2013-05-29_HYDROLOGY - M1999120 - Laserfiche WebLink

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Mr. Rick Parsons, P.E. L.G. Everist Combined SWSP Amendment 1 Page 4 of 9 May 28, 2013 ice covered period (the months of January, February and December) for any time that the pit is not completely covered by ice. Computation of the net evaporation during any time that the pit is 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 pits is estimated to be approximately 72 percent below the water table and approximately 28 percent above 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 2012 mining production at the Lohmann Pit, Rinn Valley Pit, and Lupton Meadows Pit to be 150,000 tons, 550,000 tons, and 1,250,000 tons respectively. For 2013, production at these same sites are anticipated to increase to 175,000 tons, 575,000 tons, and 1,300,000 tons respectively. Water used for dust control at Lohmann Pit and Rinn Valley Pit will come from water originally pumped from the pits for dewatering. Water used for dust control at the Fort Lupton Pit and the Lupton Meadows Pit will come 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 permitted to provide water for concrete batching and dust suppression. The depletions resulting from pumping the well, for those uses, will be replaced under this plan. 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 Lohmann 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 1,200 7,996 0.2 Lupton Meadows Pit 90,000 300 4,500 0.2 Dewatering Continuous dewatering operations at Lohmann, Rinn Valley, and Lupton Meadows Pits are occurring in order to facilitate dry mining conditions. This water is used for dust control at the Lohmann and Rinn Valley pit, and is used for concrete production at the Rinn Valley pit. All other water pumped for dewatering is returned immediately to the river system to provide accretion credits to offset lagged dewatering and mining operation depletions. The applicant has performed a lagged water balance for these operations and account for the lagged depletions which is offset by monthly net accretions. If not already installed, totalizing flow meters must be installed and monthly meter readings showing dewatering volumes must be reported on the submitted accounting. Future SWSPs will not be approved unless such meters have been installed. After March 31, 2012, the operator cannot claim credit for dewatering accretions that exceed lagged dewatering depletions unless such meters are installed.