March 26, 2010

WILLIAM CONWAY/PROGRESS PHOTOGRAPHY

Two major watermain installations in Peel Region by McNally Construction are nearing completion.

FEATURE | Sewer and Watermain

Ontario’s Peel Region feedermain is nearing completion

Two projects at either end of Peel nearly done

DAN O’REILLY

correspondent

While there are still a few months of work left, the end is almost in sight for McNally Construction on two major operations underway in opposite ends of Peel Region.

Using a 96-inch Lovat TBM soft ground machine, it is installing a 2,100-metre-long sewer and an accompanying 1,000-metre-long 600-mm watermain along Dixie Road in north Brampton. The lines cross for a short stretch over Mayfield Road into the Town of Caledon. Work started early last fall.

The tunneling is approximately 50 per cent complete and the project is scheduled for completion in October, says project manager Armenio Martins.

Meanwhile, in south Mississauga, the contractor is completing the final elements of what has turned out to a much more rigorous and complicated undertaking.

The Hamilton-based firm is one of three contractors responsible for three different sections of the overall $90-million six-kilometre Herridge feedermain project.

Once completed, the feedermain will deliver water from the Lorne Park Water Treatment Plant to the Herridge Reservoir and Pumping Station to help meet future growth demands in Mississauga and Brampton.

McNally is responsible for the tunnelled installation of 1.8 kilometres of concrete pressure pipe from Lakeshore Road to the Queen Elizabeth Way. Site work started in August 2008 and for the most part the project has been a straight-forwarded tunneling and pipe installation operation, says Martins.

With a Robbins tunnel boring machine, which is designed to dig rock, and two shifts of nine men per shift, the contractor was able to excavate about 100 to 140 feet of the shale per day. That was followed by the installation of approximately 300 pieces of 20-foot-long concrete, 2.1-metre-diameter pressure pipe supplied by Munro Concrete Products Ltd.

With the exception of a steel channel with wooden support members for the crown, the pipe was simply placed into the shaft. “Because the area is mostly shale we did not feel the need for slagging support.”

In March 2009, however, the contractor faced a major setback when those ground conditions changed suddenly. “The shale changed to weathered shale mixed with clay and water.”

With limited geotechnical information for that particular zone, McNally decided to drill boreholes to determine the extent of those changed conditions. It was during that process that gasoline deposits were also discovered, said Martins. The Region of Peel retained the services of The Cannington Group to remediate the area and a dewatering was also conducted by Aquatech.

As the remedial work was being carried out, McNally designed and then installed an approximately 25-metre-long arch plate support system to allow tunnelling to continue through the wet section.

But the whole remediation and design process took six months and during that period most of the work crews had to be reassigned elsewhere, he says.

Once that was completed, however, the project resumed without any major hurdles. The mining was completed last November and by the end of February the entire pipe was in place.

With grouting and the construction of two valve chambers, Martins expects the project to take another five months to wrap up.

The feedermain’s two other phases are in different stages of completion, says Peel Region project manager Jeff Hennings. Phase one is the tunnel installation of 2.7 kilometres of pipe from the Lorne Park plant to Lakeshore Road and then to Southdown Road by C & M McNally Engineering Corp. “They are about 95 per finished.”

A third phase of primarily open cut construction is being overseen by the ConDrain Group.

This phase also includes a small tunnel operation of about 400 metres under the Queen Elizabeth Way by subcontractor Technicore Underground Inc.

That work should be completed within a few weeks, says Hennings.

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