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Mr. Maurice Benson March 12, 2009 . Page 3 transport "host" if any, and whether the dieldrin is truly bound to organic carbon, silica particles, quartz, montmorillonite, etc. DTSC recommends that the Contaminant Properties section should be revised acknowledging the results from the dieldrin mass removal tests, especially at EW056A, showing that dieldrin mass in the northwest corner is more mobile and sustainable to groundwater extraction than originally perceived. 4. Appendix B, Page 4-2, Section 4.0, Conclusions #6; The Section states "There is no evidence in the data to indicate dieldrin greater than 0.45 pm in size can be removed from the aquifer over distances greater than 6 feet from the pumping well. And although EW056A discharge samples show dieldrin greater than 0.45 pm in size was removed during the test, these data suggest the removal of this greater than 0.45 Nm size fraction is unsustainable." This statement contradicts the 3rd bullet on page 3-13 (Dieldrin Results) stating "By contrast, dieldrin concentrations greater than 0.45 Nm in size do not consistently increase or decrease throughout the pumping period in pumping well EW056A or in any of the performance monitoring wells. Instead, dieldrin concentrations greater than 0.45 Nm in size in these wells are relatively stable compared to that for dieldrin less than 0.45 Nm in size." DTSC recommends the conclusion section be revised to account for the contradiction on the sustainability of pumping of dieldrin mass greater than 0.45 um for consistency and conciseness. 5. Appendix B, Table 3-3, Dieldrin Concentration in Wells; Plotting the EW056A dieldrin concentrations in the influent, including filtered and unfiltered samples from performance monitoring wells (LM190A, LM191A, LM141AU) in most cases, showed steady if not increasing dieldrin concentration trends in groundwater samples as the mass removal tests preceded the 30-day duration until shutdown. Groundwater analytical data from the EW056A extraction area show that dieldrin mass smaller than the 0.45 um can be easily mobilized from the saturated soil matrix and appears sustainable with increasing trends at the end of the test as a result of a minimal pumping influence of approximately 10 gpm (See provided figures). 6. Appendix B, Figure 2-2; According to the figure's legend, the distances from EW056A to the performance monitoring wells might be a couple feet farther apart than the 12 feet distance stated in the report and should acknowledge this discrepancy in both the text and figures because no official surveying coordinates are provided for verification or documentation of distances.