Agenda - Council - 10/08/2019 - Laserfiche WebLink

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Public Water Supplier: Ramsey (1020035) Date: 12/15/2017 ❑ Yes, the reference transmissivity value has been changed or added for the following aquifers (specify which aquifer and ft2/day). Approve and file the amended aquifer test plan. Step 8 — Was uncertainty adequately addressed in the original WHPA delineation? For example, was variability in aquifer transmissivity and groundwater flowfield addressed explicitly? The latter must include +/- 10% if uniform flow approach was used. • No changes are needed to address uncertainty. The 2007 plan also included an uncertainty analysis that was that was assessed by varying various parameters such as hydraulic conductivity, recharge, and river bed conductance. A series of 11 scenarios were modeled and the final wellhead protection area was obtained by merging the capture zones for all the simulations. The 2017 assessment was performed in the same manner. The results of the capture zone for the 11 scenarios are shown in Figures la and lb for the west and east wellfields, respectively. All captures zones are within the existing DWSMA. The existing DWSMA reflects the computation that would result from the use of a time of travel of 12 years approximately. ❑ Yes, the WHPA must be amended to address uncertainty. Please specify. Step 9A — What was the original ToT? 10 Years Step 9B -- Is there an opportunity to adjust the delineation ToT to maintain the same DWSMA geometry? ❑ No • Yes 12 years for Wells 1 through 8; Step 10 - Do any of the previous steps indicate the need to redefine the WHPA? ❑ No, proceed to Step 11. • Yes The pumping rates used in the delineation have increased in Well 4 and decreased in Well 8 since the previous delineation. As a result, the predicted capture zone is larger for Well 4 and smaller for Well 8.2 years for Wells 1 through 8. The city of Ramsey indicated that they plan on continuing to pump more water at Well 4 than at Well 8. In addition, a smaller capture zone is delineated for Wells 1 and 2 using the more recent groundwater model. Because the previous WHPA was not representative of the existing pumping configuration, a new wellhead protection area is proposed (Figures 2a and b for west and east wellfield, respectively). V1.0 2/2013