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4 <br /> SECOR www.secor.com <br /> INTERNATIONAL 3017 Kilgore Road,Suite 100 <br /> S E C O R INCORPORATED Rancho Cordova,CA 95670 <br /> 916-861-0400 TEL <br /> 916-861-0430 FAX <br /> June 26, 2003 X�~ ' <br /> Z _w <br /> Ms. Victoria McCartney <br /> San Joaquin County Environmental Health Department <br /> 304 East Weber Avenue, Third Floor <br /> Stockton, California 95202 t ' <br /> RE: Aquifer Test Report and Work Plan for Interim Remedial Measure ' <br /> Chevron Service Station 9-1452 ri <br /> 334 East Main Street <br /> Ripon, California l <br /> Site Code 1665 <br /> SECOR Project No.: 77CH.91452.01.0170 <br /> Dear Ms. McCartney: <br /> SECOR International Incorporated (SECOR), on behalf of Chevron Environmental Management <br /> Company (Chevron), presents this report of aquifer testing performed at the above-referenced site <br /> (Figure 1). These activities were undertaken to assess the sustainable yield of the pumping well <br /> (MW-8), the impact of pumping on dissolved hydrocarbons in groundwater beneath the site, and to <br /> evaluate the aquifer characteristics. This work was done in accordance with SECOR's Site <br /> Assessment Report and Work Plan for Further Assessment(work plan), dated June 11, 2002. The <br /> work plan was approved by the San Joaquin County Environmental Health Division in a letter dated <br /> July 1, 2002. CPT and drilling activities proposed in the work plan were described in SECOR's CPT <br /> and Monitoring Well Installation Report, dated February 28, 2003. In addition to the results of aquifer <br /> testing performed at the site, SECOR proposes the periodic extraction of groundwater from MW-8 as <br /> an interim measure to remove dissolved methyl tertiary butyl ether (MtBE) in groundwater near the <br /> underground storage tank (UST) complex at the site. <br /> SITE BACKGROUND <br /> The site is an active service station located at 334 East Main Street in Ripon, California. Current site <br /> facilities include three 12,000-gallon gasoline USTs, two dispenser islands under a common canopy, <br /> and a station building containing two hydraulic hoists. <br /> WELL DEVELOPMENT <br /> On March 31, 2003, SECOR developed groundwater monitoring/extraction well MW-8. The well was <br /> first developed using a PVC bailer to remove silt and sand accumulated at the bottom of the new <br /> well. After removing most of the silt and sand, the well was further developed using a submersible <br /> pump. The pump was lowered into the well and groundwater was pumped until the development <br /> parameters, including electrical conductivity, temperature, and pH, were stabilized and relatively non- <br /> turbid water was observed leaving the well. Approximately 620 gallons of groundwater were <br /> removed during development. <br /> Jtff'GROUNDWATER SAMPLING AND ANALYSIS <br /> Groundwater sampleswere collected from a sample port on the discharge pipe of the submersible <br /> pump in MW-8 on April 31, 2003, after development of the well, and on April 3, 2003, at the <br /> conclusion of the constant-discharge pumping test. These samples were analyzed for total <br /> I:\Chevron\91452\REPORTS\Aquifer Test Report and Plan for Interim Remedial Measure.doc <br />