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_ a <br /> Q11'i mn <br /> Chevron U.S.A. Inc. <br /> 2410 Camino Raman,San Ramon,California•Phone 14151842-9500 <br /> W4 Mdresr IT sox WA San Ramon,to 94593 0804 <br /> MarketingDepanment March 1$, 1991 <br /> Mr.Karlin Knoll <br /> San Joaquin County Environmental Healthy <br /> P.O. Box 2009 MAR <br /> Stockton,CA. 95201 RNy1 2 � 1991 <br /> . f <br /> r, Re: Former Chevron S.S.#9-0342 PERM1 TISERS L TH <br /> VIH <br /> f 1347 S.'EI Dorado Street,Stockton,CA C <br /> Dear Mn Knoll: <br /> Enclosed is a quarter;y monitoring report dated February 22,.1991 which describes groundwater <br /> sampling by Chevron's consultant,Groundwater Techr_ology(GTI), on January 9, 1991 at the <br /> site referenced above. <br /> i Groundwater gradient,as calculated from`eater 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 frum 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 ground A-iter samples quarterly for one full year cvcle before deciding on the placement <br /> r of groundwater wells or BAT probes to further define the cztent of dissolved plhme hydrocarbons <br /> in the groundwater. <br /> By January 1992, tha gradient should he well defined and th-applicability of the BAT probe <br /> i sampling system should be well documented. <br /> ' ? If you have any questions or comments,plesse contact Mr.Clint Rogers at(415)842-8658. <br /> 1 <br /> Sincerely, <br /> Chevron U.S.A. <br /> S <br /> >3y <br /> Clint B.Rogers <br /> t Environmental Engi ear <br /> I Enclosure -- - - - - -- — , <br /> cc: Jim Maughan,Central Valle►,RWQCB,Sacramento,CA <br /> J Ramon Guerrero;>1327 S.Wilson Way,Stockton,CA 95205 <br /> Sandra Lindsey,GTI,Concord,CA <br />