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..—_ _ .. ..a... .r.•.v....�,...,.. i•... .. ....r ..r .-.. .:...,a....r..a. .a:Y. ...-..... ..._....ti.ur•r. �.-.K n.rv.-..._.....�•.}.s. .. .. ...r. ..—..w v�.aw.��....--1 <br /> Mr. Nathan Esformes '"'� Iwo <br /> -2- <br /> Disposal to the wastewater treatment system is unacceptable since this system has not been in <br /> compliance with the waste discharge requirements (WDRs) Order No. 92-142. Assuming the <br /> wastewater treatment system is brought back into compliancy with the WDRs, any additional discharges <br /> to the system must not exceed the design capacity of the system. <br /> Evaluation of the Bioremediation <br /> I do not agree that the analytical results show that the bioremediation has reduced chloroform <br /> concentrations in MW4A. Although concentrations in MW4A have decreased, the increased <br /> concentrations of chloroform in downgradient monitoring wells MW2, MW6, and MW7 suggest the <br /> decreased concentrations in MW4A are a result of the plume migrating away from the source area. <br /> Gas Phase Migration <br /> I do not agree, as I stated in my 18 April 1995 letter, that the 43 µg/1 chloroform detected in MW7 in <br /> December 1994 was due to gas phase migration resulting from unprecedented heavy rains. As I stated <br /> in my previous letter, the increase in chloroform occurred before the heavy rains in January and March <br /> 1995. If anything, the heavy rains resulted in a decrease in chloroform concentrations in MW7, i.e., <br /> from 43 µg/1 in December 1994 to 22µg/1 in March 1995. <br /> I also do not agree that gas phase migration of chloroform has caused the recent increases of chloroform <br /> in MW 1. These increases may be due to ground water mounding caused by disposal of the extracted <br /> ground water into the former rinse water pond and the resulting radial movement of ground water away <br /> from the pond towards the area of MW L <br /> By 12 July 1995, please submit an addendum to the work plan which addresses the comments above. <br /> The addendum should propose additional monitoring well(s) to determine the extent of chloroform <br /> contamination, propose a remediation alternative which will contain all known ground water <br /> contamination, and propose an acceptable method of treatment and/or disposal of any extracted ground <br /> water. <br /> If you have any questions you may call me a< (916) 255-3048. <br /> POLL1Yo WR <br /> Associate Engineering Geologist <br /> PAL:ms <br /> cc: San Joaquin County Public Health Services, Stockton <br /> Mr. Robert Dixon, AGRO Environmental Services, Stockton <br /> Mr. Michael Campos, Graham & James, Sacramento <br /> Mr. John Kramer, Condor Earth Technologies, Stockton <br />