2017-03-22_HYDROLOGY - M1985218 - Laserfiche WebLink

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David Heintz March 22, 2017 Page 2 of 4 However, it is expected that lagged depletions from the Unused Wash Pond will continue to accrue during this plan year. During the April 1, 2017 through March 31, 2018 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. Plans in previous years utilized stream depletion factors obtained from the USGS Publication 72-192 “Stream Depletion Factors, Arkansas River Valley, Southeastern Colorado”. However, for this plan approval a Glover analysis was utilized to determine lagged depletions to the stream from the consumptive use of ground water described above. The Glover analysis utilized the following parameters: ● Transmissivity – 80,000 gallons/day/foot ● Storage Coefficient – 0.20 ● Distance to the Stream –864 feet ● Distance to No-Flow Boundary – 4,121 feet Based on these parameters, modeling was prepared for the exposed surface area from April 2017 through March 2018 as shown in Table 1. The lagged depletion analysis uses the previously used approach to account for all lagged depletions prior to March 2016. According to the analyses, 61.96 acre-feet of lagged depletions will occur during this plan year. This total is made up of 61.25 acre- feet of depletions due to the Active Pit, 0.38 acre-feet of depletions due to past use of the Unused Wash Pond and 0.333 acre-feet of depletions from the Sanitary Well (see Table 3). 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 62.7 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 January 4, 2017 and covering the period April 1, 2017 – March 31, 2018 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 ground water 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). CONDITIONS OF APPROVAL I hereby approve the proposed SWSP in accordance with §37-90-137(11), C.R.S., subject to the following conditions: 1. This current plan shall be valid April 1, 2017 through March 31, 2018 unless otherwise revoked or superseded by decree. Should an additional SWSP be requested, such renewal