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RM Assooates 701-0102 ' concentrations in groundwater samples from BEI-MW3 originally detected as high as 100,000 gg/L and 11,000 gg/L, have been reduced to 430 gg/L and 9 3 gg/L, respectively 32 Microbial Activity Operation and maintenance inspections during the remediation period observed an inordinate amount of bio-mass evident in the groundwater immediately after its extraction This was particularly ' evident during the initial months after remediation startup, requiring weekly back flushing of the GAC canisters to remove the accumulated bio-mass This occurrence provided evidence that the physical and chemical characteristics for bio-degradation in the groundwater, both above and below the surface, were particularly favorable RMA believes the migration of fresh oxygenated air and water through the site, as a result of the soil vapor and groundwater extraction, may have caused the destruction of greater amounts of hydrocarbons, by the process of enhanced bio-degradation, than ' have been recovered above ground in the respective SVE and groundwater carbon treatment units In the last months of system operation,before it was shut down In February 2000,the amount of bio- mass produced had declined to negligible, the result of diminished concentrations of hydrocarbon remaining in the groundwater The significance of known favorable bio-degradation activity extends beyond the period of active remediation Given the relatively minor concentrations of petroleum hydrocarbons remaining at the site, it is extremely likley that the remaining concentrations will degrade to near non-detectable levels within a relatively short period of a few years, if that long 3.3 SVE Radius of Influence Testing During the December 10, 1998 monitoring event, a soil vapor extraction radius of influence test was conducted to determine the vacuum influence surrounding the co-extraction well EW-1 As soil vapor was extracted from EW-1, the vacuum influence away from the well was measured at three surrounding monitoring wells While pumping 100 cubic feet per minute from EW-1, the vacuum in the extraction well is only about 3 inches of mercury (39 inches of water) This attests to the relatively high degree of gas permeability in t e soi surroun Ing the well Using supersensitive ' magnahelix vacuum gauges,the most notable vacuum effect was observed in monitoring well BEI- MW1, located approximately 40 feet from the co-extraction well A differential of 0 3 inches of water was observed between the Vacuum measured in the well and ambient air pressure The ' vacuum differential for BEI-MW3, located only about 10-12 feet from the extraction well was only 0 12 inches of water The vacuum influence between co-extraction well EW-I and monitoring well BEI-MW2, located approximately 40 feet apart, was evident but even smaller, having a differential ' of 0 01 inches of water In summary, the results show the SVE process to have been very effective The probable greatest impact of SVE, however, may have been through the enhancement of biological activity as oxygen rich air was drawn through the soil 34 Summary of Product Removal The duration of active remediation extended from mid-February 1998 to mid-February 2000 During this period, an estimated amount of approximately 620 ounds of TP were recovered from an estimated 84 2 million cubic feet of extracted soil vapor(see Table 6) Additionally, approximately Page 6 of I I