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MONITORING WELL INSTALLATION <br /> WESTERN LIFT <br /> 3430 S. El Dorado Street <br /> BACKGROUND <br /> The site is located in a flat industrial area south of Stockton <br /> (Figure 1 - Location Map, 7 . 5 Minute Stockton West Quadrangle, USGS <br /> Topographic Map Series, 1976) . The facility consists of a large <br /> warehouse and adjoining office, and exterior fenced <br /> parking/delivery area (Figure 2 - Site Plan) . <br /> Three underground tanks were removed from the delivery area in June <br /> of 1991. Gasoline contamination was detected in three of the seven <br /> soil samples collected from the excavation, indicating that an <br /> unauthorized release of hydrocarbons had occurred and that an j <br /> assessment of the site was required. Sample results were summarized <br /> in, the Site Contamination Workplan submitted by GeoAudit to San <br /> Joaquin County Environmental Health Division on 24 July 1991. <br /> The assessment of the site was performed in two phases. Each phase <br /> consisted of overexcavation followed by the collection and analysis <br /> . of soil samples from the walls and floor of the excavation. The <br /> excavation phases and sampling are described in the Preliminary <br /> Investigation and Evaluation Report (PIER) submitted to the SJEHD <br /> on 11 December 1991. <br /> On 1 May 1992 , backfilling of the excavation was completed. The <br /> excavation was backfilled to grade with pea gravel and will be <br /> covered with asphalt to match the surrounding surface. <br /> PROCEDURES <br /> On 1 June 1992, one monitoring well was installed immediately north <br /> of the former tank excavation. This location is in the down- <br /> gradient direction from the former tanks (see Figure 2 - Site <br /> Plan) . <br /> The boring was advanced to a depth of 54 . 5 feet using a truck <br /> mounted 8-inch hollow-stem auger rig. The Acker AD-2 drill rig and <br /> two man crew were supplied by West Hazmat Drilling Corporation. <br /> Discrete soil samples were collected ahead of the drill bit using <br /> a split-tube sampler loaded with three pre-cleaned 2 . 5 by 6 inch <br /> brass tubes. The samples were obtained at five foot intervals. To <br /> avoid cross contamination, the sampling equipment was washed in a <br /> tri-sodium phosphate (TSP) solution and rinsed twice with water <br /> . prior to each sampling run. <br /> For each sample, both ends of the lead tube were then covered with <br /> aluminum sheets, capped and sealed with tape. The samples were <br /> stored on ice pending transmission to a state certified laboratory <br />