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Page A-S <br /> TASK 4. Evaluation of Potential Sources — Shallow Water Source Alternatives <br /> In this project element, shallow groundwater, such as potentially found in the Middleton Valley and <br /> within the Sangamon River alluvium, and surface waters, such as Lake Tokorozawa and the Vulcan <br /> Materials gravel pits, will be assessed using best available data and professional experience gained <br /> from similar evaluations for Springfield. For the gravel pits, we will review/analyze historic operational <br /> data from past pumping of gravel pits, define minimum allowable water level in gravel pits, with the <br /> goal of estimating a stage-volume relationship for each of the gravel pits. <br /> The unconsolidated aquifer system is composed of thick sequences of clay-rich till, interspersed <br /> with layers of sand and gravel that are naturally variable in thickness and extent. The objective of this <br /> task is to integrate existing information to identify potential areas within the Sangamon River Alluvium <br /> and the Middleton that could support high-capacity wells. Results of the previous tasks will be used to <br /> develop and calibrate a scoping groundwater flow model of the Sangamon Alluvium and the Middleton <br /> Aquifer. The modeling analysis will be used to estimate the 1) potential drought yield of the local <br /> aquifer system at each priority location identified above, 2) appropriate spacing of production wells, <br /> and 3) potential impacts of pumping to neighboring wells. <br /> Subtasks: <br /> 1. Develop stage-volume relationships for gravel pits(Lake Tokorozawa,Vulcan gravel pits) <br /> 2. Assess risk to Lake Tokorozawa water quality from surrounding landfills <br /> 3. Develop cross-sections and "solids" models for shallow aquifers <br /> 4. Develop"scoping" models of shallow aquifers <br /> 5. Estimate yields of shallow options <br /> Results and Products: <br /> • Stage-volume relationships for gravel pits <br /> • 3-D Solids model of Sangamon Alluvial Aquifer and Middleton Valley <br /> • 2-D Geologic cross sections <br /> • Scoping model for assessing potential drought yield of gravel pits and promising locations identified in <br /> the above subtask <br /> • Summary of risk posed to Lake Tokorozawa by surrounding landfills <br />