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Updated Site Conceptual Model and First Quarter 2002 Monitoring and Remediation Report Cleanup and Abatement Order No 5-00-707 EAI Project No 1232 • Combination of vapor extraction and air sparging employing all air sparging wells The system was running for approximately three hours • Air sparging only (i e , no vapor extraction) All wells except MW-23S were disconnected from the air sparging system Well MW-23S is screened 85 to 90 feet bgs while other sparging wells are screened from approximately 55 to 60 feet bgs, and therefore, well MW-23S requires higher air pressure than other wells During sparging of all wells except well MW-23S, the pressure at the compressor discharge was approximately 20 psig During sparging of well MW-23S, the compressor discharge pressure raised to 50 psig A soil vapor sample from the inlet of the oxidizer was obtained Well MW-23S was sparged for approximately one hour before the system was switched to a combination vapor extraction and air-sparging mode 4.4 Remediation Results Since starting the remedial system, the thermal oxidizer has operated for a total of 5,260 hours and the sparging compressor for 6,011 hours, removing approximately 8,415 pounds of petroleum hydrocarbons from impacted soil and ground water (see Table 8) The amount of biodegraded hydrocarbons is not included in this total and is difficult to calculate Since restarting the reinediation system in June 2001, the thermal oxidizer has operated for 604 hours and the sparging compressor for 1,407 hours, removing only 55 pounds of petroleum hydrocarbons from the subsurface by vapor extraction (see Table 8) These results coupled with the rise in ground water beneath the sites, e g , over 23 feet in well MW-2 between March 1993 and March 2002 (see Table 6), indicate that the remaining contamination is confined to an area now in the saturated zone 4.5 Relocation of Remediation Compound ' Stone Brothers will be demolishingthe former Wards Auto Service Center and constructing a g new building on the site As part of these efforts, the remediation compound will be moved approximately 300 feet east of its current location Relocation of the remediation equipment and compound should be completed in April 2001 BHM 1232RO231 -8- ENVIRONMENTAL AUDIT, INC