February 26, 2010

DAN O’REILLY

An Aecon crew is building an H-pile wall with soil nail anchors to stabilize the north embankment of the Forks of the Credit Road so the road can be relocated three metres.

FEATURE | Roadbuilding

Challenging repairs on seven kilometre stretch of Forks of the Credit Road in Caledon, Ontario

DAN O’REILLY

correspondent

The challenges of reconstructing and stabilizing the Forks of the Credit Road in Caledon are almost as awe-inspiring as the scenery.

Winding through the Caledon Hills from Highway 10 to Mississauga road beside the Credit River, the seven-kilometre road is considered by many to be one of the most picturesque in southern Ontario. For such a short road, it is one with a number of complex — and potentially dangerous — trouble spots, says Peel Region project manager John Hasselbacher.

One section was threatening to slide into the Credit River, another, overlooking a deep valley, needed reinforcement and a third area was and is being eroded by a small, but significant watercourse, he said.

“The slippage wasn’t happening right away and wouldn’t be catastrophic. But then again it might,” says Hasselbacher, in explaining the need for a $4.9 million selective reconstruction last August. It was scheduled for completion by the end of March so the region can qualify for federal infrastructure stimulus funding. Aecon Construction and Materials Ltd. is the general contractor and Trow Associates is the consultant.

Originally planned as straightforward resurfacing, the project expanded when two sections of the road were deemed unstable, Hasselbacher said.

The worst of these sections was approximately 200 metres long. Immediately adjacent the Credit River, it formed part of the river embankment in spots. “The problem was that the road was slipping into the river.”

A second Aecon crew is installing a steel sheet pile wall with vertical H-piles to retain the road, which is right at the edge of the ravine.

A two-fold approach to stabilizing the road and river embankment was put into place. First, Aecon crews built a buttress wall along the river edge and then, reconstructed the road in layers using a reinforced soil slope.

This section was particularly challenging because of the environmentally sensitive nature of the river. An extensive consultation with the Ministry of Natural Resources on measures to protect endangered species was required. There was also significant consultation with the Credit Valley Conservation Authority and the Niagara Escarpment Commission, says Hasselbacher.

Elaborate methods, such as installation of a Jersey barrier wall, were undertaken to ensure no dirt or debris infiltrated the river, he says.

All of the in-water work had to be conducted from July to September, so as not to interfere with the fish spawning.

“But we did get an exemption until Oct. 15 for the upper embankment work,” says Aecon project manager Mark Arbeau.

Aecon’s crews are now at the second site, which is located on what is known as the “hairpin turn,” a large and sharp curve in the road rising to the top of the Niagara Escarpment.

This second site is comprised of two segments. At one of those areas workers are installing a steel sheet pile wall with vertical H-piles to retain the road, which is at the edge of the ravine.

“You could actually see the road slipping and it would have collapsed over time,” says Hasselbacher.

“The wall reinforces the existing roadway and the fill below it, plus increases the safety of the slope to within acceptable limits.”

The H-piles support the sheet walls, which couldn’t be drilled down to the originally planned depth because they were blocked by unanticipated large rocks and boulders.

“We had to modify the design.”

Around a bend and higher up the escarpment, another Aecon crew is installing an H-pile wall with soil nail anchors to stabilize the north embankment so the road can be relocated three metres.

The complexity is a direct result of the design solution to eliminate erosion caused by the watercourse on the south side.

“We can’t interfere with the watercourse, so we’re moving the road, he says.

A concrete facing simulating the area’s limestone topography will be eventually added to the wall as part of the post-construction landscaping, he says.

For most of the project duration the road has been closed and that necessitated a public relations initiative to keep residents informed, says Hasselbacher.

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