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ATTACHMENT II <br /> EPA COMMENTS ON THE DRAFT FINAL <br /> COMPREHENSIVE RI/FS WORK PLAN (MAY-92) <br /> DEFENSE DISTRIBUTION REGION WEST-TRACY <br /> BASELINE RISK ASSESSMENT <br /> NOTE: The baseline risk assessment portion of the work plan has <br /> undergone extensive revision. It is largely a new submittal. <br /> Due to the deficient previous draft and the limited time to <br /> incorporate EPA' s comments in this draft final (one review cycle) <br /> EPA expects all our following comments to be addressed in the <br /> text of the revised BRA portion of the Comprehensive RI/FS Work <br /> Plan. The comment numbers below do not correspond to the <br /> previous EPA comments of March 6, 1992 . <br /> GENERAL COMMENTS <br /> 1. If the Defense Distribution Region West-Tracy (DDRW-Tracy) <br /> wants to use the results of the Phase I RI to deselect sites <br /> from further study, then the current BRA Work Plan (May <br /> 1992) is not acceptable. Specifically lacking are <br /> preliminary remediation goals (PRGs) and detailed <br /> information regarding how the analytical detection limits <br /> were evaluated to determine if they are adequate for risk <br /> assessment purposes. An important use of PRGs is to <br /> evaluate the adequacy of analytical detection limits used to <br /> provide data for risk assessment: method <br /> detection/quantitation limits can be compared to risk-based <br /> concentrations (PRGs) . Also, as Phase I data becomes <br /> available, actual contaminants in site media can be compared <br /> to PRGs, to identify contaminants of concern for sampling in <br /> subsequent phases of field work and perhaps deselect <br /> contaminants from further investigation. <br /> Suggested steps involved in the development of PRGs are: <br /> identify potential chemicals of concern; identify potential , <br /> applicable, or relevant and appropriate requirements (ARARs) <br /> for air, water, and soil ; assemble toxicity information; <br /> calculate risk at ARARs ; and calculate risk-based <br /> concentrations. A list of chemicals of potential concern <br /> can be developed from information about site use history and <br /> sampling efforts prior to the RI . Chemicals can be added to <br /> or deleted from the list as more information becomes <br /> available during the RI . Chemical-specific standards for <br /> air, water, and soil , as specified in federal or California <br /> regulations that may become ARA-Rs can be identified for each <br /> expected contaminant (Maximum Contaminant Levels or MCLS for <br /> water) . Toxicity values for human health risks will be <br /> II-1 <br />