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Analysis Methodology The calculations were performed using YSTABL O Version 5. This is an interactive slope stability analysis program designed to use either the Bishop or Janbu methods for calculating safety factors. The Bishop method was selected as being the most accurate application for this particulaz problem. The soil properties information was input along with slope geometry, loading information, water table information and definitions of limits for calculations. A total of 200 failure surfaces were generated for each of the three problems and the lowest safety factor selected. A minimum safety factor of 1.5 is assumed to be adequate to protect either of the structures. A slope failure had to actually pass through the structure to be deemed as a failure. If lesser slope failures such as minor sloughing at the face of the mining highwall occurred but did not touch the structure, they were judged to be insignificant. Analvsis Results The slope stability analysis resulted in factors of safety that were above the minimum of 1.5. In all cases, the lowest safety factor did not intercept structure structures. The minimum safety factor for the PSCo towers would result in a slope failure that would not touch the footings for the towers. Other slope failures that intercepted the towers had safety factors well above Z.0, which indicates the proposed 50 foot setback is adequate to protect the stability of the powerlines. The failure slope for the pit slopes adjacent to the Fulton Ditch also indicated that the minimum safety factor (1.67) would not intercept the actual ditch, but would intercept the toe ofthe ditch bank. Other slope failures that intercepted the ditch has lazger safety factors and indicated that the proposed 50 foot setback is adequate to protect the stability of the ditch The failure slope for the perimeter of the pit adjacent to public right-of--ways would not intercept structures outside the property line based on the assumptions used. The minimum setback along this perimeter would be 35 feet total with the %z:l highwall slopes being used. Vertical highwalls would be allowable with a ,;neater setback. Conclusiaus and Recommendations The following conclusions and recommendations aze offered from this analysis. The proposed mining operation can safely remove material with a setback of no less than 50 feet from the outside top bank of the Fulton Ditch. 2. The proposed mining operation can safely remove material with a setback of no less than 50 feet from the outside base of the powerline towers located in the PSCo easement that passes through the Cooley property. Each tower maybe mined leaving an island approximately 100 feet square. The mining can be done at a''/Z H: 1 V slope. The mined azea in the easement will then be backfilled to no less than historic ground elevation with overburden, clay material oc shale bedrock. All backfill would be replaced with a compaction standazd of at least 90% to prevent excessive settling. Page 3