2012-05-22_HYDROLOGY - M1985218 - Laserfiche WebLink

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Mr. Stephen Buechner Page 2 May 21, 2012 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 59.28 acre -feet (56.54 acre -feet from the Active Pit, 1.73 acre -feet from the Unused Wash Pond, and 1 acre -foot from the sanitary /miscellaneous well). During the April 1, 2012 through March 31, 2013 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 ". REPLACEMENTS The source of replacement water is the Arkansas Groundwater Users Association ( "AGUA "), and the 1 -year lease agreement covering this plan year has been submitted as verification to this office. The amount of the lease water is for 60 acre -feet of fully consumable water, commencing April 1, 2012. Per the lease agreement, 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 E of the attached Table 3. A new lease agreement must be provided for any renewal of this SWSP in the coming years. In accordance with the letter dated April 30, 2010 (copy attached) from the Colorado Division of Reclamation, Mining, and Safety ( "DRMS "), all sand and gravel mining operators 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, or provide bonding for an alternative method to mitigate, the long term injurious stream depletions that result from mining related exposure of ground water. A source of renewable Tong -term replacement water sufficient to cover evaporative depletions has not been secured for this plan. In a letter dated April 28, 2011, Lafarge notified DRMS that it was considering bonding the site to install a slurry wall liner for use as water storage, with a preliminary estimated cost of $271,320. At this time Martin Marietta plans to proceed with this option to mitigate log -term injurious stream depletions that result from mining - related exposure of groundwater. Martin Marietta anticipates that it will have up to three years to phase in the additional financial warranty. The Rich Pit is currently bonded for $51,542 with the DRMS. Future SWSPs for this site will not authorize any additional use of ground water until the Applicant provides documentation that a bond sufficient to cover lining or backfilling of the pit has been obtained.