2016-02-17_HYDROLOGY - M2006003 (3)

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Mr. Andy Rodriguez, P.E. Page 2 of 6 Bestway's Brighton Combined SWSP February 10, 2016 which can be used to line the respective pits in the unforeseen event, or events, which would lead to the abandonment of the Pits. Depletions Approximately 6.5 acres of open water surface is present at the Parker-Dersham Pit (contained outside of the approved slurry wall) (Figure 1). Net evaporative depletions were calculated using a gross annual evaporation of 45.5 inches from the exposed water surface, with a credit of 10.19 inches for an effective precipitation amount of 35.32 inches per year. No phreatophyte credit has been applied to this plan. The net depletion of ground water due to evaporation from Parker-Dersham Pit is 19.15 acre-feet as shown on the attached Table 1. The Applicant has stopped mining at the Parker-Dersham Pit site and is in the process of reclaiming the disturbed areas. No mining will occur at the Baseline Pit site or Parker-Dersham Pit site during this plan period, as the Baseline Pit site is in the processed of being reclaimed, the southwest corner of the Parker-Dersham Pit site and the Dersham property has been reclaimed and taken over the City of Aurora, and the remaining portion of the Parker-Dersham Pit site located in the northwest corner is currently being backfilled. An estimated 3.24 acre-feet of water from the Baseline Site plant well (permit no. 75087-F, WDID 0210141) will be used at the combined pits for on-site dust control during this plan period. This well will also be used to support concrete production. It is estimated that 133,599 cubic yards of concrete batching will occur and that 40 gallons of water will be consumed per cubic yard of concrete production. This leads to 16.40 acre-feet of water to be used for concrete production at the combined pits. The amount diverted from well permit no. 75087-F shall be metered and depletions from this well are 100 percent consumptive. The combined evaporative and operational losses at these sites will equal 38.79 acre- feet during this plan period. The depletions from the mining operation were lagged to the South Platte River using the SDF method. The construction of the slurry wall at the Baseline Resource site affects the timing of the lagged impacts on the South Platte River. The applicant previously prepared a numeric model to account for this effect. According to the model, the SDF for the evaporative loss was estimated to be 205 days and the SDF for the plant well is estimated to be 176 days. The total lagged depletions to be replaced during 2015 are projected to be 37.96 acre-feet as shown on Table 1. Replacements The proposed source of replacement for this pit is nontributary ground water pumped from an existing Laramie-Fox Hills aquifer well and fully consumable effluent leased from the City of Aurora. The nontributary Laramie-Fox Hills aquifer water will be withdrawn by an existing well pursuant to permit no. 64750-F. Additional information regarding the well is shown below: Well Field WDID None Well Field Name None Relevant Water Right Case Number None Well WDID 0210166 Well Name Hall Irwin LFH 64750-F Relevant Well Permit 64750-F Well Location NEI/a, NE'/a, SEI/a, Sec 36, T1 N, R67W, 6 P.M. Aquifer Laramie-Fox Hills