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-57- WECC proposed, within the amended permit revision application, to construct a five million ton coal processing waste pile. The refuse would consist of coarse coal reject and development waste rock. The mine projects waste production at a rate of 150,000 tons for the first year and 100,000 tons per year thereafter. The completed upper waste pile structure would cover approximately 40 acres, and attain a maximum thickness of 160 feet. The waste pile would have 2.5 H:1V (horizontal to vertical) facial slopes with 30 foot wide benches at 50 foot vertical intervals. The overall final facial slope will be approximately 3 H:1V (horizontal to vertical slope of approximately 18.2 degrees) in order to facilitate reclamation. Samples of currently produced waste were collected and tested, in order to provide material properties for a mathematical stability analysis. Samples were also collected and tested of subgrade colluvium and bedrock for the same purpose. The stability analysis projected a minimum static slope safety factor of 1.64 for an overall facial slope of 2.5 H:1V, steeper then the requested configuration. At the request of the Division, West Elk Coal Company also completed an analysis of the potential stability affects upon the F-Seam, from the placement of a five million ton surcharge load upon the existing workings within the mine. The plan called for approximately the eastern half of the waste pile to be undermined. In completing this analysis, the operator assumed: 1. An ultimate configuration of the waste pile reaching elevation 6,880 feet above sea level. 2. No secondary extraction beneath the pile. 3. No barrier pillars, even though one is planned. 4. A continuous crack existing from the elevation of the F-Seam's floor to the ground surface at the top of the pile. Two separate conservative strengths were assumed for the floor clay beneath the F-Seam (angle of internal friction = 9°, cohesion = 1,350 lbs per square foot: angle of internal friction = 0°, cohesion = 4,320 lbs per square foot), resulting in safety factors greater than, 1.62. Further, the waste disposal pile would be constructed with granular underdrains, designed to prevent saturation or invasion of water into the waste pile. These five underdrains have been appropriately sized to ensure that the pile will not become saturated. West Elk Coal Company proposed to monitor both the ground water saturation beneath and within the pile, in order to ensure that the pile remained dry. The operator also agreed to install several survey monuments to monitor slope stability of the completed structure and adjoining areas.