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Ramsey (1020035) <br />Public Water Supplier: <br />12/15/2017 <br />Date: <br />Yes, the reference transmissivity value has been changed or added for the following <br />2 <br />aquifers (specify which aquifer and ft/day). Approve and file the amended aquifer test <br />plan. <br /> <br />Step 8 <br /> Was uncertainty adequately addressed in the original WHPA delineation? For example, <br />was variability in aquifer transmissivity and groundwater flowfield addressed explicitly? The <br />latter must include +/- 10% if uniform flow approach was used. <br />The 2007 plan also included an <br /> No changes are needed to address uncertainty. <br />uncertainty analysis that was that was assessed by varying various parameters such <br />as hydraulic conductivity, recharge, and river bed conductance. A series of 11 <br />scenarios were modeled and the final wellhead protection area was obtained by <br />merging the capture zones for all the simulations. The 2017 assessment was <br />performed in the same manner. The results of the capture zone for the 11 scenarios <br />are shown in Figures 1a and 1b for the west and east wellfields, respectively. All <br />captures zones are within the existing DWSMA. The existing DWSMA reflects the <br />computation that would result from the use of a time of travel of 12 years <br />approximately. <br /> <br /> Yes, the WHPA must be amended to address uncertainty. Please specify. <br /> <br />Step 9A10 Years <br /> What was the original ToT? <br /> <br />Step 9B <br /> -- Is there an opportunity to adjust the delineation ToT to maintain the same DWSMA <br />geometry? <br /> No <br />12 years for Wells 1 through 8; <br /> Yes <br /> <br />Step 10 <br /> - Do any of the previous steps indicate the need to redefine the WHPA? <br /> No, proceed to Step 11. <br /> Yes <br />The pumping rates used in the delineation have increased in Well 4 and decreased <br />in Well 8 since the previous delineation. As a result, the predicted capture zone is <br />larger for Well 4 and smaller for Well 8.2 years for Wells 1 through 8. The city of <br />Ramsey indicated that they plan on continuing to pump more water at Well 4 than <br />at Well 8. <br /> <br />In addition, a smaller capture zone is delineated for Wells 1 and 2 using the more <br />recent groundwater model. <br /> <br />Because the previous WHPA was not representative of the existing pumping <br />configuration, a new wellhead protection area is proposed (Figures 2a and b for <br />west and east wellfield, respectively). <br />7 <br />V1.0 2/2013 <br /> <br />