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11 December 1991 <br /> GeoAudit CV45-49C5-1. 10 <br /> ' Page 1 of 3 <br /> PRELIMINARY EVALUATION AND INVESTIGATION <br /> tOF HYDROCARBON CONTAMINATION <br /> WESTERN LIFT <br /> t 3430 S. E1 Dorado St. <br /> Stockton, CA <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 parking/delivery <br /> areas. <br /> ' The site is underlain by unconsolidated Quaternary alluvial <br /> sediment. The depth to groundwater is greater than 35 ft, which is <br /> the depth of the present excavation. <br /> Three underground tanks were removed from the delivery area by <br /> Frahm Construction on June 6, 1991. Gasoline contamination was <br /> ' detected in three of the seven soil samples collected from the <br /> excavation, indicating that an unauthorized release of hydrocarbons <br /> had occurred and that an assessment of the site was required. <br /> ' Sample results were summarized in the Site Contamination Workplan <br /> submitted by Geological Audit Services to San Joaquin County <br /> Environmental Health Division on July 24 , 1991. <br /> The workplan submitted by our office to overexcavate the <br /> contaminated soil was approved by Mr. Harlin Knoll of San Joaquin <br /> EHD. A 30-day public comment period followed submittal of the <br /> ' workplan; this comment period expired on September 15, 1991 and <br /> work began on September 16. <br /> ' PROCEDURES <br /> The assessment was performed in two phases. Each phase consisted of <br /> overexcavation followed by the collection and analysis of soil <br /> samples from the walls and floor of the excavation. <br /> Excavation was performed by representatives of Falcon Energy using <br /> an excavator. Excavated soil was stockpiled on site in accordance <br /> ' with the workplan, and contaminated soil was separated from non- <br /> contaminated soil. A staff geologist from Geological Audit was on <br /> site during the excavation and periodically monitored excavated <br /> soil for hydrocarbon contamination visually and with a hand--held <br /> Organic Vapor Meter. <br /> 1 <br />