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LtNU.mdp,p„ Close out parr„dre Evans GMsubarvan, Aho,2017 Lisslikepill The fact that Mere was no rebound of Vt%s in ground water above the MCL cleanup standards in ever five yeah of monitoring fallowing treatment system shutdown, and Mat VOC concentrations nued to decrease towards reporting limitsduring this time, provides rurther evidence Mat the debris burial trenches are not a signifcant continuing source of VOCs to Eastern GSA ground water. No unacceptable risk or named was identified far ecological receptors in Me baseline risk ant for Me Eastern USA Suarea.b assessment 1995, a Feasibility Study Mr the GSA OU that evaluated remedial alternatives for cleanup s sued. A Proposed Plan for Envirvmncntal Cleanup of the USA OU was issued in 1996 for the public to review and comment on the remedial alternatives and proposed cleanup remedy and standards. As discussed in Seution 2.1 above and presented in Appendix A, DOEII.LNL conducted additional characterization a SVOCSIPAHs and PCBs in subsurface soil and SVOCs in ground water in MCI stern GSA debris burial trenches area in Ml 4. Because SVOCs or PAHs were not deteckd in any of the soil or ground water samples tattersall in the Pamem GSA debris burial trench area above the reporting bonus, DOE and the regulatory agencies agreed that the re cstimsion of SVOCs and PAI Is in Me Memo GSA debris burial =rich area was complete, and no further action for these anstionams was needed. 'rho PCB analytical data for samples collected in the Eastern USA debris burial trench area indicate Mat: While PCPs were detected above Me analytical repented limit in some mil samples, were below CPA's residential and industrial mil Regional Screening Levels and the MCL-bead Protection of Ground Water Soil Screening Levels. Therefore, these a t rnts do not pose an unacceptable risk or impact to ground water above MCLs. The lateral and vertical extent of PCBs in subsurface suit is bounded by non-detections, or evidence of native material. PCBs were not detected above the reporting limits in any ground water samples collected Real wells located near and/or do negmdit nt from the boreholes in which Me PCBs were detected. Therefore, DOE and the riegulakry agencies agreed that the investigation of PCHs in the Eastern USA debris burial trench area was complete, and no further action for these constituents was needed. 2.4. Record of Decision In January 19972 the U.S. DOE, EPA, DISC, and the RWQCB signed a ROD in which the final remedial action and cleanup standards were saleckd Mr the GSA OU (U.S. DOE, 1997). The selected remedy fiu the Eastem GSA consisted of: I) Monituring ground water to evaluate the elTectivemss ofthe remedy in achieving cleanup standards, and to ensure Men: is no impact to downgns lent water-supply wells. 2) Institutionabland use amends to prevent human exposure to communication and to market Me integrity ofthe remedy.