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�.., Fire Station No. 12 TL A68105.01 March 10, 1995 Page 3 .,., 3.3 Project HistQa Twining understands that a 550-gallon diesel UST and a 550-gallon unleaded gasoline UST were removed from the site in September 1994. According to information provided by the City of Stockton, initial soil analyses conducted following removal of the USTs detected unsatisfactory concentrations of petroleum product constituents. Subsequently, limited overexcavation of the UST pit was conducted and soil samples were collected from the base and walls of the excavation. Soil sample analytical results for the soil samples collected following overexcavation activities are summarized in Table 1. TABLE 1 SUMMARY OF SOIL SAMPLE ANALYTICAL RESULTS Analytical results are in parts per million Soil sample depths were not presented in the laboratory report Total Soil Sample TPH-G B T E X Lead V BS-1 <1.0 0.005 0.012 0.005 0.059 NA EW <1.0 <0.005 <0.005 <0.005 <0.005 NA SW 1.4 <0.005 0.007 <0.005 0.051 NA NW 6.6 <0.005 0.037 0.045 0.48 NA WW <1.0 <0.005 <0.005 <0.005 <0.005 NA SP-1-2 20 0.014 0.062 0.093 OSO 31 Notes: NA = Not analyzed TPH-D = Total petroleum hydrocarbons as diesel TPH-d = Total petroleum hydrocarbons as gasoline BTEX = Benzene,toluene,ethylbenzene,and total xylenes �. 4.0 PROPOSED FIELD ACTIVITIES Proposed field activities are summarized in the following subsections. Standard operating procedures (SOPS), relevant to the field activities, are described in Appendix A. 4.1 Soil Borings Twining proposes to drill four soil borings in and around the former UST pit using a CME- 75 truck-mounted drill rig equipped with 6-5/8-inch diameter hollow-stem augers. Initially, the one soil boring will be drilled through the center of the former UST pit to assess the vertical extent of PPC-containing soils. The depth of this boring will be based on field L