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Section - 2.05.3 Where: phi =Internal friction angle . cohesion =Cohesion of material gamma =Unit weight of material The material characteristics from all three mines were used to calculate a safety factor for the East Yard Coal Refuse Facility. The factor of safety against failure for final design conditions for the East Coal Refuse Facility was determined utilizing acomputer-assisted limit equilibrium method of slices. The program used to analyze the stability of the East Yard Coal Refuse Facility (GEOPRO) utilizes the Bishop's method of analysis. The GEOPRO program was developed by Dr. N. F. Nash, under the company name DataSurge. The most conservative factor of safety (lowest) was generated using the material characteristics from the $lue Ribbon Mine site. These materials came from the neazby West Elk Mine and are physically similaz to those generated by the Sanborn. Creek Mine having come from roof falls and mine development in xhe Sanborn Creek and Bear Mines. The stability analyses indicated a minimum static safety factor for the East Yard Coal Refuse Facility slopes of 7.6. The East Yard Coal Refuse Facility area will be reclaimed by grading bench surfaces and outslopes to a stable configuration with rounded edges blending with the surrounding terrain. The regraded surfaces will be capped with a mittimum of 4 feet of suitable soil materials from the Elk Creek soil stockpile and/or other sources and revegetated. West Valley Coal Refuse Facility -The West Valley Coal Refuse site, located in the first ephemeral drainage to the west of the existing Elk Creek surface facilities, was selected from several potential sites evaluated because existing slopes are flatter than several of the other prospective disposal azeas, upslope drainage can be readily divened, the area provides sufficient disposal capacity for currently anticipated future mining operations, and the area is readily accessible from the existing mine facilities. • The West Valley Refuse Facility will provide additional disposal capacity for approximately 120,000 cubic J>ards of refuse material. The facility will be accessed from the West Valley Haul Road. The refuse materials to be placed in the West Valley Coal Refuse Facility will be essentially the same as those now going to the East Yard Coal Refuse Facility since they will come from the same or similar sources. The stability of the West Valley Coa] Refuse Facility was analyzed using essentially the same material characteristics as used in analyzing the East Yard Coal Refuse Facility and the program PCSTABL (Version 6H, Purdue University, ]988) which utilizes the Modified Bishop Method. The stability analyses indicated a minimum static safety factor for the West Valley Coal Refuse Facility slopes of 2.7. The West Valley Coal Refuse Facility was designed and it's stability evaluated by Westec as documented by the design report included in Exhibit 2.05-E4, Mine Development Rock/Coal Refuse Facility Design. Designs were reviewed and modified as appropriate to address DMG concerns by Balaz & Associates. Soil materials from the West Valley Coal Refuse Facility have been stockpiled in the expanded Elk Creek soil stockpile for future reclamation use. Surface drainage from the refuse pile, stripped areas, and adjacent areas as well as any infiltration intercepted by the underdrain will be routed to Sedimentation Pond C to allow settlement of suspended solids prior to discharge to the North Fork of the Gunnison River. At any point in time, the area stripped for subsequent refuse placement and related activities is not anticipated to exceed approximately one-third of the overall refuse pile footprint. The progress and timing of refuse pile construction will be wholly dependent on the amount of coal mine refuse generated by ongoing mining operations. This amount can vary significantly dependent on mining conditions but is projected to range from approximately 3,000 to G,000 cubic Yards annually. The West Valley Coa] Refuse Facility area will be reclaimed in a manner similar to that described for the East Yard Coal Refuse Facility. J TR-43 2.05-47a Revised August 2003