Partial Pit Backfill Alternative

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A presentation on Partial Pit Backfill Alternative associated with the Rosemont Copper Project Operations. This presentation was given by Rosemont Copper to the Forest Service, the Cooperating Agencies, and their contractors during a meeting in January 2010.

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Partial Pit Backfill Alternative

  1. 1. Partial Backfill Alternative January 21, 2010Cooperator’s Meeting Presentation
  2. 2. Partial Backfill AlternativeConsiderations•  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. 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
  4. 4. Pit Lake Development
  5. 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. 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. 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. 8. Backfill andExcavation 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. 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 419This information was used to determine the appropriatehaulage fleet for this activity matched to one shovel.
  10. 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.

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