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Working To Restore Nature <br /> 1TAL HVAI I'l - <br /> 3164 Gold Camp Drive � 1 .� ll ? <br /> Rancho Cordova, CA 95670 . <br /> Phone: (916)852-6690 + <br /> Fax: (916)852-6688 ,moi <br /> November 10, 1992 <br /> Mr..Kenneth R. Earnest <br /> Ultramar, Inc. <br /> 525 West Third Street <br /> Hanford-, California 93230 <br /> Subject: . Results of Investigation and Recommendations-.for;Closure at'Beacon Service <br /> Station.No. 492, 470 North Main Street, Manteca; California., <br /> Mr. Earnest: <br /> At the request of Ultramar,-.Inc.,'RESNA Industries (RESNA) conducted an environmental <br /> " investigation at the subject site (Plate 1).'.Our most recent work conducted•in October 1992 <br /> included drilling confirmation borings and collecting: soil-samples.:as outlined in the <br /> addendum to our,Work Plan.No:'-86102=9%.dated July,27; 1992. The purpose.of the,work <br /> was.to.evaluate whether residual hydrocarbonsin soil near.'theproduct tanks have'-bee.n- <br /> remediated by vapor .extraction:' <br /> BACKGROUND <br /> In December 1986,RESNA conducted a subsurface investigation that included drilling three <br /> soil borings and-.installing three monitoring wells !at the site (Plate 2).. Results of that <br /> investigation indicated residual gasoline hydrocarbons were detected in soil'and water near <br /> the tank cavity. -.Benzene.concentrations:in ground-water-simples-from these .wells were. <br /> .above 1.0 part per billion.. Because.residual hydrocarbons were detected in soil near the <br /> tank cavity, in October 1988,RESNA observed the installation of four vapor-extraction wells <br /> near the tank cavity. According.to Ultramar personnel,�EVAX Technologies, Inc:conducted <br /> vapor extraction at the site from October.13 through November.17, 1989, and extracted and' <br /> treated over 2,100 pounds: of hydrocatboris.` To:assess the soil and` ground water � <br /> downgradient from.the tank cavity, 'installation -of an additional :.monitoring 'well was <br /> requested by San Joaquin County Public Health Services, Environmental Health.Division, <br /> in their.;letter of April 18,. 1991. <br /> 86102-9 <br /> 1029kear <br />