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7hN3dwe11&Rd10 <br /> • Previous Investigations <br /> Numerous soil and groundwater investigations have been performed at Area 16 under the <br /> oversight of the SJCEHD. Up to 23 inches of free product was encountered in a groundwater <br /> monitoring well the immediate vicinity of the former UST in 1992. However,no free product <br /> has been found since 1996. Between 1990 and 1994, four groundwater monitoring wells and <br /> three soil borings were completed at the site (RESNA, 1991, 1994). In July 1995, sixteen soil <br /> probes were completed on and off site, with soil samples collected from five probes and <br /> groundwater from eleven (AGE, 1995). Five additional wells were installed in late 1995 (AGE, <br /> 1995). <br /> A soil vapor extraction and air sparging system was constructed in 1999 to mitigate the soil <br /> contamination and reportedly began operating in November 1999. The 7 February 2000 AGE <br /> Monitoring Report presents the general layout of the system and is included in.Appendix C. <br /> • Nine groundwater monitoring wells are currently being sampled for the owner as part of an <br /> ongoing groundwater monitoring program conducted under the oversight of the SJCEHD. <br /> Historical groundwater sampling data is included in Tables 2, 3, and 4 of the AGE 7 February <br /> 2000 Quarterly Report in Appendix C (AGE 2000b). <br /> Additional site investigation activities were performed by Treadwell &Rollo in August and <br /> September 1999, and reported in the 3 December 1999 Site Characterization Report. A <br /> geophysical survey was performed on 19 August 1999. No geophysical anomalies were <br /> encountered. <br /> On 21 September 1999, a geoprobe direct push rig was used to collect 15 soil and two grab <br /> groundwater samples. Soil borings 16B-1 through 1613-5 were pushed to depths ranging from 10 <br /> to 28 feet. Soil samples were retained in butyrate liners and covered with Teflon sheets and tight <br /> fitting plastic end caps. Soil samples were collected at the depths listed in Table 1 and shown on <br /> Figure 5. Analytical results are presented in Tables 1 through 4 of the report. Groundwater <br /> • samples were collected at borings 1613-3 and 1613-5. <br /> 13 <br /> 25970309.DGD 24 August 2000 <br />