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Map ID MAP FINDINGS Direction Distance Distance(ft.) EDR ID Number Elevation Site Database(s) EPA ID Number USDOD DVF DIST REGION WEST TRACY (Continued) 1000182407 depot. The storm water pond receives runoff from the depot's storm drain system. The sewage I agoons receive treated wastewater from the depot's wastewater treatment plant. The only landscaped area is in the northwest comer near Building 100. All other unpaved surfaces contain weeds and grass,which historically have been removed regularly with herbicides(types and quantities were not recorded) and/or by grading. In early 1980,a records search by the U.S.Army Toxic and Hazardous Materials Agency(USATHAMA)first identified 25 waste sites,known as solid waste management units(SWM Us)1 through 23,2A,and 10A,at Defense Distribution Depot San Joaquin (DDJC)-Tracy that contained contaminants that could migrate to off-depot locations. Because of the potential for contaminants to migrate to groundwater, 12 monitoring wells were installed in July 1980 and sampled for metals and general water quality parameters. In May 1984,the Central Valley Regional Water quality Control Board(RWQCB)was advised that trichloroethene(TCE) wand tetrachloroethene(PCE)concentrations in three monitoring wells exceeded the California Department of Health Services(DHS)action level of 5 micrograms per liter(ug/I). Ultimately,a remedial investigationtfeasibility study(RI/FS)was conducted to address the groundwater plume. I n 1991,DDJC-Tracy was listed on the National Priorities List(NPL). In June 1991,DDJC-Tracy,the U.S. Environmental Protection Agency(EPA)Region IX,and the Califomia Department of Toxic Substances Control(DTSC)signed a Federal Facilities Agr eement(FFA)for DDJC-Tracy. The following sites were identified as potential threats to human health and the environment: 36 SWMUs; 10 drum storage areas with soil contamination;28 Underground storage tanks(USTs);contaminated groundwater associa ted with Operable Unit 1 (OU1);the Day Care Center;and other areas with surface and near-surface soil contamination. A baseline risk assessment and the feasibility study(FS)for OU1 were completed in 1992. In August 1993,a Record of Decision(R OD)was issued for remediation of volatile organic compounds(VOCs)in groundwater. The effluent treatment standards for several VOCs and pesticides not included in the OU1 ROD were adopted into the OU1 ROD through an Explanation of Significant Differences(ESD). The OU1 ESD also modified the technology for removing VOCs from the aquifer to include dispersion. A site-wide comprehensive ROD was issued in April 1998 that included and evaluation of all groundwater issues and addressed all sites with soil contamination. CERCLIS Assessment History: Assessment: DISCOVERY Completed: 08/01/1980 Assessment: PRELIMINARY ASSESSMENT Completed: 10/01/1986 Assessment: PROPOSAL TO NPL Completed: 07/14/1989 Assessment: HRS PACKAGE Completed: 08/30/1990 Assessment: FINAL LISTING ON NPL Completed: 08/30/1990 Assessment: SITE INSPECTION Completed: 09/06/1990 Assessment: FEDERAL INTERAGENCY AGREEMENT Completed: 06/27/1991 Assessment: AG NEGOTIATIONS Completed: 06/27/1991 Assessment: RECORD OF DECISION Completed: 08/12/1993 Assessment: FF RI/FS Completed: 08/12/1993 Assessment: FF RD Completed: 02/26/1996 Assessment: RECORD OF DECISION Completed: 04/14/1998 Assessment: FF RI/FS Completed: 04/14/1998 Assessment: FF REMOVAL Completed: 07/13/1998 Assessment: FF RD Completed: 09/23/1999 TC931160.3s Page 8