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Smith Environmental FACILITY BACKGROUND SITE SAFETY PLAN On September 6, 1989, three underground gasoline storage tanks were removed at the project site by Western Meter Service of Stockton, California. Soil samples were collected beneath each tank and the associated piping. Soil samples collected from beneath two of the tanks contained moderate to high levels of ethyl benzene and xylenes (1.2 to 70 parts per million [ppm]) as well as total petroleum hydrocarbons as gasoline (TPHg), at 470-830 ppm. Due to the presence of elevated concentrations of petroleum hydrocarbons in the tank pit soil samples, further investigation was required by San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD). In a two -phased approach beginning on November 1, 1990, RESNA Industries, Inc. (RESNA) personnel advanced six soil borings (MW 1-MW6) to depths ranging from 27 to 30 feet below grade at the project site to accomplish the following: 1) define the lateral and vertical extent of hydrocarbon impacted soils; 2) determine soil stratigraphy; and 3) install groundwater monitoring wells within the uppermost aquifer in order to assess groundwater quality. The boring/well locations are plotted on Figure 2. Field methodology and analytical results are discussed in detail in RESNA's Interim Problem Assessment Report, dated January 13, 1992. At the request of PHS/EHD RESNA Industries prepared and submitted a Soil Remediation Workplan dated July 22, 1992. Soil excavation was proposed the soil remediation method for the site. In correspondence August 17, 1992, PHS/EHD concurred excavation of hydrocarbon contaminated soil was the preferred method of remediation The site's station building and garage were demolished in December 1994, in part to facilitate the removal of hydrocarbon contaminated soil which is suspected beneath the station building. The demolition of the station building was requested in PHS/EHD correspondence dated July 7, 1994. A required demolition asbestos survey conducted previously on the station building, determined the presence of asbestos containing materials. E. T. Abatement, of Modesto California, properly removed and disposed of the site's suspected asbestos containing materials on November 11, 1994. On February 14 through 17, 1995, approximately 1,400 cubic yards of soil were excavated from the vicinity of the former underground fuel storage tanks. The extent of the excavation is depicted on Figure 2. Analytical results of excavation confirmation samples indicate that the majority of impacted soil has been removed from the southern, southwestern, and eastern portions of the excavation. Field observations indicated contamination along eastern portion of the northern sidewall appeared to be limited to the saturated zone. The northwest portion of the excavation was obviously discolored and impacted above and below the water table, however due PAGE 3