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i <br /> 19 October 2012 <br /> AGE-NC Project No. 97-03.12 <br /> Page 21 of 22 <br /> 8.0. CONCLUSIONS <br /> Based upon the results of the groundwater. monitoring, AGE presents the following <br /> conclusions: <br /> • Depth to water remained stable across the site during the seasonal dry months of <br /> September and November 2011. The depth to groundwater has ranged from <br /> approximately 80 feet bsg to 40 feet bsg. <br /> • The vertical and horizontal extent of dissolved TPH-d, TPH-g and benzene in <br /> groundwater has been defined based on data from historical monitoring events. <br /> • 1,2-DCA concentrations reported in well MW-5 were generally consistent with <br /> historical trends. Trend graphs of the groundwater elevation and analytical results <br /> are depicted in Appendix D. Natural attention is ongoing at the site and will likely <br /> remediate the threat of the residual adsorbed petroleum and dissolved 1,2-DCA. <br /> Currently no structures are located within a distance of the shallow petroleum soil <br /> impact which justifies soil vapor intrusion mitigation. <br /> t 9.0. RECOMMENDATIONS <br /> L <br /> Based on the results of this andrevious investigations, AGE recommends: <br /> p g <br /> • Consideration of the site for low-risk closure, based on the stable dissolved <br /> hydrocarbon concentrations (lack of, concentrations) and declining dissolved <br /> 1,2-DCA concentrations. <br /> • AGE recommends that no further action be taken in regard to the remaining <br /> petroleum-impacted soil. <br /> A recommendation for well destructions is included with site closure. <br /> r <br /> l.� <br /> Advanced GeoEnvironmental,Inc. <br /> I <br /> I <br /> I <br /> i <br />