Project Profile: Geoweb System Used to Protect Salmon Stream

Jan. 1, 2000

Building a bridge over a sensitive stream is alwaysdelicate business. That’s why McCormick Rankin & Associates specified Presto’s large-cell, tendoned Geoweb Cellular Confinement System for a bridge-approach embankment in the municipality of Halton, ON. This system will provide vegetated protection on the 1.5:1 slope and is the first large-scale application of its kind in Toronto.

Mountainview Road is a major arterial linking a newly developed residential area to Highway 401 and Highway 7. The project encompasses an area from 0.2 mi. south of #10 Side Road to 0.1 mi. north of Summit Lane/Eden Place in the town of Halton Hills (Georgetown).

“We’re building a bridge through a very deep valley,” explains Doug Inouye of the Municipality of Halton. “It was important to stabilize the slopes and restore them to as natural a state as possible.”

The Geoweb large-cell, tendoned confinement system provides vegetated protection on this 1.5:1 slope.

Complicating this process is the fact that the valley boasts a cold-water stream, Silver Creek, which holds trout and is the spawning ground for salmon from Lake Ontario. “The stream means we’ve got the Federal Fisheries Act, the Ministry of theEnvironment and Engineering, and the Credit Valley Conservation Authority involved,” Inouye points out.

“We’ve had a good relationship with the Credit Valley Conservation Authority,” notes Lyle Malcolm of McCormick Rankin & Associates. “We’re mindful of the fact that Silver Creek is a tributary of the Credit River, which has a significant salmon run from Lake Ontario. All siltation control works have been quite satisfactory to the Conservation Authority to date. We’re building at a slope of one and a half horizontal to one vertical, a practice against my better judgment. That’s the reason for using the Geoweb material-we’re trying to minimize the footprint on the valley. It’s one of the most memorable projects I can recall-not because of the size of the bridge but because of the sophistication of the approach fills.”

Mass plantings were used for additional stabilization.

McCormick Rankin wanted a permanent solution and chose the Geoweb system as the primary reinforcement. It did not want to rely solely on typical bioengineering to hold the slope. Further, because of the timing of this project, bioengineering efforts typically done in the spring and fall were not possible. Instead, mass plantings would be used for additional stabilization. The large-cell system allows for planting of shrubs and trees within the cells.

“We’re glad we had the opportunity to demonstrate this system in the Toronto marketplace. Because Presto offers a tendon system, it was the only cost-effective product that was appropriate for the severe slopes on this project. The tendoned Geoweb system provides the structural mechanism to secure the system from sliding on steeper than typical slopes,” says Eric Jashewski of Armtec Construction Products, representative for Presto Products.