2014-05-23_HYDROLOGY - M1998013 - Laserfiche WebLink

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Mr. Andy Rodriguez, P.E Shores SWSP Page 2 of 5 must comply with the requirements of the Colorado Reclamation Act and the Mineral Rules and Regulations for the protection of water resources. The April 30, 2010 letter from DRMS requires that you provide information to DRMS to demonstrate you can replace long term injurious stream depletions that result from mining related exposure of ground water. The DRMS letter identifies four approaches to satisfy this requirement. In accordance with approach nos. 1 and 3, you have obtained a bond for $1,607,800 through DRMS for lining or backfilling of the exposed ground water. Depletions Currently 11 acres of ground water surface is exposed at the Shores Pit within the silt pond. The net depletion of ground water due to evaporation from these 11 acres is calculated to be 30.66 acre -feet for this plan period. Net evaporative depletions were calculated using a gross annual evaporation of 42 inches from the exposed water surface, with an annual credit of 10.56 inches for effective precipitation. The applicant has not requested ice cover credit under this plan. Ground water from the 11 acre silt pond is used for dust control and concrete batching. The Applicant estimates that 1.66 acre -feet of water per year (1.93 acre -feet for this plan year) will be used for dust control. Approximately 118,589 cubic yards of concrete will be batched onsite during this plan period at a depletion of 40 gallons per cubic yard, resulting in a water requirement of 14.55 acre -feet. However the plant utilizes a water tap for the concrete batching at a rate of 4 million gallons per year, or 14.32 acre -feet during this plan period. Therefore the resulting annual net depletions from concrete batching is 1.64 acre- feet.The water supplied by Central Weld shall be metered along with the total water used for onsite concrete batching to aid in calculating the actual depletions owed. The data from both metered sources shall be included in the accounting provided to the Division Engineer. The Applicant also anticipates that 570,356 tons of aggregate will be mined during this plan period. The material is mined within the slurry wall area of Cell D therefore there are zero depletions associated with the mined material. The net evaporation and operation depletions associated with the Shores pit are estimated to be 34.24 acre -feet, as shown in the attached Table 2. Dewatering of the site commenced in February 1999 at a rate of 300 gallons per minute and had remained constant during mining of cells A, B, C, and D. For modeling purposes dewatering was stopped on December 2007 which is the year the slurry walls for the three cells were completed. As long as dewatering operations in cell D remain constant, it is assumed that the accretion credits are sufficient to offset any lagged depletions as this water is not used and immediately returns to the stream. The SWSP accounts for the net depletions at the river that occur due to the past dewatering operations (February 1999 through December 2007) The lagged depletions from past dewatering at the site during the period of this plan total 17.83 acre - feet. The depletions from evaporation, water removed in the mined product, dust suppression, concrete batching and dewatering were lagged to Saint Vrain Creek using a Glover analysis. The following parameters were used in the model to lag operational and evaporative losses: transmissivity (T) = 72,300 gallons per day per foot, specific yield (SY) = 0.2, the distance from the exposed ground water to the creek (X) = 5,409 feet, and the location from the parallel 1313 Sherman Street. Room 821, Denver, CO 80203 P 303.866.3581 F 303.866.2223 www.water.state.co.us