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Corrective Action: Explain in the ROD that the decision to set cleanup standards nor <br /> other volatiles (e.g., carbon tetrachloride and chloroform) for inorganics (e.g., a <br /> and chromium) and pesticides (e.g., dieldrin) has been deferred.' Include a listing <br /> of all 17 of the chemicals of concern identified in the risk assessment for OU #1 and <br /> include text for each which explains why a cleanup standard is established in this <br /> ROD, why a cleanup standard is not necessary, or why the decision to set a cleanup <br /> standard is being deferred to the Comprehensive RI/FS. Possible reasons for <br /> deferring the decision to set a cleanup standard are: lack of conclusive data to <br /> identify source of contamination, unresolved issues regarding quality of database. <br /> These rationale and others need to be stated in this ROD so that the decision process <br /> will be apparent to the reader of the FS and the ROD. <br /> Corrective Action: Include DCE as contaminant to be addressed by this ROD. <br /> 5. Declaration, Description of the Remedy <br /> The first sentence of the second paragraph needs to reflect how the selected remedy <br /> will dispose of the treated groundwater. <br /> Revise this sentence to state ". . . and disposal of the treated water by returning it to <br /> the aquifer from which it has been xtr t " <br /> 6. Declaration, Description of the Remedy <br /> The first sentence of the second paragraph needs to be revised to reflect that (a) only <br /> one additional stripper is to be constructed (as opposed to "one or more additional <br /> similar air stripping systems"), and (b) additional extraction and injection wells will <br /> be installed (that the remedy will need more than those already in place). <br /> Corrective Action: Revise this sentence to state " . . . using the current IRM air <br /> stripping system plus one additional air stripping system." <br /> 7, Declaration, Description of the Remedy <br /> The second sentence in the second paragraph should be revised to reflect the fact <br /> that the surface impoundments are also to be used to return the treated groundwater <br /> 1 The FS for OU #1 indicated that other volatiles, pesticides, and inorganics (e.g., <br /> chloroform, carbon tetrachloride, dieldrin, chromium, arsenic) may be present at levels <br /> which pose significant health risks. Due to uncertainties regarding the source of these <br /> contaminants or questions regarding the turbidity of groundwater samples, it was agreed <br /> that these other contaminants would be further <br /> tevaluate <br /> propose cleanup levels for in the Comprehensive <br /> RI. A <br /> decision on whether DDRW-Tracy <br /> would need contaminants would be documented in the Comprehensive ROD. The groundwater plume is <br /> still most accurately described as containing these contaminants (albeit in lesser volumes), <br /> which pose risks. <br /> 2/40 <br /> EPA/R9 June 7, 1993 <br />