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ERI <br /> ENVIRONMENTAL RESOLUTIONS, INC. <br /> March 28, 1997 <br /> ERI 205503.WOl <br /> Mr. Adadu Yemane ( � <br /> 76 Products Company" n <br /> 2000 Crow Canyon Place, Suite 400 �� 1 <br /> San Ramon, California 94583 <br /> Subject: Work Plan for Supplemental Environmental Investigation at Unocal Service Station <br /> 5886, 2701 March Lane, Stockton, California. <br /> Mr. Yemane: <br /> At the request of 76 Products Company, Environmental Resolutions, Inc. (ERI) is submitting this <br /> work plan describing the tasks to evaluate the source of hydrocarbons and further evaluate soil and <br /> groundwater conditions at Unocal Service Station 5886 in Stockton, California. The purpose of the <br /> work is to evaluate the integrity of the existing underground fuel delivery system, the source of <br /> methyl tert-butyl ether (MTBE) in groundwater, and evaluate the lateral extent of residual and <br /> dissolved MTBE in soil and groundwater. The San Joaquin County Public Health Services <br /> Department, Environmental Health Division requested 76 Products Company submit a plan to <br /> investigate and abate any potential, suspected, or known discharges of hazardous materials including <br /> petroleum hydrocarbons and delineate the extent of MTBE detected beneath the subject site. <br /> Work for the investigation includes: 1) obtaining and reviewing MTBE data from a previous <br /> investigation and fuel inventory reconciliation records; 2) obtaining appropriate well permits and <br /> drilling four on-site soil borings; collecting soil samples; constructing groundwater monitoring wells <br /> in these borings; developing and purging the new wells; collecting groundwater samples; analyzing <br /> selected soil and groundwater samples; and 3) interpreting the data to evaluate the source and extent <br /> of residual hydrocarbons in soil and lateral extent of dissolved MTBE in groundwater, and preparing <br /> a report. <br /> BACKGROUND <br /> The site is immediately west of Interstate I-5 on the northwestern corner of March Lane and the I-5 <br /> offramp in Stockton, California, as shown on the Site Vicinity Map (Plate 1). The locations of <br /> existing underground storage tanks (USTs), dispenser islands, and other selected site features are <br /> shown on the Generalized Site Plan (Plate 2). Properties in the vicinity of the site are generally <br /> occupied by commercial developments. <br /> Unocal Corporation purchased the land in 1967, at which time the property was vacant. In 1982, <br /> Unocal constructed a service station at the site and installed three 12,000-gallon underground storage <br /> tanks (UST's) used to store gasoline and diesel fuels (Delta Environmental, February 6, 1996). <br /> Between July 1995 and September 1996, Unocal replaced the original UST's and associated product <br /> distribution lines, enlarged the existing tank pit to accommodate three new 15,000-gallon UST's, <br /> 74 Digital Drive, Suite 6, Novato, California 94949 415.382-9105 (FAX 415-382.1856) <br /> Irvine • Novato • Seattle <br />