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I C <br /> November 1990 -3- M88168D l <br /> contamination appeared to be limited to the southwest corner of the excavation. <br /> The analytical results of the ground water samples collected by SGD from the <br /> domestic water wells at the site at that time indicated that ground water did not <br /> contain hydrocarbon contamination above regulatory action levels. <br /> SGD implemented a site remediation program in January 1990, which was <br /> documented by SGD letter-report, Environmental Services, Site Remediation, Color <br /> Soot Lodi, Inc. , February 1990. Contaminated soils were excavated, removed, and <br /> disposed of off-site. As the soil was being removed, it was visually and <br /> oifactorally monitored, as well as monitored with a PID. After all obviously <br /> contaminated soil (by sight, smell, or PID reading) had been removed from the <br /> excavation, an additional 5 feet of soil was removed from the walls and floor to <br /> ensure complete remediation. Following the removal of the soil, confirmatory <br /> i <br /> soil samples were collected from the walls and floor of the excavation. <br /> J <br /> Analytical data obtained from the samples exhibited only trace concentrations of <br /> toluene and xylenes at concentrations well below regulatory action levels. <br /> Additionally at this time ground water samples were once again <br /> ~° collected from the domestic water wells within a 500-foot radius of the site. <br /> Analytical data obtained from the ground water samples indicated that the ground <br /> water in the wells did not contain hydrocarbon contamination above State of <br /> California drinking water standards (DWS) at that time. Trace concentrations of <br /> benzene were found in all four wells which were sampled. <br /> I <br /> METHODS OF INVESTIGATION <br /> Advancement of Drill Holes/Installation of Ground Water Monitoring <br /> Well. On October 8 and 9, 1990, four drill holes were advanced to depths ranging <br /> from 30 to 90 feet bgs. All four drill holes were advanced by Western Strata <br /> Exploration of West Sacramento, California (refer to Figure 2 - Site Plan, for <br /> locations) . All drill holes were geologically logged and the soil monitored with <br /> a photoionization detector (PID) by an SGD staff geologist. One of the drill <br /> holes (MW-1) was completed as a ground water monitoring well. The drill hole <br /> logs are presented in Appendix A, and the drilling procedures are described in <br /> l <br />