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I04 February 2004 AGE-NC Project No 95-0173 ' Page 9of10 • Utilizing a semi-logarithmic plot of ground water draw-down vs observation well distance to pumping well (Jacob straight-line method), a best-fit line was utilized to project a radius of influence for EW-1 at approximately 62 feet at 5 GPM (Appendix K, Figure 4) • Utilizing the Distance-Drawdown Method(Jacob straight-line method),a transmissivity was calculated at 565 ft'/day (equivalent to 4,216 gallons per day/ft) and a storativity value calculated at 0 11 (Appendix K, Table 4) I • Based on a transmissivity value of 565 ftZ/day and an aquifer thickness of 25 ft (screen interval at EW-1),a hydraulic conductivity value was calculated at 22 6 ft/day,or 0 008 cm/s (Appendix K, Table 4), a hydraulic conductivity of 0 008 cm/s is consistent with a screened interval located within a silty sand to fine sand (Appendix N) • Laboratory analysis of extracted water during the pumping test detected elevated concentrations of TPH-g and BTEX, the laboratory reported the sample chromatogram as having significant unmodified or weakly modified gasoline (Appendix L) 5.0. CONCLUSIONS Between 11 April 2000 and present(approximately 3%years), an in-situ air sparging system (IAS) system has been in continuous operation at the site to address petroleum-impacted ground water at depths between 25 and 38 feet bsg, subsequently identified as Hydrologic Unit I However, analytical results of ground water samples from on-site monitoring wells suggest that the 1AS system has been only moderately effective in reducing the overall mass of dissolved petroleum plume in Hydrologic Unit 1 Besides Hydrologic Unit 1,AGE subsequently identified another petroleunihydrocarbon-impacted interval (Hydrologic Unit 2, at between 38 and 65 feet bsg) in October 2001 on the basis of additional cone penetrometer data(Cone Penetrometer Testing Site Investigation -Fourth Quarter 2001,dated 19 February 2002)and water samples collected from wells AW-1 and AW-2,corrective action is now warranted in Hydrologic Unit 2 in the area between wells AW-1 and AW-2, but due to the slow pace and marginal effectiveness of IAS currently being encountered in Hydrologic Unit 1, and the unfavorable lithologic change between Hydrologic Unit 1 (less permeable silts and silty sand) and Hydrologic Unit 2(more permeable fine to medium sand),IAS will probably not be the optimal remediation alternative to address Hydrologic Unit 2 because of the high potential for air-flow channeling Based on the well-defined,laterally continuous, sandy nature of Hydrologic Unit 2, it would appear advantageous to implement a ground water extraction system screened through Hydrologic Unit 2, Advanced CeoEnviran mental,Inc I