WORK PLANS - Laserfiche WebLink

Home Browse Search

and an overflow pond cam of the sewage pond. Debris burial trenches, Wal were used to dispose of craft shop debris in the I WAs and early 1970s, are located immediately north or the overflow, pond. Other structures Present in the pastern GSA include former ground water extraction and coo wells and a ground water treatment system that were used to extract, monitor, and treat contaminated coed ground water prior to the achievement of cleanup standards in 2007. There are also several dim rinds N the area ram were mnsnucmd 10 averts the sewage and overflow pond, and treatment facility and extraction wellfield. The current bond use in the Fxstern GSA is industrial. The Eastern GSA, as well as mom of Site 300, has also been designated as critical habitat for protected wildlife resources. ORsie property adjacent to the Easton GSA includes Privately owned rangeland and a residence to the south, and an ecological preserve owned by the California Department of fish and Wildlife. Evidence of a chemical refuse to ground water in the GSA was f t discovered to 19H2 when tricblomnthylene ('IVE) was noticed in Wei] 7, a former onsite Site 300 water-supply well located in the Central GSA. Further investigations led to the discovery and investigation of real other release areas in the GSA, including the debris burial trenches in the Eastern GSA. In ti the 1960s and Vyift volatile organic compound (VOC)-contaminated debris was buried in riches located in the Fasters GSA causing VOC contamination orground water and subsurface sail (figure 3). In 1991, ground water extraction and treatment began in the pastern GSA as a ma-mre- critical signed H Depen l I In wilitynAgreement IDEA)EPA, furr the clea California up of I.LNICSite and 300. The Sit, DOE Wide Remedial Investigation report was issued in Pool, billowed by the Feasibility Study for the GSA OU and Proposed Plan fur Environmental Cleanup ofthe GSA OU. An OU specific ROD fur the GSA OU was signed in January 19W. The Remedial Design for the GSA OU was issued is 1998. Remedial action construction completion coos documented in June 2005. EPA performed a construction completion inspection on July 13, 2005. Five Year Reviews were completed in 2001 (Ferry cl a1„ 2001b 2006 (Dibley ct al., 2006). and 2011 (Valmt m al., 2011). RemMietion eflhrls in the pas m GSA successfully reduced concentrations of VGCs in ground water to below the cleanup standards set in the GSA ROD, and the Cast" GSA ground water extraction and treatment system was shut off on February 15, 2007 with regulatory approval. As required by the GSA ROD, ground water monitoring was conducted for five years after shutdown to determine if VOf: commanmtions would rise or "rebound' above cleanup standards. The results of the monitoring, which confirmed that VOC concentrations had remained below cleanup standards in the five-year post shutdown monitoring period, were Prevented at the February U, 2012 RPM Meeting. The regulatory agencies agreed fat cleating Of the Eastern GSA was complete, monitoring and reporting could cease, and that close out documentation should Issmanihed Draft and Dmfl Final Close Out Reports, documenting [teal remediation of the Eastern GSA Portion of the GSA OU had been completed, were submitted to the regulatory agencies in December 2012 and June 2013, respectively. As discussed in Section 1 .1, following submittal of the Utah Final Close Out Report in June 2013, EPA and the R WQCR requested and DOE agreed to collect additional subsurface soil samples fora the Entries GSA debris burial much area for SVOSYPAI I and FUR analysis 0 detention if these constituents are present, and if present,