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Groundwater Well Installation Work Plan Sharpe Army Depot <br /> Lathrop, California <br /> Reviewer Carla Landrum Organization Central Valley Water Board Date April 6, 2023 <br /> Item Reference Review Comment Response <br /> Clarificaiton. Forward tracking partical flow paths have <br /> Appendix A of the Work Plan provides a non-technical been used to illustrate capture of plume boundaries. A <br /> summary of the Work Plan's Extraction Well Evaluation capture zone analysis uses backward tracking particles <br /> and points to the October 2021-September 2022 Federal and would not as effectively illustrate plume capture. <br /> Facility Agreement(FFA)Annual Progress Report(21-22 No revisions have been made. <br /> FFA Report)for more technical detail. 3. Revised. Appendix A has been revised to state the <br /> In general,Appendix A of the Work Plan should: assumption of transient groundwater conditions. <br /> 1. Illustrate the direction of particle flow so the reader can 4. Clarification.The model allows for unconfined <br /> interpret each scenario more clearly(see Figures Al-A5). conditions where the groundwater head may be below <br /> Please also update the color of the particle flow paths for the top of the cell in any given model layer. However, all <br /> easy viewing. particle starting locations shown in the Groundwater <br /> 2. Identify the activity status (i.e., "on" or"off") of existing Well Installation Work Plan are within the fully saurated <br /> nearby extraction wells in Figures Al-A5. If a nearby C Zone, so the particle tracks would not be affected by <br /> extraction well is "on", illustrate its capture radius or zone unsaturated, partially saturated, or unconfined <br /> of influence (see bullet 4 below). conditions.Vertical flow between hydrostratigraphic <br /> 3. Explain if the particle tracking simulations assume a zones did not alter the placement of well screens <br /> steady state or transient groundwater conditions and vertically.The assumption made in the groundwater <br /> why. model is that all new wells are fully screened within the <br /> 4. Discuss how the particle tracking simulations honor the C Zone. <br /> semi-confined aquifer conditions, as described in Section 5. Revised. A baseline scenario for particle tracking is now <br /> 1.2 of the Work Plan, and how vertical flow between shown in Figure Al. <br /> hydrostratigraphic zones influenced the placement of 6. Clarificaion/Revision. Figure 7 has been updated to <br /> proposed extraction wells. reflect the third quarter 2022 hydrogeologic data and all <br /> 5. Include a baseline scenario (i.e., no well installation) so potentiometric surface contours. Proposed new <br /> the reader can understand, and compare,the effects of extraction wells have not been included on Figure 7 as it <br /> extraction well placement relative to this scenario. is meant to illustrate the most current field conditions. <br /> Please understand the 21-22 FFA Report is currently <br /> under agency review. Central Valley Water Board staff will <br /> issue comment on this document within the 60-day FFA <br /> Ahtna Environmental Inc. Page 4 of 6 <br />