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L <br /> A plied GeoSyeteM$,fic. <br /> A RESNA Company <br /> Environmental Solutions <br /> Through Applied Science, <br /> 4A.W1 3164 Gold Camp Drive, Suite 200 Engineering&Construction <br /> Rancho Cordova, CA 95670 <br /> Phone (916) 852-6690 <br /> FAX (916) 852-6688 <br /> .• June 2, 1992 <br /> Mr. Kenneth R. Earnest <br /> Ultramar, Inc. <br /> 525 West Third Street <br /> Hanford, California 93230 <br /> Subject: Status of Environmental Investigation and Ground-Water Monitoring, First <br /> Quarter 1992, for Beacon Service Station No. 492, 470 North Main Street, <br /> Manteca, California. <br /> 4. <br /> Mr. Earnest: <br /> RESNA Industries (RESNA) is reporting on the status of work conducted during the first <br /> quarter 1992 at the request of Ultramar, Inc. at the subject site (shown on Plate 1). Work <br /> >r included conducting a well search, drilling one soil boring and installing groundwater <br /> monitoring well MW-4, and monitoring the ground water in wells MW-1 through MW-4. <br /> LW The purpose of this work was to assess soil and ground water northeast of the tank cavity <br /> for hydrocarbons and to evaluate the ground-water gradient. The approximate locations of <br /> the former tanks and other selected site features are shown on Plate 2. According to <br /> information provided by Ultramar, gasoline and diesel have been dispensed at this site. <br /> BACKGROUND <br /> In December 1986, RESNA (formerly Applied GeoSystems) conducted a subsurface <br /> investigation that included-drilling three soil borings and installing three monitoring wells <br /> at the site. Soil and water samples were collected and submitted for laboratory analyses. <br /> Results of that investigation indicated gasoline hydrocarbons were detected in soil and water <br /> near the tank cavity. Benzene concentrations in ground-water samples from these borings <br /> were above 1.0 part per billion. On this basis, we began quarterly monitoring of the ground <br /> water underlying the site. 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 remediation at the site from October 13 through November 17, 1989, and <br /> extracted and treated over 2,140 pounds of hydrocarbons. To assess the soil and ground <br /> A0 water downgradient of the tank cavity, a well search and installation of the additional <br /> monitoring well were requested by San Joaquin County Public Health Services, <br /> Environmental Health Division, in their letter of April 18, 1991. <br /> Iwo <br /> 0316kear <br /> 86102-7 <br /> i.. <br />