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' j l serve ARA01e8 Tech U"Wjw-exec nrroeoaor dsub.ur�=.wn oil ow Ary 2916 quantities of VUE , was the sou wordlesse site for VOCs detested in Eastern GSA soil and ground water the results of remedial investigation and baseline risk assessment identified VOCs in ground ias the only contaminants and environmental media of concern in the EaRern GSA. WE dentified as the primary contaminant of concern (COC) in Eastern GSA grouts water, comprising approximately 90% of the teal VOCs detested. Other COCS in ground water included PCE, cis-I,2-dichloroehene (PER), I,I-DCE, chloroform, and bromodichlummemane. The highest coneentertures of VOC contaminants in Eastern GSA ground water were detected in the vicinity of the debris burial trenches. The highest pre-mmediation concentrations of total VOCs and WE detected in shallow ground water near the debris burial trench were approximately 74 micrograms per liter (pits' -) and 71 pg/1., respectively in 1992. Pr'car to the chat of cementation, the plume of"ICE in ground water exceeding the 5 Vg/L MCLextended approximately 4,200 R uRsite. The baseline human health risk assessment for the Eastern GSA estimated airexcess saminogenic risk of 5 x to T for ingesting ground water from a hyputheticallwatersupply well located at the site boundary near the debris but trenches. The risk associated with potential use of contaminated ground water at two existing ofRite water-supply wells (CDFI and SRI) s approximately to 5. These risks were calculated assuming that no remedial actions were taken and the VOCs in Eastern GSA ground water migrated to these wells. The bowline human health risk assessment indicated that there was no un expmble risk or hazard associated with potential exposure to VOCS in surface or whourf soil in the Eastman GSA, and n contaminants of concern were identified in thew media. There is no surface water prevent be the Reiman GSA. The historic mandruturn WE co unsaturated soilhock in the Eastern GSA RIM4 mg/kg) is also below both then residential and industrial wll Min (June 2015) that incorporate the rown0y revised WE toxicity value. The EPA residential soil RSLs (June 2015) for ME are 0.Mmp/kg (cancer risk) and TI mg/kg (non-cancer elites); the industrial soil RSU (June 2015) foe WE are 6.0 mg/kg (anca risk) and 19 mg(kg (noncaacer eRects). The SWRT risk assessment determined that VOCs and metals in mil, including samples collated from the debris burial trenches/area, did not pose an unacceptable risk or haard to human or ecological receptors, or a become threat to ground water. As a result, VOCs and metals were not designated as contaminants ofconcerm in surface or subsuef soil in the Eastern GSA. 'therefore, capping of or other remedial measures for the debris burial trenches ere not deemed eceswa by DOE, the U.S. EPA, the California DISC, and the RWQCB, and it was not included as alternative in the GSA Feasibility Study or as a component of the selected remedy in the GSA ROIL. The fact that there was no rebound of VOCs in ground water above the MCI. cleanup standard in over five years of monitoring following treatment system shutdown, and that VOC continued to decrease towards reporting limits during this time, provides further evidence that the debris burial trenches are not a Significant continued source of VOCs to Eastern GSA ground water. No unacceptable risk or haeord was identified for ecological receptors in the baseline risk