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18 rune 2001 AGE-NC Project No. 98-0432 Page 5 of 6 ' 4.0. SUMMARY AND CONCLUSIONS The ground water table occurred within the screened interval of the wells and the most likely's6urce ' of the extracted ground water was from the highly permeable sand, encountered from 20 feet to 30 feet bsg. The implications from the May 2001 aquifer ground water pumping tests are: • During the constant-rate pumping test of 23 May 2001, ground water draw-down of at least ' 5 feet was observed in extraction well EW-1 following 12 hours of continuous pumping operation; ground water draw-down was observed.in well MW-1 (5 feet away) at 0.7 feet ranging to 0.13 feet in well MW-2 (85 feet toward the west). ' Utilizing the Distance-Drawdown Method(Jacob straight-line method), a transmissivity was calculated at 700 ft2/day(5,223 gallons per'day/ft) and a storativity of 0.047. ' Based on transmissivity value of 700 ftt/day and the aquifer thickness equal to at least 15 feet (screen interval at EW-1), a hydraulic conductivity value was calculated at 348 ft/day, or 0.123 cm/s; a hydraulic conductivity of 0.1 cm/s is consistent with a screened interval located w within a clean sand or gravel (Appendix F). • Utilizing field data, a radius of influence was approximately 95 feet at 5 gpm. 1 Low concentrations of BTEX were rem'oved'duri.ng the extraction test, generally decreasing with time. MTBE concentrations detected in the grab ground water samples were six-percent ' of the maximum MTBE concentration detected in the samples collected from well MW-l. • MTBE-impacted ground water recovery appears to have the potential to remove or reduce the MTBE concentrations in the ground water at the site. • ' 5.0. RECOMMENDATIONS Based on the ground water aquifer pumping test results, AGE believes that a ground water recovery ' system can be developed to provide hydraulic control of the plume of dissolved MTBE and reduce the mass of MTBE. 1 Advanced GeoEnvironmental,Inc.