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6.0 SPECIFIC INFORMATION FOR CLOSURE REQUEST <br /> 61 Introduction <br /> This section provides information specifically required for closure review as per the October 7, 1993 <br /> Addendum to Appendix A of the Tri-Regional Recommendations A case closure checklist in included <br /> in Appendix F <br /> 6.2 Rationale for Closure <br /> Based on the analytical results of the soil samples collected from the soil bonngs and the single <br /> petroleum hydrocarbon detected during four quarters of groundwater monitoring and sampling, <br /> any remaining petroleum impacted soil does not appear to be a threat to groundwater. The <br /> t majority of the contaminated soil was removed in July 1993 and remeduated to nondetectable <br /> levels The remaining quantity of impacted soil was relatively small, 220 cubic yards, and the <br /> concentrations of petroleum hydrocarbon contamination were low, except for one floor <br /> sample. Natural biodegradation will reduce the quantity of contaminated soil and the <br /> concentrations of petroleum hydrocarbon contaminants over time <br /> 1 6.3 Site-Specific Information Summary <br /> o A well search was not conducted for thus site <br /> o Depicted on enclosed figures are the site location and nearby surface waters(Figure 1), <br /> the site to scale and former tank locations (Figures 2 and 4), well and boring locations <br /> (Figure 2), most recent groundwater gradient contours (Figure 3), and the excavation <br /> area/former area of impaction in the soul(Figures 4 and 7) <br /> ' o Water level data arep resented In Table 1 During the investigative history of the site, <br /> depth to groundwater has ranged from 12 15 to 16 68 feet below grade <br /> the soil analytical results and Table 2 resents the <br /> o Tables 3, 4, and 5 present yt p <br /> 1 groundwater analytical results <br /> o Soul remediation methodology is described In Section 4 5 Remedial Actions Natural <br /> biodegradation and aeration were used to remove petroleum hydrocarbons from the <br /> excavated soul which remains stored on-site <br /> o No subsurface groundwater remediation system has been recommended or installed <br /> Approximately 7,500 gallons of groundwater was removed and surface discharged <br /> Ttus work was associated with excavation activities Historically, groundwater had not <br /> been impacted by the former petroleum hydrocarbons in soil <br /> w W43371closure doe 6 <br /> SMTH <br /> 1 <br />