Unique push back exercises, practiced at Iron Ore Company of Canada to optimize Humphrey pit designs ALI CHAMANARA*, KAZEM ORAEE**, DAVID R. G. MITCHELL*** * PhD candidate and Lecturer, School of Mining and Petroleum Engineering, University of Alberta **Professor, Department of Management, University of Stirling ***Senior mining advisor, Iron Ore Company of Canada Eighteenth International Symposium on Mine Planning and Equipment Selection November 17, 2009

Introduction Designs generated by computers are not always optimum. Designs generated by computers are not always optimum. A considerable increase in reserves was achieved by redesigning and rescheduling the Humphrey pit production program. A considerable increase in reserves was achieved by redesigning and rescheduling the Humphrey pit production program. The total stripping ratio was also was also reduced marginally. The total stripping ratio was also was also reduced marginally.

Location Labrador City and Wabush incorporated in 1961 and 1967 Population ~ 12,000 Sub-arctic climate dorwest.com/

Sept-Iles, Quebec Population 25,500 Deep-sea harbour accessible year-round One of the three largest Canadian ports for tonnage handled

History 1949-Incorporation 1949-Incorporation 1954-Completion of QNS&L Line 1954-Completion of QNS&L Line First Shefferville ore shipment First Shefferville ore shipment 1962-Commissioning of Carol Project 1962-Commissioning of Carol Project 1970-Expansion Program 1970-Expansion Program 1981-Closing of Sept-Iles beneficiation plants 1981-Closing of Sept-Iles beneficiation plants 1982-Closing if Schefferville operation 1982-Closing if Schefferville operation Major Milestones reached Major Milestones reached January, One Billion tonnes mined January, One Billion tonnes mined December M.A. Hanna contract terminated December M.A. Hanna contract terminated IOC becomes a stand-alone company IOC becomes a stand-alone company 1997-North Limited acquires controlling interest 1997-North Limited acquires controlling interest 1998-IOC becomes a 100% merchant supplier 1998-IOC becomes a 100% merchant supplier 2000-Rio Tinto Ltd acquires North Ltd 2000-Rio Tinto Ltd acquires North Ltd 2004-IOC celebrates transportation milestone 2004-IOC celebrates transportation milestone One-billionth tonne of iron ore shipped on QNS&L One-billionth tonne of iron ore shipped on QNS&L 2005-IOC celebrates its 50 th year 2005-IOC celebrates its 50 th year

Mine Evolution - Operating Areas

Carol Lake Mining Two active pits: Luce and Humphrey West/Main Two active pits: Luce and Humphrey West/Main Annual Production: ~60 Million Stripping Ratio ~0.58 t/t Annual Production: ~60 Million Stripping Ratio ~0.58 t/t Fe: 37-40% Fe: 37-40% Luce Low Weight Yield, Low Magnetite Humphrey High Weight Yield, High Magnetite

Product Manufacturing - Beneficiating Plants Annual Capacity: Concentrator (1) : million tonnes Pellet Plant (2) : 12.5 million tonnes ConcentratorPellet Plant

Final Pit Design Optimization 1- Honoring the boundaries of the NPV final pit shell 2- Development of the mining phases for; Operational efficiency Operational efficiency Connected operating areas Connected operating areas Ore/Waste options to maximize total output Ore/Waste options to maximize total output Less road/ramp building over time Less road/ramp building over time Phases which provide scheduling flexibility Phases which provide scheduling flexibility The ability to schedule with few restrictive rules and ascertain that the path outlined is minable The ability to schedule with few restrictive rules and ascertain that the path outlined is minable

Strategic Plan Value (In house planning) Provide the managers with alternatives; Provide the managers with alternatives; Benefits/consequences Benefits/consequences Provide operational people with awareness of the pit development path Provide operational people with awareness of the pit development path Better judgment for work priorities Better judgment for work priorities Elimination of rework Elimination of rework

Humphrey Final Pit Designs

Humphrey Geology Cross Section

Humphrey Original & New Final Pit

East Wall Push Backs

Spiral Push Back

Humphrey Final Pit

Conclusion More than 15 Million tonne increase in reserves More than 15 Million tonne increase in reserves Stripping ratio decreased by 0.01 t/t Stripping ratio decreased by 0.01 t/t Higher scheduling flexibility Higher scheduling flexibility More effective blending More effective blending Increase in iron ore concentrate due to high iron content in Humphrey reserves Increase in iron ore concentrate due to high iron content in Humphrey reserves Increasing the operational efficiency and hence creating better opportunities to mine Sherwood Pond reserves Increasing the operational efficiency and hence creating better opportunities to mine Sherwood Pond reserves

Acknowledgment The authors would like to thank the mine general manger, Mr. Matt Simpson, the mine chief engineer, Mr. Andrew Knight, and the senior geologist, Mark Blake, at Iron Ore Company of Canada for their kind supports.