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Firestone Service Center 400 North El Dorado, Stockton, California February 2, 1994 Soil Rernediation Plan—2072.01 Page 5 of 6 • 34 Permitting Permits required to operate the system will be obtained prior to installation. Applicable permits will be obtained from the following agencies • San Joaquin County Public Health Services • San Joaquin County Air Pollution Control District • City of Stockton Public Works Department 3.5 Site Closure Criteria Since the soil sample analytical results from the October 1993 site assessment indicate non-detectable quantities of NPH, RMI proposes to determine site closure based upon analysis of system vapor discharge and monitoring point(s) vapor concentrations The regulations establish a compliance level for soil based upon a site rating system The maximum allowable hydrocarbon level for soil remaining in place at this site, as determined by The Leaching Potential Analysis, Table 2-1 in the CA-LUFT Manual, is 100-ppm TPH-gas, or TVPH Since the regulations do not identify an action level for soil gas, it is suggested that a target level for soil gas concentration be set at 100-ppm TVPH as determined by EPA Method TO-14. Once the target soil gas concentration is achieved, the active well will be turned off to allow for recharge of vapors. After a minimum of a 1 week system off-time, vapors will be extracted from the idle well to determine if recharge has occurred. If soil gas concentrations remain below the 100-ppm target level, soil gas samples from any impacted monitoring points with corresponding depths will be analyzed to verify concentrations are below the target level Each well system will be handled similarly, although operation time may differ System operations will proceed as follows Initially, vapors will be extracted from well VE 2 until soil gas concentrations reach the target level At this point, well VE 2 will be disconnected and vapors will be extracted from well VE 1 . Once target levels have been achieved in VE 1 , the VES unit will be reconnected to extract vapors from VE 2 Extracted vapors from VE 2 will be sampled immediately after restart If vapor concentrations have not increased above the target level after pulsing the well, as described herein, extraction at this well will be terminated Well VE 1 will then be reconnected following similar procedures. Once it has been shown that soil gas vapors are not recharging during system shut-off times, site closure will be requested RYAN -NMMPSY, HTCORPORATED Denvw Fnvhv=w W Construction Nk nmement IAs Angdo