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` Former Beacon Station No. 12474 March 18,2002 Stockton California Problem Assessment Report/Corrective Action Pian groundwater. The corrective action plan portion of this report presents site remedial • objectives for gasoline hydrocarbons, and technically and economically feasible remedial alternatives for soil and groundwater to protect potential beneficial uses of groundwater beneath the site. 2.0 SITE DESCRIPTION AND PREVIOUS INVESTIGATIONS The site is an operating gasoline service station located on the southwestern comer of the intersection of East Main Street and Broadway Avenue in Stockton, California, as shown on Figure 2. Site facilities include a station building, two gasoline product dispenser islands, and three underground gasoline storage tanks (USTs). The essentially level site is situated at approximately 28 feet mean sea level in Section 7, Township I North, Range 7 East, Mount Diablo Baseline and Meridian. The regional topography slopes gently westward. . Previous environmental investigations at the site have been performed by Acton, Mickelson, van Dam, Inc. (1995), El Dorado Environmental Inc. (1997), and Horizon (1996, 1997a, 1997b, 2000a, 2000b). Three soil borings (SB-1 through SB-3) were advanced priorto removal of the UST's. The UST's were removed and replaced in September 1993. In December 1993, three additional soil borings were advanced and converted to groundwater monitoring wells (MW-1 through MW-3). In May 1996, Horizon advanced soil borings B-1 through B-4 and installed two off-site groundwater monitoring wells (MW-4 and MW-5). Soil analytical data for soil borings B-1 through B-4, and monitoring wells MW-4 and MW- 5 are contained in Appendix A. In September 1997, Horizon advanced six soil borings at the site (Horizon, 1997b). Three of the soil borings were located adjacent to monitoring wells MW-1, MW-2 and MW-3 and were completed as monitoring wells MW-6, MW-8, and MW-9. The wells were constructed with shallower and slightly overlapping screened intervals because of rising groundwater . levels. One soil boring was completed as monitoring well MW-7 located in the southeast 474PARCAP3-02.doe 2 Project No. 1474.23 HORIZON ENVIRONMENTAL INC.