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'`� <br /> t QIeYiOn <br /> Chum, U.S.A. Inc. <br /> { 2410 Camino Ramon,Son Ramon,California•Phone 14151642-9500 <br /> Mail A4Qrosx P.1.Sax 5004,San Ramon,CA 94507 0904 <br /> Marketing Department <br /> March 18, 1991 <br /> Mr.Harlin Knall <br /> San Joaquin County Environmental Health RgCEIVCU <br /> P.O.Box 2009 MAR 2 <br /> Stockton,CA 95201 E/V 1 19g, <br /> Re: Former Chevron S.S.147 S.'EI Dorado Street Stockton,CA MST SERV,�cA ES <br /> LTf; <br /> Dear Mr Knoll: <br /> Enclosed is a quarterly monitoring report dated February 22, 1991 which describes groundwater 3 <br /> sampling by Chevron's consultant,Groundwater Technology(GTI), on January 9, 1991 at the <br /> d site referenced above. <br /> Groundwater gradient,as calculated from water levels measured January 9, 1991,was different <br /> than that calculated from the previous measurement on August 20, 1990 by approximately ninety <br /> degrees. The northeast gradient from the more recent measurement is consistent with the expected <br /> gradient,while the previous northwest gradient may be an anomaly. <br /> Due to the contradiction in the gradient information,Chevron proposes monitoring the gradient and <br /> obtaining groundwater samples quarterly for one full year cycle before deciding on the placement <br /> of groundwater wells or BAT probes to further define the extent of dissolved phase hydrocarbons <br /> in the groundwater. <br /> By January 1992, the gradient should be well defined and the applicability of the BAT probe <br /> sampli.,,;system should be well documented. <br /> If you have any questions or comments,please contact Mr.Clint Rogers at(415)842-8558. <br /> .. Sincerely, F <br /> Chevron U.S.A. <br /> f <br /> BY <br /> Clint B.Rogers r <br /> ` Environmental Engi ser <br /> Enclosure <br /> cc--41m]Maughan,Central Valley RWQCB,-Sacramento,CA-- - —-. ---- —= --- --- <br /> Ramon Guerrero, 13.27 S.Wilson Way,Stockton,CA 95275 <br /> r <br /> Sandra Lindsey,GTI,Concord,CA <br /> ., ... - <br />