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0 <br /> 1Weadwell&Rolb <br /> Previous Investigations <br /> A significant amount of soil and groundwater investigation work has been performed at Area 15, <br /> under the oversight of the SJCEHD. Underground storage tanks (USTs)which reportedly stored <br /> gasoline, diesel, and trichloroethane (TCA) were formerly located in three areas of the site. The <br /> USTs were removed in 1986 (four tanks) and 1992 (three tanks), and petroleum hydrocarbon <br /> contamination has been documented(AGE 1997). TCA has been detected in soil and <br /> groundwater from the area of the former TCA tank(AGE 1999a). Seventeen Geoprobe borings <br /> were completed around the former UST locations in 1995. Soil samples were generally collected <br /> at 5-foot intervals beginning at 10 feet bgs, and groundwater samples were collected from six <br /> geoprobes. There are currently 15 groundwater wells being monitored as part of an ongoing <br /> groundwater monitoring program conducted under the oversight of the SJCEHD. This includes <br /> 3 wells monitoring upper and lower saturated zones (wells 19, 20, 21). Historical groundwater <br /> sampling data is included in Tables 2, 3, and 4 of the AGE 7 February 2000 Quarterly Report in <br /> Appendix C (AGE 2000a). No soil or groundwater remediation efforts are currently in progress <br /> at this site. <br /> Additional soil and groundwater sampling was performed by Treadwell & Rollo in 1999. On 19 <br /> August 1999, Treadwell &Rollo conducted a geophysical survey at Area 15. The investigation <br /> area was divided into three separate areas using 10-foot grid spacing where possible. The <br /> interior of buildings was not surveyed. Geophysical anomalies that may be associated with <br /> buried metal objects were encountered. <br /> On 20 and 21 September 1999,Treadwell&Rollo collected sixteen soil and two grab <br /> groundwater samples. Soil borings 1513-1 through 15B-5 were advanced to depths ranging from <br /> 10 to 26 feet bgs, at the locations shown.on Figure 4. Analytical results for soil are presented in <br /> Tables 1 through 4. Groundwater grab sampling was performed on borings 1513-5 and 15B-8 <br /> and the analytical results for groundwater are presented in Tables 5, 6, and 7. <br /> 11 <br /> 25970309x.DGD 24 August 2000 <br />