarbons as gasoline and CO2 The average flow rate is 50 8 efm, with a vapor stream consisting of TPHg of 0 001 mg/L and CO2 at 1 5%, see Table 3 and Appendix D Summary SOIL Confirmation soil sample borings S134, S135, S136 and SB7 were drilled and sampled (June 1997) near previous sample boring S131, SB2 and S133 (December 1988), see Figure 3 Charts were developed to show the reduction comparisons of the soil sample results, see previous report CONFIRMATION OF THE EFFECTS OF THE VAPOR EXTRACTION SYSTEM, dated July 31, 1997, Table 2 for results No MTBE was noted in any of the soil samples Comparing the historic highest contaminated depth, fifty feet below ground surface (bgs), the following reductions in contaminants are noted and are representative of the overall site conditions SB4 compared to SBI showed a 99 7% reduction of gasoline range hydrocarbons (TPHg), complete removal of benzene and toluene, and a 99 8% reduction of the xylenes SB7 compared to MW2 and MW3 respectively showed the following reductions TPHg at 96 9% and 99%, Benzene and Toluene complete removal, and Xylenes at 90 5% and 99% SB6 compared to SB3 (highest noted contaminated area) and MW10 respectively, showed the following reductions TPHg at 99 2% and 96 6%, Benzene, Toluene and Xylenes complete removal It is felt through vapor extraction and limited over-excavation of the UST area that the source (soil contamination) at this site has been removed and that soils portion of the remedial action efforts has peen accompiished and that no further at tions are necessary GROUNDWATER Grab water samples obtained from soil borings SB5, SB6 and S137 on June 4 and 5, 1997 were compared to the historic water samples obtained from S132 and SB3 on December 7, 1988, see Table and Charts in CONFIRMATION OF THE EFFECTS OF THE VAPOR EXTRACTION SYSTEM, dated July 31, 1997 Comparing S133 to SB6 a 93% reduction in the amount of TPHg has been accomplished Benzene, Toluene and Ethylbenzene have been reduced to below laboratory lower detection limits and Xylenes have been reduced by 99% 4