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1 1.0 INTRODUCTION <br /> This report is being submitting on behalf of C. M. Weber Enterprises, <br /> Inc. to present the Remedial Action Plan (RAP) for groundwater <br /> impacted with petroleum hydrocarbons at the facility located at 141 <br /> North E1 Dorado Street in Stockton_, California (Figure 1). The <br /> project site is the future location of a fourteen story building <br /> which will be the beginning of the revitalization of downtown <br /> Stockton. The report provides background information, summarizes <br /> results of recent investigations, presents an evaluation of remedial <br /> alternatives, and outliner, a proposed remedial action plan for the <br /> impacted groundwater. <br /> 2.0 SITE BACKGR0UND <br /> In 1955, '.hell Oil Company constructed a retail gasoline and service <br /> facility at 141 North El Dorado Street in Stockton (Figure 2). This <br /> construction included the installation of four 4,000-gallon steel <br /> underground product storage tanks for the containment of leaded <br /> gasoline. One 500-gallon underground storage tank containing used- <br /> oil was also located on the property. In 1963, one of the leaded <br /> tanks was removed and two 7,500-gallon underg ound storage tanks were <br /> installed to store unleaded gasoline. The station discontinued <br /> r selling gasoline in 1981 and five of the product storage tanks were <br /> removed. No soil samples were cb'_lected and analysed at the time of <br /> 14 the tank removal. Following removal of the storage tanks, the tank <br /> pit excavation was backfilled and xepaved. The used-oil tank <br /> remained on site and was in use until Jana of 1990. <br /> a- 3.0 HXDROGEOLOGIC SETTING <br /> The site lies in the eastern portion of the Sacramento - San Joaquin <br /> Delta. The subsurface geology in the Stockton area is characterized <br /> by Pleistocene and Recent alluvial deposits. These alluvial deposits <br /> consist of heterogeneous sequences of sands and gravels originating <br /> from active stream channels, and silts and clays originating., from <br /> ` overbank and marsh depositional environments. <br /> According to the San Joaquin County Flood Control and Water <br /> Conservation District, Spring 1990, the regional groundwater gradient <br /> is to the east - northeast. <br /> The nearest surface water body to the site is the Stockton Deep Water <br /> Channel which trends east to west and is connected to the Sacramento <br /> San Joaquin Delta. The east end of the channel terminates just <br /> west of the site at Center Street. The site itself overlies the <br /> �- former east and of the channel. The site is also located <br /> ___approximately-_2.75_.miles.._south--of-.the_._.Calaveras River and 2.5 miles <br /> north of Walker Slough, a tributary of the San Joaquin River. <br /> A survey of all water wells within a one-mile radius of the site was <br /> conducted rased on information received from, the California <br /> ... Weber Point Property - 175 <br /> - H20RKP791.7LP - - <br />