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Department of Toxic Substances Control <br /> Maureen F. Gorsen, Director <br /> Linda S.Adams 8800 Cal Center Drive <br /> Sacramento, California 95826-3200 Arnold Schwarzenegger <br /> Agency Secretary <br /> Cal/EPA Governor <br /> REC F§WED <br /> October 5, 2007 <br /> OCT Y 0 2001 <br /> ENVIRONMENT <br /> PERM1TISERV SES TH <br /> Mr. Marshall Cloud <br /> Defense Logistics Agency <br /> Defense Distribution Depot San Joaquin, Tracy Site <br /> Post Office Box 960001 <br /> Stockton, California 95296-0250 <br /> RESPONSE TO TECHNICAL IMPRACTICABILITY EVALUATION FOR OPERABLE <br /> UNIT 1 DIELDRIN REMEDY & REQUEST FOR AGENCY INPUT DATED <br /> AUGUST 22, 2007, FOR DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN <br /> CALIFORNIA (DDJC), TRACY SITE, TRACY, CALIFORNIA <br /> Dear Mr. Cloud: <br /> The Department of Toxic Substances Control (DTSC) received the above-mentioned <br /> letter on August 29, 2007. The letter briefly discusses some of the talking points made <br /> during previous dieldrin-specific meetings and teleconferences attended by all the <br /> agencies' Project Managers. Additionally, the letter requests the regulatory agencies' <br /> input on guidance to be used for preparing a Technical and Economic Feasibility <br /> Analysis (TEFA) for dieldrin in ground water, and a brief explanation of their position on <br /> raising the Aquifer Cleanup Level (ACL) for dieldrin at DDJC-Tracy. <br /> In preparing the TEFA for dieldrin, DTSC recommends using the 1993 United States <br /> Environmental Protection Agency's (USEPA's) "Guidance for Evaluating the Technical <br /> Impracticability of Groundwater Restoration." If newer guidance is available by the <br /> USEPA, DTSC recommends using the newest guidance. <br /> DDJC-Tracy's ACL of 0.05 micrograms per litre (Ng/L) for dieldrin appears to equate to <br /> a 2.5 E-5 cancer risk for a 30-year exposure. DTSC's point of departure for decision is <br /> 10-6 risk for a 30-year exposure. DTSC understands that the USEPA can make a risk <br /> management decision within a range of 10-4 to 10"6. <br /> Since no primary Maximum Contaminant Level exists for dieldrin, Comprehensive <br /> Environmental Response, Compensation, and Liability Act defaults to a risk evaluation <br /> for a cleanup goal. <br />