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• <br /> WORK PLAN FOR INSTALLATION OF <br /> GROUNDWATER MONITORING WELL <br /> Stewart' s Beacon <br /> 515 West 11th Street <br /> Tracy, California <br /> 1. 0 INTRODUCTION <br /> In accordance with a request from Mr. William Stewart, Geological <br /> Audit Services, Inc. (GeoAudit) has prepared this work plan to <br /> install (1) additional groundwater monitoring well at 515 West 11th <br /> Street in Tracy, California (the site) . The location of the site <br /> is illustrated in Figure 1 . A plan of the site is illustrated in <br /> Figure 2 . <br /> 2 . 0 BACKGROUND <br /> 2. 1 Site Location <br /> The site is located in a relatively flat business and residential <br /> area of Tracy, California (Figure 1 - Location Map) . The site was <br /> • formerly a Beacon Gasoline Station. <br /> 2 .2 UST Removal <br /> Three underground storage tanks were removed from the site in 1988. <br /> Hydrocarbon contamination was discovered in the soil and <br /> groundwater following the tank removal , indicating that an <br /> unauthorized release of hydrocarbons had occurred. <br /> 2. 3 Soil Excavation <br /> In January 1990 the former tank pit was excavated to a depth of 14 <br /> feet. The excavation was dewatered and this water was placed in an <br /> 8, 000 gallon above ground storage tank. At some time prior to May <br /> 8, 1990, the tank pit was backfilled with the excavated soil to 7 <br /> feet below grade. Some time after May 1991, additional soil was <br /> imported to the site and used to backfill the excavation to surface <br /> grade. The water stored on-site in the 8, 000 gallon above ground <br /> tank was subsequently released to the area of the former <br /> excavation. <br /> 2.4 Groundwater Monitoring <br /> Three groundwater monitoring wells were installed on-site in June <br /> 1988 and a passive monitoring program was conducted between the <br /> second quarter of 1990 and the first quarter of 1991 (Figure 2 - <br /> Site Plan) . During the monitoring program, contamination levels <br /> showed considerable fluctuation with contamination directed <br /> Primarily to the north (monitoring well MW-1) . <br /> 1 <br />