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MONITORING WELL INSTALLATION WORKPLAN WESTERN LIFT 3430 S. El Dorado Street BACKGROUND The site is located in a flat industrial area south of Stockton (Figure 1 - Location Map, 7. 5 Minute Stockton West Quadrangle, USGS Topographic Map Series, 1976) . The facility consists of a large warehouse and adjoining office and exterior fenced parking/delivery area (Figure 2 - Site Plan) . Three underground tanks were removed from the delivery area in June of 1991. Gasoline contamination was detected in three of the seven soil samples collected from the excavation, indicating that an unauthorized release of hydrocarbons had occurred and that an assessment of the site was required. Sample results were summarized in the Site Contamination Workplan submitted by Geological Audit Services to San Joaquin County Environmental Health Division on July 24, 1991. The assessment of the site was performed in two phases. Each phase consisted of overexcavation followed by the collection and analysis of soil samples from the walls and floor of the excavation. The excavation phases and sampling are described in the Preliminary Investigation and Evaluation Report (PIER) submitted to the SJEHD on 11 December 1991. On 1 May 1992, backfilling of the excavation was completed. The excavation was backfilled to grade with pea gravel and will be covered with asphalt to match the surrounding surface. PROPOSED WELL LOCATIONS Data obtained from an ERM-West report on the Manna Pro facility, located immediately south of the site, shows a northerly groundwater gradient. Groundwater in the area is expected to be at 40 feet below surface grade, according to the report. Using the data obtained from the ERM-West report, we feel that one monitoring well, installed in a down gradient direction, will be sufficient to determine if any contamination of the groundwater has occurred as the result of the operation of UST's on the property. We propose to install one monitoring well immediately north of the excavation to determine if groundwater contamination is present beneath the property (see Figure 2 - Site Plan) .