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1 / <br /> Mr. Marshall Cloud <br /> December 13, 2006 <br /> Page 2 <br /> flow model, while the September and November meetings verified model calibration and <br /> the fate and transport of site contaminants, respectively. <br /> DDJC intends on developing a Draft 3-Dimension Ground Water Model Report for <br /> DDJC-Tracy documenting the development, calibration, parameters, and predictive <br /> results to support optimization efforts in groundwater pump and treat system at <br /> DDJC-Tracy. <br /> DTSC has reviewed the modeling handouts and has the following comments: <br /> Comments <br /> 1 . DTSC recommends analyzing boron trends from groundwater analytical data as <br /> an independent check for the recharge estimates due to the uncertainty with the <br /> recharge values. <br /> 2. The 3-D Model shows that Total Organic Carbon (TOC) is a very sensitive <br /> parameter in relation to the fate and transport of site contaminants. Presently, <br /> DDJC-Tracy has very little TOC data to support model predictions, contributing <br /> significantly to the overall model uncertainty in predicting contaminant <br /> distributions. DTSC recommends future Cone Penetrometer Testing sampling <br /> efforts at DDJC-Tracy to collect site specific TOC data to input into the 3-D Model <br /> for future model runs. <br /> 3. DTSC recommends verifying that the 3-D Model is only using1996 and newer <br /> data in order to help determine the mechanism(s) responsible for the "ghost' <br /> plumes in the TCE, PCE and Dieldrin models. <br /> 4. As requested during the September 28, 2006 modeling meeting, DTSC <br /> recommends including particle tracking maps for TCE, PCE and Dieldrin in the <br /> Draft 3-D Model Report. <br /> 5. The 2005 simulated versus observed concentrations for PCE data shows a bad <br /> data fit with many of the simulated points more than three standard deviations <br /> from observed. The bad data fit suggests that mechanisms not accounted for in <br /> the 3-D Model may be occurring beneath DDJC-Tracy. <br />