2020-05-28_HYDROLOGY - M2001005 - Laserfiche WebLink

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�, l BIRISS May 28, 2020 ��Iagef DEPLETIONS The depletions from this operation for the 2020 plan year (April 20, 2020 through March 31, 2021) consist of 146.42 acre-feet of net evaporative loss from a maximum of 51.1 acres of exposed ground water, 30 acre-feet for irrigation uses (6.67 acre-feet on 10 acres in Phase 1 and 23.33 acre-feet on 35 acres in Phase 2), 3.50 acre-feet pumped for dust suppression, and 185.16 acre-feet of groundwater infiltrating into the Phase 2 pit during the first fill. The depletions from this operation for the 2021 plan year (April 1, 2021 through March 31, 2022) consist of 154.84 acre-feet of net evaporative loss from a maximum of 51.1 acres of exposed ground water, 30 acre-feet for irrigation uses (6.67 acre-feet on 10 acres in Phase 1 and 23.33 acre-feet on 35 acres in Phase 2), 3.5 acre-feet pumped for dust suppression, and 24.03 acre-feet of groundwater infiltrating into the Phase 2 pit. A monthly breakdown of these amounts for both plan years is shown in Table 1, attached. Total depletions from mining activities are estimated to be 365.08 acre-feet for the 2020 plan year and 212.37 acre-feet for the 2021 plan year. An estimated 348.42 acre-feet will be required to fill the Phase 2 pit. Initially, all inflows to the Phase 2 pit will occur by groundwater infiltration. As of March 2020, 139.24 acre-feet of groundwater has already infiltrated into the Phase 2 pit. Based on collected data, groundwater infiltration may occur at a rate of up to 270 gpm, but is generally expected to be less than 200 gpm. In the future, a turnout structure may be constructed to fill the pit directly from the Lester-Attebery Ditch. These deliveries will be separately metered and associated depletions will be assessed the same day that the deliveries occur. LAGGED DEPLETIONS The renewal request has included lagged depletions associated with evaporation, irrigation, dust control, and the Phase 2 pit first-fill. Evaporative depletions were lagged individually from each pond based on the exposed ground water area, irrigation and dust control depletions were lagged from the fresh water supply pond, and depletions from first-fill operations were lagged from the centroid of the Phase 2 mining area. For the most conservative estimate, the first-fill was assumed to be a result of groundwater infiltration without any volume from the Lester-Attebery Ditch. The depletions were lagged through use of IDS-AWAS, which utilized the Glover Method with the following parameters: Glover Method Input Parameters Location T S X W Phase 1 40,000 0.087 934 11489 Phase 2 40,000 10.087 541 1,252 T = Transmissivity of aquifer (gallons per day per foot) S = Specific yield of aquifer X = Distance between the centroid of the pond or mining area and the Arkansas River (feet)