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California R!onal Water Quality ontrol Board <br /> \� Central Valley Region ,l <br /> Steven T.Butler,Chair Gray Davis <br /> Winston H. Hickox <br /> Secretaryfor Sacramento Main Office Governor <br /> Environmental Intemet Address: http://N v v.sw cb.ca.gov/iwgcbi <br /> Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 <br /> Phone(916)255-3000•FAX(916)255-3015 <br /> 29 February 2000 <br /> UMr.N W.T. Nickerson <br /> UNOCAL Asset Management Group <br /> 2121 California Blvd., Suite 250 <br /> Walnut Creek, CA 94596 <br /> REVIEWOF1999QUARTERLYMONITORINGREPORTS, WESTERN FARM SERVICE <br /> (FORMER PUREGRO) STOCKTON, SAN JOAQUIN COUNTY <br /> I have received the quarterly monitoring reports (QMRs)prepared by Sierra-Pacific Group describing the <br /> groundwater quality relating to past activities at the former Puregro Stockton Facility. In this letter, I <br /> comment on the following reports: <br /> • 30 April 1999 First Quarter 1999 Quarterly Monitoring Report <br /> • 27 July 1999 Second Quarter 1999 Quarterly Monitoring Report <br /> • 29 October 1999 Third Quarter 1999 Quarterly, Semiannual and Annual Monitoring Report <br /> 17 January 2000 Fourth Quarter 1999 Quarterly Monitoring Report <br /> I also received the 20 January 2000 Feasibility Study Workplan, which I will review under separate <br /> cover. As we discussed in our 16 February telephone conversation, the feasibility study is one topic we <br /> will discuss during our meeting with you, Mr. Eric Chase of Sierra-Pacific, and Ms. Wendy Cohen and <br /> myself of the Regional Board staff, scheduled for 14 March at 10:00, at our office in Sacramento. As <br /> you know, the Site Cleanup Unit moved tol0365 Old Placerville Road, about three blocks from the main <br /> office. The mailing address remains 3443 Routier Road, and the phone numbers also remain the same. <br /> 1999 Summary <br /> The QMRs illustrate that there is a lot of valuable groundwater information available and the monitoring <br /> well locations maximize the quality of the data. <br /> The QMRs state that the primary influence on groundwater gradient and direction is the unlined <br /> Stockton Diverting Canal,which is 1,000 feet northeast of the Puregro facility. When flows in the canal <br /> are high, the gradient is perpendicular to the canal (southwest), and when flows are low, the gradient <br /> tends westward. The largest fluctuations in groundwater elevation in subsequent quarters are in the <br /> upgradient monitoring wells that are nearest the canal (MW-1, 3 and 10), and the lowest fluctuations are <br /> California Environmental Protection Agency <br /> 0*Recycled Paper <br />