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5.1,8 <br />During the course of Well 7 pumping, Well 8 at a distance of 2400 feet observed approximately 6- <br />9 feet of drawdown. <br />The Theis equation predicts a cone of depression approximately 2448 feet from pumping well 7. <br />Theis Equation for the City of Ramsey <br />Time = <br />0.5 <br />days <br />Theis W(u) Function <br />0,752 <br />unitless <br />Drawdown = <br />6 <br />ft <br />Transmissivity = <br />11493 <br />gpd/ft <br />Pumping Rate = <br />800 <br />gpm <br />Theis u variable = <br />0.390 <br />unitless <br />r2 = 4Ttu 4S <br />Storativity = <br />0.0002 <br />unitless <br />Radius rounded for <br />map <br />2400 <br />ft <br />These results indicate that a single well pumping at current well field spacing does not induce <br />mutual well interference. This 6 foot cone of depression is depicted on Figure 11. <br />However, complexities arise as present day conditions see the use of 3 — 5 concurrent wells, and <br />a 2040 demand increasing up to a projected 500% daily maximum demand. In order to model <br />these scenarios and their resulting cone of depressions a groundwater model was developed. <br />Model <br />The groundwater flow and cone of depression calculation for the City of Ramsey were <br />determined using an existing regional MODFLOW model that was developed by Barr Engineering <br />Company for the Metropolitan Council (Metro Council, 2014). MODFLOW is a 3D, cell -centered, <br />finite difference, saturated flow model developed by the U.S. Geological Survey (McDonald and <br />Harbaugh, 1988: Harbaugh et al., 2000), <br />MODFLOW was developed by the United States Geological Survey and is publicly available. The <br />specific software code used for this delineation was MODFLOW-2005 (Harbaugh, 2005), The <br />program has been thoroughly documented, is widely used by consultants, government agencies, <br />and researchers and consistently accepted in regulatory proceedings. MODFLOW is also an <br />extremely versatile program capable of simulating groundwater flow in up to three dirnensions <br />while offering a variety of boundary condition options, confined or unconfined aquifer conditions <br />and allowing for vertical discrelization through the use of layering <br />The Metro Model consists of nine layers that represent the major aquifers and aquitards within <br />the seven -county metropolitan area. These layers represent, from top to bottom (youngest to <br />oldest), the following units: (1) surficial aquifer of glacial deposits; (2) St. Peter Sandstone or <br />Quaternary Buried Artesian Aquifer; (3) Prairie du Chien Group; (4) Jordan Sandstone; (5) St <br />Lawrence Formation (aquitard); (6) Tunnel City Group; (7) Wonewoc Aquifer, (8) Eau Claire <br />Formation (aquitard); and (9) Mt. Simon Sandstone. The regional groundwater model was <br />calibrated to steady-state water levels and river base flows_ Model parameter development and <br />error is discussed in the Metro Model report. <br />FEASIBILITY STUDY -DRAFT RAMSY 154354 <br />Page 21 <br />