2018-01-16_PERMIT FILE - M2017036 (2)

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Second Submittal 2.3 Conceptual Model A conceptual groundwater flow model is a graphical, semi-quantitative description of the parameters and conditions that control groundwater flow. Figure 8 displays the conceptual groundwater flow model associated with the Site as limited to the model boundary shown. Components of the conceptual model are represented in the numerical flow model as various boundary conditions and variables. 2.3.1 Boundary Conditions Model Top The top of the conceptual model A defined by the topography(represented by the US digital elevation model, 10 m grid spacing, and Site topographic surveys), and a variable flux boundary. The flux represents natural recharge on non-irrigated areas, and excess irrigation that percolates below the rooting zone in irrigated areas. The bounding condition is assumed to be relatively constant throughout the year as irrigation induced percolation will be attenuated on its vertiL�tl path to the groundwater table. Likewise, naturally occurring precipitation d1-iven percolation is assumed to be constant throughout the year. Model Bottom The bottom of the conceptual model is the Pierre Shale. As described previously,the Pierre shale acts as an aquitard and is therefore represented as a no-flow(i.e.,zero flux)boundary. Perimeter The southern perimeter of the model is the Cache la Poudre River, which is represented as a constant head boundary that varies with time. In the spring and early summer,the height of the river is several feet above its winter flow stage. The height variability is a relative function of the staff gauge height/flow measurements taken at USGS gauging station 06752260. The northern boundary is a flux boundary. Where bedrock outcrops, the flux is minimal, dictated by meteoric shallow groundwater flow through bedrock (mostly shales). As Loveland Ready-Mix Concrete 10 Telesto Solutions,Inc. 20180112_grouwxlwmt lu(ly_zniLsunn,nl.dasx January2018