2021-09-09_REVISION - M2004044 (10)

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The active mining face will extend no more than 2,300 feet in length. During mining and prior to reclamation in the West and East Areas, the mine walls will be a nearly vertical to '/2H:1V slope (see Exhibit C, Mining Maps). Mining will progress down to the depth of quality aggregate material. Backfilling and/or grading of side slopes may follow behind the mining activities before mining in the Area is complete. Concurrent reclamation will be practiced when the highwall reaches the mine limit. During the flood season April 1 through September 30 and when the highwall is within 400 feet or less of the river the highwall will be no steeper then 3H:1V. As mining progresses, topsoil, overburden, and non-marketable materials will be removed and stockpiled for use in reclamation activities. Overburden from the West Area and East Areas will be used in reclamation. Should there be excess overburden on these cells, the material will be conveyed to the Platte Valley site for reclamation or to be sold. During mining in the West and East Areas, topsoil will be segregated and stockpiled in the locations shown on Exhibit C Mining Maps, i.e. outside of the Floodway. As mining progresses, overburden will be taken directly to mined out slopes for use in reclamation. Topsoil and overburden stockpiles will be configured to have side-slopes no steeper than 3H:1 V. If the stockpiles are inactive for more than one growing season, such as the stockpiles used for screening, they will be seeded with the fast-growing grass seed mixture below. Stockpile Grass Seed Mixture Grass Species Rate (#PLS/ac Luna Pubescent Wheatgrass 15.0 Amur Intermediate Wheatgrass 15.0 Rates are for broadcast seeding. Other than those used for screening, long-term stockpiles are not anticipated. Temporary stockpile materials will continually be used for reclamation and the stockpiles will likely be disturbed on a frequent basis and seeding the stockpiles may not be practical during the operation. If stockpile seeding is not used, surface roughening will be maintained to limit wind and water erosion. Most of the proposed Tucson South Resource Permit Boundary Area is within the regulatory floodplain of South Platte River. Because of floodplain regulatory restrictions, stockpiling will occur within a mining Area whenever possible with the top of stockpile elevation lower than the pre-project grade. Stockpiles within the modeled floodplain above the existing ground surface will generally be created parallel to potential South Platte River flood flows. The stockpiles will be no longer than 300 feet, with minimum spacing of 100 feet between stockpiles for flood flows to pass (see Exhibit C, Mining Maps). The screening stockpiles along Highway 7 as Aggregate Industries—Tucson South Amendment—MLRB 112 Permit Application Exhibit D-6