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i <br /> fPage 4 <br /> iMs Margaret Lagono <br /> Quarterly Groundwater Monitoring Report - September 1996 (Third Quarter) <br /> October 28, 1996 <br /> Phase-separated hydrocarbons (PSH) were not observed in any of the monitoring wells <br /> Hydrocarbon-impacted groundwater was not detected in Monitoring Wells MW-2 through <br /> MW-8 except for a TVH-G concentration of 65 micrograms per liter (uglL) in Monitoirng <br /> Well MW-7 The groundwater hydrocarbon impact in Monitoring Wells MW-1 and <br /> MW-13 decreased from the previous monitoring event, but increased slightly in <br /> Monitoring Well MW-10 The greatest concentration of TVH-G(24,000 ug/L) and <br /> benzene (780 ug/L) occured in MW-1 Certified analytical results and the chain-of-custody <br /> I documentation are presented in Appendix C A summary of the laboratory analytical <br /> results, for the current monitoring event, is presented in Table 3, and graphical <br /> presentations for TVH-G and benzene are presented in Figures 4 and 5, respectively A <br /> summary of the historical analytical testing is presented in Table 4 As can be seen in the <br /> graph of Table 4, the benzene and TVH-G concentrations are generally trending <br /> downwards This decreasing concentration trend could be a combination of removal of <br /> the source, migration of the dissolved phase, and natural biodegradation processes <br /> RECOMMENDATIONS <br />' In addition to the typical groundwater testing activities scheduled for the next quarterly <br /> . monitoring period, Philip anticipates collecting data in order to assess natural <br /> biodegradation activities and estimate the duration of concentration attenuation Then a <br /> comparison of the estimated cost of quarterly monitoring for this duration versus <br /> estimated remediation costs can be performed <br /> L <br /> C OSING <br />' The next quarterly groundwater monitoring for this facility is scheduled for mid-December <br /> 1996 Results from that event will be duly submitted to San Joaquin County Public Health <br /> Services If you have questions, or desire additional information, please cal! Mark <br />' Milward or Ken Olson (Philip) at (618) 281-7173 <br /> Sincerely, <br /> PHILIP ENVIRONMENTAL SERVICES CORPORATION <br /> �enn. son, E I T <br /> I 1 ist/Geolo ical Engineer BRED G0 <br /> Hydrogen og g <br />' R. JOHR v' <br /> John Carrow, R G No 5525 N —3 <br /> * CARROW <br /> Geo gist No 5525 <br /> x <br /> 1 <br /> 1 <br />