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La WORK PLAN ARCO PRODUCTS COMPANY, STATION 2093 +� 3425 TRACY BOULEVARD TRACY, CALIFORNIA OCTOBER 10, 1988 `. This work plan has been prepared for ARCO Products Company (ARCO) Station 2093, located at 3425 Tracy Boulevard, Tracy, California (see Figure 1 for site location). This work plan will be submitted to ARCO; the California Regional Water Quality Control L,, Board, Central Valley Region (Regional Board); and the San Joaquin County Local Health District (County). The purpose of the work plan is to describe the proposed investigation of soil and groundwater quality at ARCO Station 2093. Three boreholes will be drilled L. and monitoring wells installed in each borehole to further define the lateral extent of contamination at the subject site. Underground utility services near the site are shown on Figure 2. No municipal wells'exist within 2,000 feet of the site. No wells are shown on the underground utility map provided by the City of Tracy_ However, it is possible that a water supply well that is no longer in use exists on the northeast corner of the site. As requested by ARCO, Brown and Caldwell (BC) proposes to determine the well's existence by use of a metal detector or other iron-finding device. If the well does exist, it will be properly abandoned by BC personnel. Before commencing work at the site, all necessary permits will be acquired. BACKGROUND Lo ARCO Station 2093 has been located at 3425 Tracy Boulevard, Tracy, since 1972. Prior to 1972, this relatively flat site was a vacant lot_ Lo In December 1986, a waste oil tank was excavated at this site. Soil samples taken from the excavation showed concentrations of gasoline significantly above designated levels LW established by the Regional Board in April 1986. The results of this investigation are included in BC's September 24, 1987, Problem Assessment Report. An Unauthorized Release Report was filed with the County indicating an unknown amount of spillage had occurred. In April 1987, as directed by the County, BC conducted a site investigation at the +.• subject site. This investigation included the drilling of four boreholes with the installation of groundwater monitoring wells in each borehole. Analytical results from this investiga- tion indicate contamination in soil and groundwater beneath the site. Table 1 shows �. analytical results of soil samples taken during the April 1987 site investigation. Table 2 summarizes analytical results of groundwater samples taken on a quarterly basis from the wells at the site.