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February 23,2023 <br /> Page 3 <br /> In this scenario, proposed EWCC7 was also moved closer to the offsite plume in the Central <br /> Area on the railroad right-of-way from its prior location farther downgradient of that <br /> plume and on site. This new location is closer to the core areas of the offsite plume. The <br /> shorter particle pathways from the plume to EWCC7 in this location indicate more efficient <br /> mass removal and plume containment as compared to prior scenarios. <br /> Scenario 4 <br /> Figure A5 shows the results of revised extraction well configuration Scenario 4. In this <br /> scenario, proposed EWCC7 was moved farther south, closer to the offsite Central Area <br /> plume, and onto the railroad right-of-way. The well would provide efficient capture and <br /> mass removal in this location,but appears less effective than the Scenario 3 location as it <br /> would not help to address the incomplete or inefficient capture of the northernmost plume <br /> west of the Sharpe facility boundary. <br /> Scenario 5 <br /> Figure A6 shows the results of revised extraction well configuration Scenario 5. The only <br /> change in this scenario is that proposed EWC9 was moved closer to the Site,but still on the <br /> railroad right-of-way. EWC9 would provide efficient capture and mass removal in this <br /> location. <br /> Conclusions <br /> Based on the particle tracking results of various pumping configuration scenarios <br /> presented herein, it is anticipated that the preferred configuration of proposed new wells <br /> will be a combination of the Scenario 3 and Scenario 5,with proposed EWC9 on the <br /> railroad right-of-way as shown in Scenario 5, and proposed EWCC7 on the railroad right- <br /> of-way as shown in Scenario 3. These recommended locations are expected to mitigate the <br /> inefficient capture of the offsite COC plumes in the South Balloon and Central Area. This <br /> improved capture would likely also be associated with improved contaminant mass <br /> removal and associated improvements in cleanup time. <br /> The results of this capture zone analysis are subject to the same assumptions and <br /> limitations documented in the model update appendix presented in the FFA Annual <br /> Progress Report. <br /> Please let me know if you have any questions. <br /> Sincerely, <br /> inte Cd! <br /> 04Ano <br />