PERMFILE70607 - Laserfiche WebLink

Home Browse Search

establish stable slopes at a maximum grade of 3:1 and create a bond reclamation configuration, • which provides for effective drainage. Recontouring volumes were developed by first establishing lateral and longitudinal cross-sections depicting the disturbance azea configuration for the maximum disturbance scenario. Recontouring lines were then drawn on each cross-section to meet the slope design criteria and to balance cut and fill volumes. These recontouring lines form the framework for the topographic surface shown on the Bond Calculation Regraded Topography Map -South, Map 36. Cut and fill volumes for recontouring were calculated by comparing the maximum disturbance topography to the proposed recontoured topography using Softdesk, and AutoCAD computer software programs. An earthmoving swell factor of 25 percent was used to convert from bank cubic yazds (BCY) to loose cubic yazds (LCY). This factor represents an average based on 20 to 22 percent swell for truck/shovel and dragline spoils and a 30 percent swell associated with cast blasting. Documentation for calculated recontouring volumes is presented in Appendix A, Volume Documentation. Given relatively long, deep pit configurations, cast blasting of final benches and highwalls was assumed as the initial step in recontouring pit areas. It was assumed that drilling for cast blasting would be accomplished with overburden drills and that a contracted down-hole service would be utilized for explosive loading and blasting operations. Areas and total overburden volumes which could be blasted were determined using Softdesk, and AutoCAD computer softwaze programs, engineering judgment, and assuming a minimum overburden thickness of 40 feet for blasting areas. Once the azeas and volumes which could be blasted were determined, the amount of material which would be cast into or across the pit by blasting was calculated using the following formula (from -Productivity Improvements for Dragline Operations Using Controlled Blasting in a Single and Multiple Seam Opencast Coal Operation of Rietspruit, South Africa, refer to Appendix E, Other Documentation): Percent Material Moved = 0.17 + 0.57 XDepth/Width Assuming an average overburden or bench depth of 50 feet and average azea or bench width of 100 feet, approximately 46 percent of the material which could be drilled and blasted would be moved to its final placement location by cast blasting. Computer printouts containing calculations of total recontouring volumes, volumes of blasted material, and cast volumes aze presented in Appendix A, Volume Documentation. Once cast blasting operations have been completed, material movement distances for • recontouring will be limited, therefore, it was determined that a tracked dozer could be effectively utilized to complete most required final recontouring. Accordingly, average dozer push distances and operating grades were determined for each of the four disturbance azeas from the Bond s