September 22, 2006

Mining expertise used in Sudbury tunnel extension

PATRICIA WILLIAMS

staff writer

SUDBURY

It isn’t every day that miners are put to work blasting through rock to carve out a sewage collection tunnel. But subcontractors employed by McNally Construction Inc. of Hamilton are doing just that on a project that will add 6.5 kilometres to the city of greater Sudbury’s existing tunnel network.

The $31.1 million South End rock tunnel is being excavated some 75 feet below the surface. Construction is scheduled for completion in November 2008.

Principal subcontractor is Canadian Mining and Development Inc. of Azilda, Ont.

“Tunnelling adds an extra dimension,” says Robert Langlois, contract co-ordinator at Sudbury’s Dennis Consultants, the engineering firm overseeing the project. “Most sanitary sewers are built in open trenches and you’re using a backhoe to lay pipe.

“What we’re doing here is drilling and blasting a conduit through rock.”

McNALLY CONSTRUCTION INC.

Miners loading round for a blast at tunnel ramp portal.

An environmental assessment report completed for the city in 2001 by the consulting firm determined that construction of a rock tunnel was the most cost-effective option to provide additional, long-term sanitary sewage capacity in the south end.

Without this expansion, the city would have been forced to freeze all new development in the area.

General contractor McNally began preparing the site near the intersection of Regent Street and Old Burwash Road last August. The entire rock tunnel is being constructed from a single staging area.

Contractors are accessing underground work sites by a ramp system that descends from the surface to a final depth of approximately 75 feet.

Excavated material is being transported to a property north of the Petro-Pass facility. This material will be used for a future road construction project.

“One of the tunnel’s selling points was the fact that it is down out of the way,” Langlois said. “You don’t see it. You hear blasts now and then, but you’re not interfering with traffic.”

McNally project manager Dan McNally, whose firm carries out tunnelling projects across North America, said this type of work usually is done with tunnel-boring machines.

While that option was considered, geological reports indicated that the rock was too hard to accommodate that approach. Thus, a decision was made to use the drill and blast method.

McNALLY CONSTRUCTION INC.

A miner rock bolting in Sudbury South End Tunnel access ramp.

“Finding the right people to do the work was challenging,” McNally said. “The construction industry doesn’t employ drill-blast type people. We had to find those people from the mining industry.”

On the engineering side, Langlois said innovative technology has been incorporated to control odours in the tunnel.

The project is funded by the city and the province under the infrastructure renewal initiative.

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