2022-03-25_HYDROLOGY - M2017036 - Laserfiche WebLink

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Knox Pit SWSP January 19, 2022 Plan ID 5958 Page 4 of 8 for this plan period. Consumptive use due to evaporation (including truck washing and dust control) and production purposes at the site will therefore total 42.65 acre-feet durin� this ptan period. Lagged Recharge/Depletions The Phase 1 £t 2 Sump, as shown on the attached Figure 3, is tocated closer to the river than the Water Management Pond where dewatering water will be placed for recharge. Therefore, it cannot be assumed that the depletions from dewatering are offset by deliveries to the Water Management Pond. The depletions from pumping of the Phase 1 �t 2 Sump for dewatering purposes and the accretions for recharge from the Water Management Pond were calculated using the Alluvial Water Accounting System (AWAS) program developed by the Integrated Decision Support (IDS) Group at Colorado State University with the alluvial aquifer boundary condition. The monthly groundwater depletions were lagged from the Phase 1 �t 2 Sump to the Cache la Poudre River in the SW'/a of the NW '/a of Section 32, Township 8 North, Range 69 West, 6`h P.M. using the following parameters: • Distance from the Phase 1 £� 2 Sump to the river (X) = 3,270 feet • Distance from the river to the no-flow boundary (W) = 6,000 feet • Specific yield (S) = 0.20 • Transmissivity (T) = 50,000 gallons per day per foot The AWAS model was utilized to develop a unit response function (URF) to estimate monthly tagged depletions to the river. The monthly groundwater accretions from the Water Management Pond were catculated as the amount of water pumped for dewatering purposes, minus the operational and evaporative consumptive use of water at the site as described above. The volume of the "first fill" associated with the dewatering and completion of excavation of the Water Management Pond was accounted for by subtracting 53.37 acre-feet from the volume of groundwater considered to be recharged to the aquifer for the month of July 2022. The resulting accretions were lag�ed from the Water Management Pond to the same point on the Cache la Poudre River in the SW'/a of the NW�/a of Section 32, Township 8 North, Range 69 West, 6`h P.M. using the following parameters: • Distance from the Water Management Pond to the river (X) = 4,250 feet • Distance from the river to the no-ftow boundary (W) = 6,000 feet • Specific yield (S) = 0.20 • Transmissivity (T) = 50,000 gallons per day per foot The AWAS modet was utilized to develop a unit response function (URF) to estimate monthly lagged recharge accretions to the river. After accounting for recharge accretions, you have calculated lagged depletions resulting from operations at the site to total 69.35 acre-feet for this plan period as shown on the attached Figure 7. Using the previousty provided URFs, past accounting submittals, and projected depletions/rechar�e for this plan period, the SEO has calculated lagged deptetions to total 76.60 acre-feet for this plan period.