May 2010

Making the grade

The challenge of smooth roads and more loads at Canadian operations

By Heather Ednie

If the orebody is the heart of a mining operation, the haul roads are its arteries. Keep them in good shape, and equipment will move efficiently. Allow them to deteriorate, and the well-being of the entire operation can be at risk.

The haul road programs of most open pit operations in Canada share three common considerations: safety, environmental management and equipment management. Good roads are safer and can contribute to lower vehicle emissions, better water management and longer equipment life spans.

Adapting the terrain

Each year, four to five kilometres of new haul roads are built at Syncrude Canada’s Mildred Lake and Aurora mines. These roads are designed to last the duration of the mine life and their construction is a multi-staged process involving collaboration between different company teams.

At the outset, the long-range planners design the layout of the road, accounting for expected volumes of traffic and the timing and scheduling of production activities. Once the design is in place, it is up to the short-range planning group to incorporate its requirements into the overall operation plans and to secure the timely supply of the requisite materials. Finally, the job of having the roads built goes to the haul road construction group, which oversees the contractors. As one might expect, the actual road construction process entails some very intricate steps.

Crowned subgrades need to be constructed first, providing a solid foundation for the road. The crown prevents the water that seeps through the granular layer immediately above it from permeating the subgrade and helps drain it off the road. Operations at Syncrude don’t stop for the weather, so the roads are built to handle it.

“The subgrades are the most important part,” says Rod Walsh, a field supervisor who has been with Syncrude for 23 years. “You can have the best granulars, but the road will break down if it doesn’t have a solid subgrade.”

Due to differences in the materials available at the two mines, their road designs vary. At Mildred Lake, Cretaceous-era marine clays, packed to 101 per cent of proctor, are used as a subgrade material. At Aurora, these marine clays are not available, so lean oil sand is used to build the subgrade, which is not as effective. To balance it out, alterations are made to the rest of the road design.

Once Syncrude builds and approves the subgrade, local contractors construct the roads. Approximately $8 to $10 million — $2 million a kilometre — is spent on road construction annually at both mines.

Pit-run gravel and sands found on Syncrude’s own lease are used to construct the base. However, Ken Bell, technical leader, Mildred Lake, foresees a shortage of this material in the future. “So we need to be innovative in our approach to smart granular management,” he says.

Granular usage can be reduced by “flipping” or reclaiming materials from roads no longer in use. This road recycling offers several advantages. Less granular needs to come out of the quarry, water management becomes easier, material haul distances are shortened and royalties need not be paid for the recycled materials. Once the road is built and tested, it is signed off to the operations people, who assume responsibility for its maintenance.

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