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1 STATE OF CALIFORNIA • • <br /> PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— <br /> CENTRAL VALLEY REGION '- <br /> 3443.R0 UTIER ROAD. SUITE A <br /> SACRAMENTO, CA 95827-3098 {5 •' <br /> PHONE: (916) 361-5600 RE Y _ Gk^ i <br /> FAX: (9'•61361-5686 V <br /> OCT 0 7 1992 <br /> 5 October 1992 ENVIRONMENTAL HEALTH <br /> PERMITISERVICES <br /> Mr. Michael Work <br /> Federal Facilities Enforcement Branch <br /> Office of Superfund (H-9-1) <br /> Environmental Protection Agency, Region IX <br /> 75 Hawthorne Street <br /> San Francisco, CA 94105-3901 <br /> POTENTIAL PESTICIDE PLUME, DEFENSE DISTRIBUTION REGION WEST (DDRW), TRACY, SAN <br /> JOAQUIN COUNTY <br /> We have reviewed your 26 August 1992 letter on the Draft Engineering Report for <br /> Well Evaluation and Abandonment for DDRW, Tracy. Your letter states that the <br /> presence of Dieldrin, DDD and DDE in the ground water samples from below 515 <br /> feet in Well No. 1 could indicate that a pesticide plume exists within the Lower <br /> Tulare Formation. You also state that DDRW, Tracy must address this possible <br /> contamination in the Comprehensive Remedial Investigation/Feasibility Study <br /> (RI/FS) . <br /> These statements cause us considerable concern for two reasons. First, we <br /> believe that it is premature to imply that a pesticide plume in the Lower Tulare <br /> has resulted from waste disposal practices at DDRW, Tracy. We also believe that <br /> there are insufficient technical data on which to base your position and have <br /> listed below the reasons why we cannot support the Environmental Protection <br /> Agency's (EPA) position on this issue. <br /> 1 . Ground water samples from the monitor wells surrounding Well No. 1 (LM-24, <br /> LM-25, LM-61 and LM-85) , which are screened in the Upper Tulare, have not <br /> had detectable concentrations of Dieldrin, DDD or DDE. The lack of <br /> pesticides in the Upper Tulare near Well No. 1 indicates that this well may <br /> not have contributed to the downward vertical migration of these <br /> contaminants. <br /> 2. The concentrations of Dieldrin, DDD and DDE in all of the ground water <br /> samples from Well No. 1 were less than 1 microgram per liter (µg/l ) . DDD <br /> and DDE are associated pesticides and are breakdown products of DDT which <br /> was banned in 1973. DBCP is another persistent pesticide and its use was <br /> suspended in 1979. Low concentrations of DBCP are known to occur in ground <br /> water and can be verified through the Department of Pesticide Regulation. <br /> Therefore, low concentrations of other persistent pesticides may occur in <br /> ground water on a regional basis in agricultural areas. Furthermore, low <br /> concentrations of pesticides in ground water does not necessarily indicate <br /> the presence of a point-source contaminant plume. <br />