2019-07-09_REVISION - M2004044 (30)

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Evaporative losses at the site are attributable to groundwater exposed in the dewatering trenches in the West and East cells(Phases 2 and 3),groundwater exposed in the settling pond, and groundwater exposed as a result of wet mining in the South cell(Phase 1). The dewatering trenches will be constructed following completion of the slurry walls surrounding the West and East cells. The maximum exposed surface area during the life of the mine is equal to the combined total mined area of the South Cell(Phase 1),the dewatering trench surrounding the West cell (Phase 2), and the settling pond associated with the West cell. The maximum exposed surface area during the life of the mine is estimated at 18.5 acres. Additional exposed groundwater from the old Tucson Pit(DRMS Permit No. M- 1991-140)has been incorporated into the permit boundary of the Tucson South Pit. Therefore,the maximum exposed groundwater allowed pursuant to the approved well permit is 25 acres. Evaporative losses were calculated as the difference between gross evaporation and effective precipitation. The NOAA Technical Report NWS 33, Evaporation Atlas for the Contiguous 48 United States(U.S. Department of Commerce)was used to determine gross evaporation;the average annual gross evaporation for this site was determined to be 43 inches. Precipitation was obtained from the Colorado Climate Center for the Brighton weather station. The gross annual precipitation for this site was determined to be 14.55 inches. Effective precipitation was calculated as 70 percent of gross precipitation;thus,the average annual effective precipitation was determined to be 10.19 inches. The maximum total annual evaporative consumptive use at the site is estimated at 68.25 acre-feet. The maximum annual production at the site is estimated at 1.25 million tons. The anticipated maximum volume of water lost in the material hauled off-site is 60 acre-feet per year. Maximum dust control requirements at the site are estimated at 5.0 acre-feet per year. The mine will be at the highest production during the months of May through August, and in combination with the weather,this period will require the greatest amount of dust control: The mine will be in production year-round and therefore dust control may be required during all months. The maximum annual operational water consumptive use due to the mining operation is estimated at 65 acre-feet per year. The maximum annual consumptive use from mining at the site authorized by the well permit is 133.25 acre-feet per year as shown in the following table. Evaporation 68.25 acre-feet Moisture Retained in Product 60.00 acre-feet Dust Control 5.00 acre-feet Total 133.25 acre-feet It is not anticipated that additional water will be required for reclamation of the site. Once reclamation is completed the City of Aurora will use decreed water rights to fill the ponds. (4) The Operator/Applicant shall indicate the projected amount from each of the sources of water to supply the project water requirements for the mining operation and reclamation. Aggregate Industries(AI)currently maintains a substitute water supply plan approved through the Office of the State Engineer for its mining operations along the South Platte River and its tributaries. Until the liners surrounding the West and East cells of the project have been approved by the State Engineer, and the South cell has been fully reclaimed, replacement water will be provided pursuant to Al's Combined Substitute Supply Plan(CoSSP). The plan includes this site. Sources of water currently included in the CoSSP include historic consumptive use credits from several area irrigation ditches,water from the City of Westminster, and other water currently available to Al under existing lease agreements. Under the CoSSP, replacements are made to the South Platte River at various locations including the Metro Wastewater Treatment Plant outfall structure located upstream of the property. Transit loss associated with Aggregate Industries Tucson South Resource Permit#M-2004-044112 Permit Amendment Page G-3