Partial Pit Backfill Alternative
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The document discusses the partial backfill alternative for a mining project, focusing on environmental compliance, minimizing impacts, and logistical considerations for backfilling waste rock. It outlines the estimated materials and time required for backfilling, as well as productivity metrics related to excavation and haulage. Key details include volume estimates, backfill elevations, and operational parameters for material transport.
Partial Pit Backfill Alternative
- 1. Partial Backfill Alternative January 21, 2010 Cooperator’s Meeting Presentation
- 2. Partial Backfill Alternative Considerations • Be responsive to an Issue • Minimize water that collects in the pit • Return waste rock to the pit • Minimize resources that are used in backfilling • Minimize air impacts
- 3. Partial Backfill Alternative Environmental Considerations • Compliance with all applicable regulations including ADEQ BADCT and air regulations • Maintain a Hydraulic Sink • Geochemical considerations with the addition of a mix of finer grained materials • Stormwater controls during backfill • Effect on concurrent reclamation and on reclamation planning
- 5. Hydrogeologic Study Results Pit Lake Pit Lake Depth Period Elevation (feet) (ft amsl) Mine Closure (None) 0 Closure + 20 years 3,591 541 Closure + 50 years 3,751 701 Closure + 100 years 3,869 819 • Backfill elevation – 3825 ft amsl (est.) • Elevation was estimated to maintain sink (modeling to confirm elevation estimation with operational adjustments as necessary)
- 6. Other Considerations • Heap Leach remains undisturbed • Haulage fleet used will be consistent in size to current fleet • Loading equipment (shovel used will be consistent with current loading equipment) • Waste rock density is 11.95 ft3/ton • Swell factor for the rock is 1.3
- 7. Other Considerations • Amount of material necessary for backfill is 90 million tons (46 million cubic yards) • Allowance of 5% added for construction of ramps for downhill haulage • Total material rehandled 94 million tons • 36-months required to complete backfill • Hauls will incorporate 3 switchbacks at -10% grade at a maximum 13 mph
- 8. Backfill and Excavation Area • Excavation on 50 foot benches • Start elevation approx 5429 ft amsl • Final elevation 5200 ft amsl • Dumped into pit from 3825 ft elevation
- 9. Productivity by Bench Bench Tonnage Cumula+ve Haulage Eleva+on (x 1,000) Tonnage Produc+on (. amsl) (x 1,000) (tons/hour) 5420 8,938 8,938 379 5400 18,435 27,373 387 5350 18,689 46,062 395 5300 16,277 62,338 403 5250 12,977 75,315 411 5200 8,720 84,036 419 This information was used to determine the appropriate haulage fleet for this activity matched to one shovel.
- 10. Required Haulage Hours and Units Rehandle CAT 793C Truck Fleet Post-‐Mining Tons Year Opera+ng (x 1,000) Units Hours 1 28,774 74,740 16 2 28,853 72,439 16 3 26,409 64,021 15 Total 84,036 211,201 16 Modeling indicates that 16 trucks will be required in the first 19 months of the project and 15 for the remainder.