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' 1 ) Ox(. 4R-4ar0„ Ome (ovReyniforaheEmenGbnaba.rair, Amy2017 UNL.me 300 Eastern GSA Subareas, but only the Eastern GSA portion of the DO is relevant to and will be discussed in this report. The afisite area directly adjacent to the Eastern GSA is privately owned much land. Evidence ofachcmical release to ground water in the OSA was first discovered in 1982 when trichloroethylene CWE) was detested in Well '1, a formoonsite Site 300 wafter-supply well located n the Central GSA. Further investigations led to the discovery and investigation Of several onber release areas in the USA, including the debris burial trenches in the Eastern GSA. In the Pacts and 1970, volatile organic compound (VOC)-contaminated debris was buried in trenches located in the Eastern USA causing VOC consummation of ground water and subsurface mil. In 1991, ground water extraction and treatment began in the Eastern GSA as a not-time-critical removal action. In June 1992, EPA, DTSC and RWQCB, and DOE signed a Federal Facility Agreement(FFA) for th"Immup ofLLHL Site 300. The Site-Wide Remedial Investigation union (Webster-Scholten, 19") was issued in 19942 followed by the Feasibility Study for the GSA DO 1996) 5 An OU-pecifi cROD ford plan r Environmental n the GSADOwassigned in January 1992 (U.S. DOGU OE, 199J) The Remedial Design for the GSA Oil was issued in 1998 (Rueth et al., 1998). Remedial action nstruction ompletion was documented mJune 2015. 'Ihe EPA performed a cunsfrvclien complmtion inspection on July 13, 2005. Five-Year Reviews wore completed in 2001 (Emy at al., 2001), 20M (Dibley at al., 2006), and 2011 (Valent at al., 2011). The DOOR Fouts Five-Year rew ed s submitt to the regulators on June 22, 2016. Remediatien efforls in the Eastern GSA have successfully reduced concentrations of VOCS in ground water to below the cleanup standards act in the GSA ROD, and the Eastern GSA ground re restraction treatment system w shut Off on February 15, 2002 with regulatory approval. Asrequiredby the GSA ROD, ground water monitoring was conducted for rive years after shutdown to determine if VOC concentrations would rise or "rebound" above cleanup standards. The results ofthe monitoing, that indicated that VOC concentrations had remained below clearing iandards it the five-year post shutdown monitoring period, were im seined a the February 24, 2012 Remedial "cct Manager's (RpW Meeting. The regulatory agencies agreed that cleanup Of the Eastern GSA was complete, monitoring and reporting could cease, and that close out documentation should be submitted (Ferry and Holtzapple, 2012). In December 2012, DOE submitted the "Draft Close Out Report for the Eastern GSA Subarea ofOU 1" (Dibley and Perry, 2012) to document completion ofmanediation. Regulatory comments on the draft report were addressed and WE submitted the draft final regard is June 2013. At the July 18, 2013 RPM Meeting, the new EPA and the RWQCB RPMs indicated that they tell that them were dean gaps for se ivolatile organic compounds (SVOCsb polycyclic a c hydmcarbn ns (PAHs) and polychlorinated biphenyls (PCBs) in subsurface soil in the vicinity Of thedebris burial trenches thatneeded to be addressed. The EPA indicated that 0c lack orsampling for SVOC. l AHs and PCBs in subsurface are during the remediatien investigation of the debris burial trenches indicated a data gap because: 1. The EPA Guidance for conducting Remedial Investigations and Feasibility Studies for Landfills indicates that malynes should be taken boom the Target Compound List and Target Acolyte List, which hwede SVOCs and PAI Is.