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12 August 1996 r <br /> AGE-NC Project No 95-0142 <br /> IPage 3 of 4 <br /> 33 ANALYTICAL RESULTS OF PURGED WATER SAMPLES <br /> TPH-g was not detected in samples collected from either drum at the site Benzene, toluene and <br /> xylenes were detected in the drum samples at concentrations up to 1 5 ppb The laboratory report <br /> (MAI Laboratory I D Nos 65623 and 65627) and chain-of-custody are included in Appendix B <br /> I <br /> 4.0. CONCLUSIONS AND RECOMMENDATIONS <br /> 41 CONCLUSIONS <br /> Similar to the March 1996 monitoring event, the greatest concentrations of dissolved petroleum <br />' hydrocarbons are detected in the sample collected from VE-1, which is located in the vicinity of the <br /> former TK1-90 excavation <br /> Based upon the most recent ground water data, the ground water surface is above the top of the <br /> screened casings of MW-1, MW-2 and MW-3, therefore, samples collected from these wells may <br /> not be representative of the actual aquifer conditions <br /> 42 RECOMMENDATIONS <br /> We do not recommend the installation of additional ground water monitoring wells at this time <br />' However, additional wells may be required, if ground water surface elevation remains above the top <br /> of the screened intervals in monztonng wells Additional wells may also be required if the dissolved <br />' hydrocarbon plume migrates south of MW-2 or northeast of MW-4 <br /> The next quarterly ground water monitoring should be scheduled for September 1996, if ground <br /> water elevations are below the top of the screened intervals, wells MW-1 through MW-4 should be <br /> sampled Additionally, a ground water sample should be collected from vapor well VW-1 to <br /> determine the dissolved hydrocarbon concentration in the vicinity of the former UST area <br /> Petroleum hydrocarbons were detected at low concentrations in the purged water samples However, <br /> the concentrations should not exceed acceptable limits for discharge into the City of Stockton <br />' treatment plant Therefore, we recommend obtaining permission from the City of Stockton to <br /> dispose of the purged water into the sanitary sewer <br /> , <br />