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ao sq, <br /> s r UNITED STATES ENVIRONMENTAL PROTECTION AGENCY <br /> 0 <br /> '3F REGION IX <br /> ( 11`k PRO11 V 75 Hawthorne Street' <br /> San Francisco, CA 94105-3901y ! hD <br /> MAR 2 3 1993 <br /> March 17, 1993 ENVIRONMENTAL HEALTH <br /> PERMIT/SERVICES <br /> Marshall Cloud <br /> Env. Protection Office, DDRW-Tracy <br /> P.O. Box 960001 <br /> Stockton, CA 95296-0250 <br /> RE: Contour Maps Dieldrin and Arsenic <br /> Dear Marshall, <br /> SAIC has prepared the attached contour maps, based on JMM's September 1992 <br /> quarterly monitoring round at DDRW-Tracy, for discussion at the meetings of March 30-31, <br /> 1993. <br /> On each contour, the cancer risks represented by concentrations of each carcinogen <br /> (assuming a residential drinking water scenario) are labeled. Arsenic and dieldrin are both <br /> relatively mobile in the subsurface compared to other metals and organochlorine pesticides, <br /> such as DDT. Based on present knowledge, arsenic and dieldrin appear to be the major <br /> contributors to the carcinogenic risk for groundwater at the IWPs (SWMU No. 3) and <br /> possibly at part of the IWPL. It should be noted that the September 1992 monitoring round <br /> by JMM was the first to obtain nonturbid total metals data. <br /> Please contact me at (415) 744-2392, should you have any questions. <br /> Sincerely, <br /> 'w4't'-d W'-" <br /> Michael Work <br /> Remedial Project Manager (H-9-1) <br /> Office of Superfund <br /> Attachment <br /> cc: (See Attached List) <br /> Printed on Recycled Paper <br />