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• (�It��iA\ • <br /> Department of ToxicSubstances Control µa: <br /> Arnold <br /> rima S.MargsSchw=enegger <br /> Secro for MaureenI.Crorsen,'Uirecior <br /> Environnv nal Protection 9211 Oakdale Avenue Governor' <br /> Chatsiwrai,.CA 91311 <br /> MEMORANDUM <br /> TO: Peter MacNicholl <br /> 8800 Cal Center Drive <br /> Sacramento, CA 95826 <br /> FROM: Riz A. Sarmiento, Ph.D. <br /> Staff Toxicologist <br /> Human & Ecological Risk Division (HERD) <br /> DATE: February 4,2009 <br /> SUBJECT: DRAFT NORTHWESTERN CORNER DIELDRIN PLUME FEASIBILITY <br /> STUDY REPORT,DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN, <br /> TRACY SITE <br /> Document Reviewed: The Human and Ecological Risk Division (HERD) reviewed the <br /> above-referenced report prepared by URS and dated November 2008, <br /> Scope of Review: HERD's review focused on the portions of the report relevant to the <br /> baseline human health risk assessment. <br /> Background: Investigations were conducted from 1995 to 2007 to delineate the lateral and <br /> vertical extent of dieldrin in groundwater. Maximum detected historical concentration of dieldrin <br /> is reportedly 0;26 micrograms per liter (uglL) detected in 2006. Two investigations were <br /> conducted in 2008 to provide information that could support the selection of remedial <br /> alternatives. Although groundwater at the Site is not being used for domestic or worker use, the <br /> human health risk assessment assumes that.that groundwater is being hypothetically used for <br /> domestic and industrial purposes. <br /> SPECIFIC COMMENTS <br /> 1. Section 5.1.2,Receptor Characteristics, page 5-2 <br /> It is incorrect to identify potential receptors as EPA Resident receptor and DTSC Resident <br /> receptor: There is no difference between the assumed exposure conditions recommended by <br /> EPA and DTSC. The age-adjusted factor recommended by EPA incorporates the different <br /> ingestion rates, exposure durations, and body weights of the adult and child residents that are <br /> 0 Printed on Recycled Paper <br />