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California Regional Water Quality Control Board <br /> Central Valley Region ,:/ <br /> on H.Hickox Sacramento Main Office Gray Davis <br /> Winston <br /> H. for Internet Address: http://www.swreb.ca.gov/—rwgcb5 Governor <br /> Environmental 3443 Routier Road,Suite A,Sacramento,California 95827-3003 <br /> Phone(916)255-3000•FAX(916)255-3015 <br /> Protection <br /> 12 December 2000 <br /> 0 <br /> 0 <br /> Mr. W. T. Nickerson <br /> UNOCAL Asset Management Group <br /> 8788 Elk Grove Blvd, Bldg 3, Suite 15 <br /> Elk Grove, CA 95624 <br /> DRAFT REVISED MONITORING AND REPORTING PROGRAM, REVIEW OF <br /> GROUNDWATER MONITORING REPORTS, WESTERN FARM SERVICES (FORMER <br /> BREAIPUREGRO), STOCKTON, SAN JOAQUIN COUNTY <br /> In a 28 July 2000 letter, your consultant,Mr. Eric Chase of Sierra-Pacific Group,proposed revisions to <br /> Monitoring and Reporting Program No. 96-816 (MRP) which applies to UNOCAL Corporation's former <br /> Brea/PureGro facility in Stockton, which is currently operated by the Western Farm Services, Inc. We <br /> have reviewed this request and a draft revised MRP is enclosed for your review and comment. We have <br /> also reviewed the following groundwater monitoring reports pertaining to the Stockton facility prepared <br /> for UNOCAL by Sierra-Pacific Group: <br /> • 30 April 2000 First Quarter 2000 Quarterly Monitoring Report <br /> • 18 July 2000 Second Quarter 2000 Quarterly Monitoring Report <br /> • 31 October 2000 Third Quarter 2000 and Annual Monitoring Report <br /> The First and Third Quarterly Monitoring Reports (QMRs) describe semi-annual constituent monitoring <br /> results whereas the Second QMR describes groundwater elevation monitoring, pursuant to the MRP. <br /> GROUNDWATER MONITORING REPORTS <br /> Thank you for incorporating the graphical and tabular changes to the QMRs as I requested in my <br /> 29 February 2000 letter. <br /> During the first quarter of 2000, the terminal well, MW-12, contained the volatile organic compounds <br /> 1,2-dichloropropane (1,2-DCP), dibromochloromethane (DBCM), chloroform and methylene chloride <br /> for the first time since the well was installed in November 1998. This is a significant finding that <br /> Sierra-Pacific should have listed in.the Executive Siimmary of the first quarter report. MW-12 contained <br /> only chloroform in the September 2000 monitoring event, but given the seasonal fluctuation in <br /> consituent concentrations observed in other wells at this site, the spring finding suggests that the plume <br /> terminus is arriving at MW-12. <br /> California Environmental Protection Agency <br /> ea Recycled Paper <br />