2014-06-20_REVISION - M1981207 (10)

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Blue Pit 112 Permit Amendment Site Map and Grading Plan The erosion control measures to be installed are shown on Map F which is located in Appendix B. The final grading of the site is shown on Map F. The final slopes of the site will be 3H:iV for Mining Areas 2 and 3. Mining Area 1 of the existing operation will be reclaimed to minimum of 2.5H:iV. As described above, a small 2.o' berm will be installed on the northwest and east side the mining area assure that no runoff from the irrigated pasture enters the pit as shown on Map C -2B and Map F. Drainage Structures There are no drainage features that will enter the Blue Pit reclaimed area. The berm on the north portion of Mining Area 2 will be left in place to reduce runoff to the reclaimed slope. Surface water runoff will also be intercepted by the Spring Ditch in the northeast portion of the permit area. A 2.0 feet high berm will also be left in place on the eastern edge of the permit area to prevent runoff from entering the pit from this direction. The Basin Ditch will have an open ditch to move the water, as shown on Maps C -2A and B. A small area north of the expansion area could potentially drain to the pit but a small berm will be installed, as shown on Map F to prevent this inflow. The berm will direct these undisturbed flows to the west. All surface water runoff from the disturbed area drains to the pit floor and will not leave the site. Construction Schedule The majority of the erosion and sedimentation control features will be installed on the reclaimed slopes. The reclaimed slopes will be created as areas become available over the next 10-30 years. The temporary revegetation of the topsoil pile will be within 6 months of the topsoil being placed. No immediate backfilling of slopes in area 1 can take place or occur since the area is used to the facilities area. Permanent Stabilization Permanent stabilization of the slope areas will be achieved through seeding with the rangeland slopes. Also the stormwater catchment benches will be installed with a concrete lined ditch for the water to get to the pit floor at key locations. See design details on following pages. See Map F. Permanent stabilization of the irrigation areas will be through seeding with the irrigated pasture seed mix and installation of irrigation system. The Blue Pit is an elevated terrace above the Roaring Fork River Valley. There are no streams that enter the site and there will be no surface water that leaves the site after reclamation. Surface runoff from above the site is captured by the Basin Ditch, the 2 foot berm left in place and the Spring Ditch and will continue to do so after reclamation. All disturbances are graded to the pit floor which is sufficient to hold a ioo year event that drains to the permit area. Additionally, the material of the pit floor is very porous because it consists of large gravelly material. Stormwater that is encountered within the pit will infiltrate to the groundwater as it does today. The reclaimed 3H:1V side slopes will have stormwater catchment benches which will prevent erosion. The stormwater catchment benches will be graded to one of three grouted channels to take the water from the slope to the pit floor. All post- mining drainage features are shown on Map F (Reclamation Plan Map). Blue Pit May 2014 G -2