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Map ID MAP FINDINGS
<br /> Direction
<br /> Distance EDR ID Number
<br /> Elevation Site Database(s) EPA ID Number
<br /> TRACY DEFENSE DEPOT(USARMY) (Continued) 1000182407
<br /> study(RI/FS)was conducted to address the groundwater plume. In 1991,
<br /> DDJC-Tracy was listed as a Superfund Site on the National Priorities List
<br /> (NPL).On June 27,1991,DDJC-Tracy,the U.S.EPA Region 9,and the California
<br /> Department of Toxic Substances Control(DTSC)signed a Federal Facilities
<br /> Agreement(FFA)for DDJC-Tracy.This FFA has enforceable schedules;it ensures
<br /> that environmental impacts are thoroughly investigated and that appropriate
<br /> cleanup actions are taken to protect human health,welfare,and the
<br /> environment.Consistent with the requirements of the FFA,the U.S.EPA,DTSC,
<br /> and the California Regional Water Quality Control Board(RWQCB)provide
<br /> regulatory oversight,including technical support,review,and comment on all
<br /> investigative and cleanup work at DDJC-Tracy. The following sites were
<br /> identified as potential threats to human health and the environment:36 SWMUs;
<br /> 10 drum storage areas with soil contamination;28 Underground storage tanks
<br /> (USTs);contaminated groundwater associated with Operable Unit 1 (OU1);the Day
<br /> Care Center;and other areas with surface and near-surface soil
<br /> contamination. Operable Unit 1 There are a number of Solid Waste Management
<br /> Units(SWMUs)and areas within OU1.Each of these SWMUs has a separate selected
<br /> remedy.Descriptions of the SWMUs follow the history of OU1. Following the
<br /> signing of the FFA,contaminated groundwater was identified as the"principal
<br /> threat"at the depot,and actions to address contaminated groundwater were
<br /> given priority. A baseline risk assessment and the feasibility study(FS)
<br /> for OU1 were completed in 1992. In August 1993,a Record of Decision(ROD)was
<br /> issued for remediation of volatile organic compounds(VOCs)in groundwater.
<br /> The effluent treatment standards for several VOCs and pesticides not included
<br /> in the OU1 ROD were adopted into the OU1 ROD through an Explanation of
<br /> Significant Differences(ESD). The OUt ESD also modified the technology for
<br /> removing VOCs from the aquifer to include dispersion. At the same time,a
<br /> remedial investigation/feasibility study(RI/FS)was initiated to more
<br /> thoroughly evaluate the contamination associated with OU 1 and to address the
<br /> areas of soil contamination that were not addressed as part of the OU 1 ROD.
<br /> The RI/FS report includes an evaluation of possible remedies for the sites
<br /> identified as posing a threat to human health or the environment.A proposed
<br /> plan was then prepared for public review.The purpose of the proposed plan was
<br /> to describe recommended remedies,provide information to the public about the
<br /> actions planned at the sites,and encourage public input prior to making a
<br /> final decision on a remedy. In April 1998,the Final Site-Wide Comprehensive
<br /> Record of Decision(ROD)for DDJC-Tracy was signed.The ROD included and
<br /> evaluation of all groundwater issues and addressed all sites with soil
<br /> contamination. A ROD Amendment addressing site-wide groundwater,SWMU 4,
<br /> and DSERTS 72 was completed in June 2001. An Explanation of Significant
<br /> Differences(ESD)describing changes to the selected remedies for Solid Waste
<br /> Management Units(SWMUs)2,3,and 4 and the Northern Depot Soils Area was
<br /> signed July 31,2001.The lead agency for this ESD is the Defense Logistics
<br /> Agency(DLA). The 2001 ESD addresses 4 of these SWMUs and 2 areas:SWMU 4,
<br /> SWMU 2 and 3,Northern Depot Soils Area,SWMU 7,Building 30 Drum Storage Area,
<br /> and SWMU 33. An Explanation of Significant Differences addressing SWMUs 1,
<br /> 2,3,4,6,7,8,20,24,and 33,DSERTS 67(Northern Depot Soils Area)and 72,
<br /> Building 30 Drum Storage Area,Eastern Depot Soils Area,and Southern Depot
<br /> Soils area of OU 1 was completed September 27,2004- Site-Wide
<br /> Groundwater The groundwater at DDJC-Tracy has been affected by various
<br /> contaminants,including chlorinated hydrocarbons and pesticides.The
<br /> contaminated groundwater is present in a plume that is migrating off site to
<br /> the northeast.This plume of contamination is identified primarily by
<br /> concentrations of tetrachloroethene(PCE)and trichloroethene(TCE). The
<br /> remedy selected in the ROD for OU 1 groundwater includes extraction wells,air
<br /> stripping to remove volatile organic compounds(VOCs),carbon treatment to
<br /> remove dieldrin,and reinjection into injection galleries.The ROD specified
<br /> TC3372962.1s Page 37
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