2025-12-12_HYDROLOGY - M1977023 - Laserfiche WebLink

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Peter Foster and Jonah Howe, Wright Water Engineers Page 5 of 14 Re: Gunnison West Gravel Pit SWSP, Amendment No. 1 December 12, 2025 month applied to the haul roads during the period from May through October. Dust control at the site is estimated to be 1.3 acre-feet/ year, as shown on attached Table 2. Aggregate Production A maximum of 100,000 tons of aggregate will be mined per year. Aggregate will be mined in a dewatered state and washed; therefore, product moisture loss is assumed to be four percent (4%) by weight of the mined material. Water lost in mined product and from washing is 2.9 acre-feet/year, as shown on attached Table 2. Dewateri ng Dewatering is proposed to occur continuously during the term of this SWSP, therefore, depletions from dewatering are assumed to be offset by the dewatering discharge to the stream. In the event dewatering will cease and the mined area is allowed to refill during the term of this SWSP, the Applicant will develop a stage-volume relationship for the actively mined area and these depletions will be added to the total depletions from the mining operation and included on accounting provided to the Division Engineer and Water Commissioner. An example pit filling accounting sheet is included as Table 5. Replacement Replacement Water The proposed source of replacement water for this pit during the irrigation season (April through October) is a portion of the Applicant's interests in the Seventy-Five Ditch (WDID 5900668). The Seventy-Five Ditch diverts water from the Gunnison River and was decreed in Civil Action No. 1325 (Priority No. 1) for 14 cubic feet per second ("cfs") to irrigate 560 acres, providing a duty of water of 1 cfs per 40 acres of land. United owns thirty-one percent (31%) of the senior water right in the Seventy-Five Ditch, or 4.33 cfs, which is proposed to be used as a replacement water source in this SWSP. Based on