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Department of Toxic.Substances Control <br /> Linda S.Adams <br /> Arnold <br /> Secretary for Schwarzenegger <br /> Environmental Protection Maureen F. Gorsen,Director Governor <br /> 8800 Cal Center Drive <br /> Sacramento, California 95826-3200 <br /> MEMORANDUM <br /> TO: Peter MacNicholl <br /> Office of Military Facilities <br /> 8800 Cal Center Drive <br /> Sacramento, CA in 95826-3200 <br /> FROM: John P. Christopher, Ph.D., D.A.B.T. <br /> Staff Toxicologist <br /> Human & Ecological Risk Division(HERD <br /> JChristo ,dtsc.ca.eov 916.255.6630 <br /> DATE: 11 April 2007 <br /> SUBJECT: Defense Depot Tracy: Assessment of Dieldrin in Groundwater <br /> PCA: 14740 Site: 100048-47 <br /> BACKGROUND <br /> Defense Distribution Depot San Joaquin Tracy Site is a military facility in San Joaquin County. <br /> Prior investigations identified dieldrin in groundwater. The current document is an assessment of <br /> risk and hazard due to this environmentally persistent chlorinated insecticide. <br /> DOCUMENT REVIEWED <br /> We reviewed a letter report entitled, "Defense Distribution Depot San Joaquin Tracy Site, Hy- <br /> pothetical Risk& Hazard Exposure Scenario for Dieldrin". This document is dated 1 March 2007. <br /> It was prepared by the Defense Logistics Agency. The letter report contained an e-mail, analyti- <br /> cal data on dieldrin in groundwater, and several tables summarizing calculations of risk for a <br /> residential exposure to groundwater used for domestic purposes. <br /> COMMENTS <br /> 1. Overall: The assessment by the Department of Defense is incomplete, because no assess- <br /> ment is presented for the highest concentration of dieldrin (CmAx), as required by prior <br /> agreement. An assessment using Cm,,;Ly would have resulted in estimated cancer risk and non- <br /> cancer hazard in excess of the "risk management ranges. Therefore, dieldrin should be re- <br /> tained as a chemical of concern in groundwater. We re-analyzed the data set for the Depart- <br /> ment of Defense, eliminating duplicates results and confirmation samples, and calculating an <br /> Printed on RervrlPrl Paner <br />