Building a bridge over a sensitive stream is always delicate business. It’s particularly difficult when the bridge needs to go through a deep valley and over a cold-water trout stream (in this case, Silver Creek), that also happens to be the spawning ground for salmon from Lake Ontario. This is the dilemma for the town of Halton Hills, Ontario, Canada, which is in the process of building a bridge to link a newly developed residential area to Highway 401 and Highway 7. Because the bridge is in the bottom of a deep valley, a cellular-confinement system (CCS), manufactured by Presto Products Co., Appleton, Wis., was used to stabilize the steep slopes. The town’s construction plans, however, have to satisfy more than the residents.
“That stream means we’ve got the Federal Fisheries Act, the Ministry of the Environment and Engineering and the Credit Valley Conservation Authority involved,” says Doug Inouye, Halton Hill’s manager of construction services. “It was important to stabilize the slopes and restore them to as natural a state as possible.”
“We’re building at a slope of 1.5H to 1 V, a practice against my better judgment,” says the project’s engineer Lyle Malcolm, McCormick Rankin and Associates, Mississauga, Ontario, Canada. “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.”