2018-08-31_GENERAL DOCUMENTS - M1977493

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2016 Reclamation Cost Estimate Update — Climax Mine 2.5 McNulty OSF Subsoil and topsoil to be salvaged from the ultimate footprint of the McNulty OSF will be stockpiled around its perimeter. In accordance with Exhibit E of AM -06 an estimated 921,000 cy of topsoil and/or biosolids will be hauled and placed over the regraded surface for a total of 12 inches of growth medium. After topsoil placement, the lower portion of the OSF (below 11,800 feet) will be seeded with the upland standard seed mixture and higher areas will be seeded with the alpine seed mixture. TR -25 illustrates the final configuration for the stormwater controls on the OSF to be constructed during the reclamation project. These include down drains, perimeter diversion channels, and runoff channels on the reclaimed slope benches. 2.6 Tenmile TSF Tenmile TSF will be reclaimed when it is no longer required for production operations. As approved for Robinson TSF in TR -13, Tenmile TSF will be reclaimed with a combination of dry and wet covers. The majority of the surface will be capped, but a pond is expected to remain over approximately 25% of the top surface (or just over 113 acres). The dry cover area will be capped with a minimum of 12 inches of cover material (likely 6 inches of biosolids or topsoil over 6 inches of subsoil) over 340.5 acres for a total of approximately 550,000 cy. The wet cover area will be capped with a multi -layer system likely to include a geogrid layer similar to that used on the Robinson TSF wet cover area followed by a minimum of 36 inches of cover material (6 inches of biosolids or topsoil over 30 inches of subsoil) over 113.5 acres for a total of approximately 550,000 cy. The area will be seeded with the hydric seed mixture. 2.7 Tenmile Tunnel The Tenmile Tunnel will be sealed upon cessation of mining with concrete bulkheads and slurry backfill since it will no longer be required as part of the site's water management and treatment system. The costs have not changed since the AM -06 update other than an increase for a computational error in the previous cost model. 2.8 3 Dam 3 Dam was reclaimed in its current configuration during the mid-1990s. However, a slight increase in the height of 3 Dam is continuing as a part of production operations which resumed in 2012. This final dam raise will require reclamation at the completion of dam construction with a nominal 12 inches of growth medium (6 inches of biosolids or topsoil over 6 inches of subsoil) resulting in an import of approximately 15,000 cy of material which will be applied to approximately 9 acres of the dam face. The upland standard seed mixture will be applied to the cover material. The AM -06 cost for this project area included an incorrect cost basis for the cover thickness which was not consistent with the reclamation plan described in Exhibit E. This update reflects the corrected cost basis and calculation. 2.9 Pond Shop The Pond Shop itself will be demolished under a different task. However, some basic soil reclamation will still be required at the Pond Shop site. This will include a minor amount of regrading and import of just over 500 cy of topsoil. The upland standard seed mixture will be applied to the cover material. 2.10 Mayflower TSF A portion (244 acres) of Mayflower TSF will be reclaimed when it is no longer needed for production and reclamation operations. However, the southwest portion of Mayflower TSF will be used for water treatment as long as it is necessary to provide detention storage for the water treatment system. A detention storage area and several sludge cells will likely remain on the surface of Mayflower. The eastern portion of the Mayflower TSF will be reclaimed with a dry cover similar to that constructed on the Tenmile TSF. The dry cover area will be capped with a minimum of 12 inches of cover material (likely 6 inches of biosolids or topsoil over 6 inches of subsoil) resulting in an import of approximately 400,000 cy November 2016 (revised August 2018)