2026.06.15 CC Packet - Laserfiche WebLink

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Spheros Environmental | www.spherosenv.com | Page 4 Spheros will use MODFLOW to simulate the flow field and delineate the WHP Areas, and will provide WSB and the City with a cost-effective, flexible, and appropriate model. Once the model is created, the required time-of-travel zones will be used to determine the WHP Areas for the City wells. Pumping rates applied to each well will be based on the maximum daily volume determined from either: 1) the previous 5 years; or, 2) the projected annual pumping over the next 5 years. Following the initial WHPA delineation from this task, Spheros will calibrate the model and complete the sensitivity analysis as required by the MDH. The costs associated with modeling in Task 2 assume the aquifer parameters and hydrogeologic information in the existing NMLG model are reasonably calibrated and significant changes to the conceptual model and aquifer parameters will not be required. Task 3: Conduct Fracture Flow and Surface Water Contribution Area Delineation (if warranted) A fracture flow delineation will be required for the City Wells since the Prairie du Chien and Jordan sandstone aquifers are utilized by the City wells. Even wells solely completed in the Jordan receive flow contribution from the overlying fractured Prairie du Chien dolomite aquifer near the wellfield. The delineation will be based on MDH methodology and reflect a similar approach and assumptions used to complete the previous 2013 plan’s fracture flow delineation. The potential need for a Surface Water Capture Area (SWCA) will be assessed. If needed, it will be delineated based on high vulnerability of the aquifer below surface water features. It is likely that either the DNR’s Level-9 Auto-Catchment watershed boundaries or sewersheds will be used to delineate a SWCA, pending communication with MDH. Task 4: Delineate the DWSMA Following completion of Tasks 1 through 3, Spheros will work with the City and MDH in delineating the boundaries of the DWSMA. The DWSMA includes the surface and subsurface area surrounding the wells and follows the WHPA as closely as possible in accordance with the rules. The boundaries of the DWSMA will be identified using landmarks as defined in the rules. To simplify the City’s management of the resulting DWSMA, particular focus will be on using Minnesota Department of Transportation (MNDOT) road centerlines and quarter section boundaries while also not splitting parcels into multiple parts.