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MINING AND RECLAMATION PLAN MT. GUNNISON N0. 1 MINE • 3.5.2 Portals and Entries January, 1986 Temporary Abandonment - In the event that the mine entry must be rendered temporarily inactive, the opening shall be protected by barricades or other covering devices, fenced, and posted with signs identifying the nature of the hazard. The fences, barricades, and signs shall be periodically inspected and maintained in good operating condition until mining activities or monitoring work are resumed. Permanent Abandonment - Upon permanent abandonment, the mine will be permanently sealed to prevent access to the mine workings by people, livestock, wildlife, machinery, and to keep acid or other toxic drainage from entering ground or surface waters. It is anticipated, based on water quality data in this Mining and Reclamation Plan, that the mine drainage will be of dischargeable quality. In this instance, the entries will be sealed in a manner to allow drainage through the • seal and prevent the water from building up behind the seal. Should the drainage prove to be toxic, an alternative sealing plan is presented and has been designed to prevent the drainage from infiltrating ground or surface waters. In either event, the first few courses of tunnel liner plate and steel ribs, as well as the concrete structures, will be removed and the surface regraded in accordance with Section 4.3 of this Mining and Reclamation Plan. Non-Toxic Discharge - In the event that the drainage is non-toxic, a concrete wall 8 to 12 inches thick will be constructed in each main entry in solid coal just inby the portal tunnels (Exhibits 3.5.2.A, B, and C) and ventilation entries (Exhibit 3.5.2D). The entries will be timbered on each side of the wall to prevent excessive loads from bearing upon the concrete wall. The entries and portal tunnels will be backfilled with dirt from the wall out to the surface. Drain pipes comprised of 4 inch diameter schedule 40 PVC pipe will be installed through the concrete wall and backfilled to allow drainage through the seal. The design is based on a U. S. Environmental Protection Agency publication entitled Inactive 8 Abandoned Underground Mines, Water Pollution Prevention and Control. As mentioned above, the first few courses of linear plate and steel ribs and the concrete portal structures will be removed and the surface recontoured. 3-81