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' 15 October 2002 • AGE-NC Project No 96-0232 ' Page 13 of 19 ' Aquifer Zone (130-150 feet bsg) The Rocky's Upper Zone was the shallowest groundwater zone screened in the destroyed Rocky's domestic drinking water well ' The results of pump and treat ground water remediation between 27 March and 13 June 2002 are as follows ' • Approximately 1,485,238 gallons of MTBE-impacted ground water were extracted from wells EW-4, EW-5, EW-9 and EW-10, which were completed in the First Zone aquifer (Appendix A, Table 8) Due to a pump malfunction, well EW-8 was substituted for EW-9 ' between 08 August and 25 September 2002 • A total volume of approximately 15,458,051 gallons of MTBE-impacted water has been ' treated at the site since the start-up period in November 2000 (Table 8) • Dissolved MTBE was detected from grab samples collected at the influent-end of the treatment system at concentrations between 9 1 µg11 and 17 µg/l (Table 1) 1 • Laboratory analysis of three grab water samples collected at the effluent-end of the pump and treat system did not detect any petroleum constituents of concern (Table 1) o Between 13 June 2002 and 29 July 2002, the mass of MTBE-impacted ground water processed during operation of the pump and treat system was calculated to be 5,748,253 pounds Multiplying the average MTBE concentration (18 gg/l) by the pounds of MTBE- extracted water yielded a mass of approximately 0 10 pounds of MTBE removed from the extracted ground water(Table 8, Appendix D) • Between 29 July 2002 and 27 August 2002, the mass of MTBE-impacted ground water processed during operation of the pump and treat system was calculated to be 5,018,774 pounds Multiplying the average MTBE concentration(13 4 ggh)by the pounds of MTBE- extracted water yielded a mass of approximately 0 07 pounds of MTBE removed from extracted ground water (Table 8, Appendix D) 1 • Between 27 August and 05 September 2002, the mass of MTBE-impacted ground water processed during operation of the pump and treat system was calculated to be 1,615,402 pounds Multiplying the average MTBE concentration (9 4 µg11) by the pounds of MTBE- extracted water yielded a mass of approximately 0 02 pounds of MTBE removed from extracted ground water (Table 8, Appendix D) • On 25 September 2002, the ground water pump-and-treat system was suspended due to a detection of hexavalent chromium in the effluent grab water sample at a concentration of 0 30 gg/l The pump-and-treat system effluent was resampled on 25 September 2002, and ' the laboratory reported non-detectable levels of hexavalent chromium (less than 0 5 µg/l) • Advanced GeoEnvironmental,Inc