2019-07-30_PERMIT FILE - M1996052

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1 r L.G. Everist Combined SWSP Page 5 of 16 March 14, 2018 The net evaporation for the Firestone Pit includes a credit of 0.60 acre-feet of consumptive use of ground water associated with the partial subirrigation of the historically irrigated acreage. No other phreatophyte credit was applied to the other sites. Although depletions estimated in this SWSP assume year-round evaporation depletions, computation of evaporation under this plan may be reduced during periods when the ponds are completely covered by ice. Computation of the net evaporation during any time that the pits are not completely covered by ice shall be determined as the pro-rata amount of the monthly gross evaporation rate distribution amount identified in the State Engineer's General Guidelines for Substitute Supply Plans for Sand and Gravel Pits, subtracting the pro-rata amount of the effective precipitation for that period. The material excavated from the gravel pit areas will be washed on site. The consumptive use of water associated with excavated material is dependent on the location of the material with respect to the water table. According to the "General Guidelines for Substitute water Supply Plans for Sand and Gravel Pits" the product moisture loss is calculated as four percent by weight of mine material excavated below the ground water table and two percent by weight for the mined material excavated above water table. The Applicant anticipates 2018 and 2019 mining production at the Carbon Valley Resource, Firestone Pit and Fort Lupton Sand and Gravel to be 573,651 tons, 1,360,373 tons, and 1,615,904 tons respectively. The quantity mined, and associated depletions, must be tracked separately for water mined above and below the groundwater table. Water used for dust control at Carbon Valley Pit, and Firestone Pit will come from water originally pumped from the pits for dewatering. Water used for dust control at the Fort Lupton Sand and Gravel was previously used from an existing alluvial well, permit no. 57957-F (WDID 0205018 DI TIRRO WELL 2), located outside of the approved slurry wall on the Fort Lupton Pit site. Well permit no. 57957- F is no longer being used for dust control, as Everist has a re-circulating water system at the site where reusable water is pumped from lined cells to wash material and for dust control. Continuous dewatering operations at Carbon Valley Pit, Firestone Pit, and Fort Lupton Pit site are occurring in order to facilitate dry mining conditions. The dewatering water from the water Carbon Valley Pit and Firestone Pit is used for dust control and concrete batching at these pits. All other water pumped from dewatering is returned immediately to the river system. The applicant has performed a lagged water balance for these operations and accounted for the lagged depletions, which is offset by monthly net accretions. Totalizing flow meters have been installed and monthly meter readings showing dewatering volumes were reported on the 2016-2017 submitted accounting and must be reported as part of this SWSP. A stream depletion model using the Glover method was used to calculate the lagged depletions to the River. The alluvial aquifer model uses four aquifer input parameters for each site as follows: 1) X- distance from centroid of the well to the river, 2) W-distance from the aquifer boundary through the well to the river channel, 3) T-transmissivity of the alluvial aquifer (in gallons per foot/day) between the well and the river, and 4) S-specific yield. The following parameters for each site listed in the table below were used in the model: TABLE E - AQUIFER CHARACTERISTICS Site Name T X W S Carbon Valley Pit 50,000 2,000 4,173 0.2 Rinn Valley Pit 125,000 715 4,173 0.2 Firestone Pit 72,300 2,210 2,262 0.2 Fort Lupton Pit 90,000 300 to 1,200 4,500 to 7,996 0.2 Star Water Resources 120,000 558 4,300 0.2