2015-03-20_HYDROLOGY - M1985218 - Laserfiche WebLink

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David Heintz March 20, 2015 Page 2 of 5 DEPLETIONS During this plan year, the maximum exposed surface area total of 17.2 acres within the Active Pit (16.7 exposed acres) and the Unused Wash Pond (0.5 acres). You have submitted an analysis that shows the calculated evaporation, effective precipitation, and resultant net replacement obligation in the attached Tables 1 and 2. You have also performed a depletion analysis based upon the net replacement obligation and the aquifer characteristics to show the lagged depletion schedule to the Arkansas River, as presented in that attached Table 3. The total lagged depletions for this plan year are estimated to be 59.93 acre -feet (57.92 acre - feet from the Active Pit, 1.71 acre -feet from the Unused Wash Pond, and 0.3 acre -foot from the sanitary/ miscellaneous well). During the April 1, 2015 through March 31, 2016 plan year, the site excavations will not expose any additional ground water. No mining or dewatering will take place during this plan year unless an amendment to this plan is approved. Stream depletion analyses for both the Active Pit area and the Unused Wash Pond (attached) used the Stream Depletion Factors of 7.3 days for the Active Pit and 120 days for the Unused Wash Pond, obtained from the USGS Publication 72 -192 "Stream Depletion Factors, Arkansas River Valley, Southeastern Colorado ". For the purpose of this SWSP approval, it was assumed that the well operating under Permit No. 66042 -F has, and will continue, to pump at a steady state condition; therefore, no lagging was analysis was performed to calculate the stream depletion. Please note this is the last plan approval that lagging analyses utilizing Stream Depletion Factors obtained from USGS Publication 72 -192 will be allowed without justification of the method; otherwise, please utilize lagging analyses which incorporate methods that are physically relevant to this site (ie a Glover analysis with no flow boundary) in all future plan renewals. REPLACEMENTS The source of replacement water is the Arkansas Groundwater Users Association ( "AGUA "), and the 1 -year lease agreement covering this plan year. The amount of the lease water is for 61 acre -feet of fully consumable water. This volume of water will be delivered to a point on the Arkansas River in Section 34, Township 20 South, Range 63 West of the 6th P.M., which is directly adjacent to the Rich Pit; therefore, transit losses will not be assessed. The lease with AGUA will provide sufficient replacement water for depletions at the Rich Pit over the plan year, and will be delivered according to the schedule outlined in Column 5 of the attached Table 3. A copy of the 1 -year lease agreement dated February 2, 2015 and covering the period April 1, 2015 - March 31, 2016 is attached. In accordance with the letter dated April 30, 2010 from the Colorado Division of Reclamation, Mining, and Safety ( "DRMS "), a source of renewable long -term replacement water sufficient to cover evaporative depletions has not been secured for this plan. At this time Martin Marietta plans to proceed with the option to mitigate long -term injurious stream depletions that result from mining- related exposure of groundwater according to the original plan submitted by LaFarge to install a slurry wall liner for use as water storage for lining and /or backfilling the pit. The Rich Pit has a bond totaling $344,500 to cover the cost of the remediation (Bond No. 44284559). of - c 1313 Sherman Street, Room 821, Denver, CO 80203 P 303.866.3581 F 303.866.3589 www.water.state.co.us I y� 01 1876: