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1 ' Second Quarter 1996 Groundwater Monitoring&Remediation Status Report Moore Petroleum, 14800 W Frontage Rd,Manteca,CA August 7, 1996 Page 4 ' During this reporting period,water flow through the treatment system has ranged from 1 0 gallon g per minute (g p m) on May 16 to 4 0 g p m on May 3, 1996 Groundwater samples were ' collected from the system influent and effluent on April 5, May 3, June 13 and July 19, 1996 to demonstrate compliance with Land Discharge Permit Order No 91-25013 ' On all four sampling events, sample analytical results indicated below laboratory detection limits for concentrations of both TPI, as gasoline, and BTEX with the exception of the carbon inlet sample collected on July 19, 1996 which contained toluene at 0 35 ug/l, which is slightly above the ' detection limit of 0 30 ug/l As a result, system extraction rates for both TPq as gasoline, and benzene for this reporting period were zero Laboratory analytical results and chain-of-custody ' forms are contained in Appendix B As of July 19, 1996,the groundwater treatment system has extracted approximately 18 lbs of ' TPH, as gasoline, and 0 37 Is of benzene System operating data are contained in Table 5 Mass extraction rates to date,based on laboratory analytical results, are contained in Table 6 RECOMMENDATIONS ' The groundwater extraction system is currently extracting groundwater from monitoring wells MW-1 through MW-4 Groundwater samples collected from these four wells have been below ' laboratory detection limits for total petroleum hydrocarbon(TPH), as gasoline, TPK as diesel, and benzene, toluene, ethylbenzene and xylenes(BTEX)for four consecutive quarters with the exception of the sample collected from MW-3 on February 15, 1996 which had TPK as gasoline, ' detected at 65 ug/l,which is slightly above the detection limit of 50 ug/l Groundwater samples collected from these four monitoring wells have consistently been testing positive for 1,2 ' Dnchloroethane(EDC) at levels slightly above detection limits The highest concentration detected in these four wells in the May 16, 1996 quarterly groundwater sampling was in MW-2 at 2 O'ug/I A review of the lustoncal EDC analytical results indicate no reduction trend in the EDC ' concentrations as a result of the operation of the groundwater extraction system The existing remediation system was designed to remove petroleum hydrocarbons, not EDC A review of these facts leads Apex to the conclusion that the groundwater extraction system has served its purpose by ' reducing the TPI, as gasoline, TPI, as diesel, and BTEX concentrations to below laboratory detection hints but is not effective in reducing the groundwater EDC concentrations and is no longer a cost effective remedial technology at the subject site Apex recommends shutting down l the groundwater extraction system during the next quarterly sampling event which is scheduled for ie August 22, 1996 1 1