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J�RaosrvFs UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Q A REGION 9 Hawthorne Street San Francisco CA 94105.3901 October 19, 2000 MEMORANDUM SUBJECT: Review of the Baseline Ecological Risk Assessment Solid Waste Management Unit 4 FROM: Clarence A. Callahan, Ph.D., Biologist BTAG Co-coordinator Technical Support Team (SFD-8-B) TO: Michael Work, Remedial Project Manager Army & Pacific Islands Section (SFD -8-3) Summary. Overall this document is an improvement compared to previous versions of the risk assessment. The Army has made significant improvements in presenting the supporting documentation of samples and data collected. EPA suggest that the document would be acceptable if the revisions discussed below are made to this document. EPA suggests that the Army strengthen the risk characterization discussion which is the part of the process that puts the observed level of risk in perspective to the site and other similar sites. See Step 7 [Chapter 7] of the Superfund Risk Assessment Guidance at the following URL: http://www.epa.gov/oerrpa ee /sul2erfund/programs/risk/ecorisk/ecorisk.htm. General comments. PCB congener bioaccumulation -Assuming that PCB congeners bioaccumulate at the same ratio as that found for DDE may contain more uncertainty than is reasonable. The Army should search the literature to find what the PCB bioaccumulation rate is either for total PCBs or for Aroclors as there are probably little if any data available for individual congeners. EPA recommends that the Army review the California Wildlife Exposure Factor and Toxicity Database (hqp://www.oehha.org/cal ecotox/ )that has several citations that evaluate the exposure and toxicity of PCB Arocl6rs on the mallard reproduction. There are only two citations in the ACQUIRE (httn://www.0a.gov/ecotodata base and I believe that these have better coverage in the California data base. For comparison, a bioaccumulation factor derived for McClelland Air Force Base (Data Gap 5 Ecological Risk Assessment Technical memorandum, Magpie Creek and Don Julio Creek, May 2000) Table 4-4. Bioaccumulation Factors, pp24-26 show that for total PCBs the mean value is 25.9 in a 28 day test using Lumbriculus variagatus. This laboratory species is representative of the kinds of organisms that would by found in sediments of Tracy, thus are representative of the food organisms of mallards. Since this is work performed at another Federal Facility and performed by Radian, EPA would suggest that these results are probably representative of bioaccumulation of PCBs in the Tracy pond. These results were derived from laboratory tests 1