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Red Creek Quarry, Groundwater Modeling Analysis <br /> <br /> <br /> <br />12 <br />DRAFT for review purposes only. Use of contents on this sheet is subject to the limitations specified at the beginning of this document. <br />RedCreekQuarry_Modeling_TM_DRAFT_20230911 <br />Visual field observations were conducted on Red Creek in December 2022. The steady-state EC model was <br />also calibrated to the visual observations of flow conditions in Red Creek. <br />Table 1 shows the December 2022 field observations compared to the EC model projections. Reaches that <br />were dry in December 2022 are also seen to be dry in the EC model results. In reaches that have minimal <br />surface water present in December 2022 (reaches 7 and 8), there is less water present in the EC model re- <br />sults than compared to reaches with surface water present (reaches 5 and 6) (Table 1). Reach 1 is located <br />at the model boundary closer to the Arkansas River and receives some boundary effects, contributing to a <br />higher rate of groundwater entering the creek (Figure 4, Table 1). <br /> <br />Table 1. Red Creek Existing Conditions <br />Creek Reach December 2022 <br />Visual Creek Observation <br />EC Model –May 2023 GW table - Rate <br />of groundwater added to stream <br />(ft3/day) <br />1 Unknown 1854 <br />2 Unknown 646 <br />3 Dry 66 <br />4 Unknown 51 <br />5 Surface Water Present 230 <br />6 Surface Water Present 136 <br />7 Minimal Surface Water Present 47 <br />8 Start of Surface Water 9 <br />9 Dry 0 <br />10 Dry 0 <br />11 Dry 0 <br />3.2 Projected MPO Mine Block Groundwater Accumulation <br />The transient groundwater flow model for each mine block estimates the rate of groundwater entering each <br />mine block during the 10-year period as discussed in Section 2.7. Table 2 summarizes the projected rate of <br />groundwater entering each mine block. As mentioned in Section 1.4, the first two mine blocks have an addi- <br />tional defined smaller, deeper pit 15-feet into the Codell Sandstone. This is represented in Table 2 for Mine <br />Block 0 to 10 and Mine Block 10 to 20. Subsequent mine blocks are at least 15-feet below the top of the <br />Codell Sandstone in the southern portions of each mine block and therefore do not require the additional <br />area be modeled explicitly. <br />If the elevation of a mine block bottom is above the interpolated water table, the mine block will have no <br />simulated groundwater flow in and will be dry. Mine blocks following Mine Block 20 to 30 are seen to have <br />no groundwater entering the pit floor due to the elevations of the mine block being above the interpolated <br />water table (Table 2). These mine blocks are located in the central, southern, and eastern portions of the <br />site where the interpolated water table has the greatest uncertainty due to lack of monitor wells (Figure 2). <br />The main portion of Mine Block 10 to 20 has an elevation above the water table and is therefore dry, but the <br />additional deeper sandstone pit has an elevation below the water table and thus has a rate of groundwater <br />entering the pit (Table 2). The greatest rate of groundwater entering a mine block is seen in Mine Block 20 to <br />30 (Table 2).