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Mr Peter MacNicholl <br /> February 21, 2009 <br /> Page 8 <br /> 3. The geologic analysis did not identify a channel that appears to be the main <br /> feature guiding the plume. Understanding of this preferred pathway is needed to <br /> both describe the plume, and to analyze alternatives. <br /> 4. Likewise, the RI invokes organic carbon as an attenuation mechanism but does <br /> not provide supporting evidence. <br /> 5. The RI does not resolve discrepancies between the 'book' behavior of dieldrin <br /> and its actual extent. Many key assertions in the report are not supported by <br /> data from the observed plume. <br /> 6. Key calculations are not validated by field observations. <br /> 7. The RI has not sufficiently supported the proposed preferred alternative. The <br /> preferred alternative is not sufficiently protective of human health and the <br /> environment, particularly in light of the unusual form dieldrin has taken at this <br /> site. <br /> 8. The conceptual model of contaminant transport is inadequate, unsupported by <br /> facts, and does not match observations. <br /> 9. The FS is not acceptable in its current form and should be revised. <br /> Questions regarding this memo should be directed to Ms. Alice Campbell by contacting <br /> her at 818-717-6623 or acampbel(cDdtsc.ca.gov <br />