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Mr. Maurice Benson March 12, 2009 Page 5 in-situ treatment options for dieldrin are difficult to implement and not.well documented, the screening out of the in-situ technologies was based on literature searches rather than on a benchscale test or pilot study to better determine the applicablility of remediating dieldrin with in-situ technologies. DTSC was surprised by Defense Environmental San Joaquin California (DESJC) lack of interest in investigating alternative in-situ technologies considering their widespread implementation at DDJC-Sharpe for chlorinated compounds in groundwater. DTSC recommends that DESJC more thoroughly investigate the application of In-Situ technologies for dieldrin through benchscale testing prior to eliminating the in-situ treatment from the remedial alternatives. 11. Appendix D, Cost Estimate Details; As mentioned previously in comment #10, the cost estimates presented should also account for offsite permanent compliance monitoring points which would ultimately be located down-gradient on the Alvarez Property including access rights or property acquisition with a land use covenant as part of the land use controls. These components are not accounted for in the cost estimates and should be included to better determine the cost comparison between the alternatives presented. Conclusions: The mass removal test area #2 showed the relative ease at which dieldrin mass can be extracted from the NWC groundwater. Fieldwork analytical results showed the sustained removal of dieldrin mass in both filtered and unfiltered samples, demonstrating the NWC dieldrin's mobility from localized pumping influences such as EW056A. Mass removal test results in combination with DTSC's GSU Theis Analysis demonstrate that the NWC dieldrin mass is more mobile and susceptible to pumping influences than originally conceived, calling into question the accuracy of the perceived (40) extraction wells presented as necessary for dieldrin remediation in the NWC. The mass removal test data and Theis analysis, indicates that a far less number of extraction wells would be necessary to' remediate the dieldrin mass to the Aquifer Cleanup Level of 0.05 pg/L. The effectiveness of the pump and treat remedy for dieldrin in groundwater is already demonstrated at DDJC-Tracy by the reduction of dieldrin concentrations, including lateral extents in the cleanup of the Sanitary Sewage Lagoon dieldrin plume over the last several years.