A year into a $12 million rehabilitation program of the 62-year-old Canso Causeway swing bridge in Nova Scotia has progressed on schedule.
There are still challenges ahead on the busy Trans-Canada Highway link between Nova Scotia’s mainland and Cape Breton Island and meeting deadlines is critical because the bridge affects marine, highway and rail traffic, say project stakeholders.
Rehabilitation work currently underway on the superstructure, for example, must be completed by May because that is when the marine waterway below opens to shipping, says Andrew MacPherson, project engineer, Nova Scotia Transportation Infrastructure and Renewal.
A temporary two-lane 50-metre-long steel modular panel bridge installed last fall on temporary foundations must be removed as well by spring. That crossing has been the detour route for Trans-Canada Highway and pedestrian traffic during construction on the swing bridge.
The Canso Causeway swing bridge is a 90-metre-long steel through-truss design. It has two vehicular lanes and tracks for rail traffic. It swings open for shipping vessels passing through the Canso Canal.
Work on the bridge has included repairs to primary structural steel components and replacement of corroding secondary steel members, such as bracing and lattices, says MacPherson.
The bridge’s superstructure is currently being sandblasted in preparation for a new protective three-coat system comprised of an inorganic zinc primer, an aluminum epoxy mastic midcoat and a polyurethane topcoat, he points out.
The new coating system replaces one installed in the 1990s.
MacPherson says that the aging coating had been battered over the years by heavy winds "that pound the causeway." Salt and rain had also taken their toll on the coatings.
Allsteel Coatings Ltd. of Port Hawkesbury, N.S., is the prime contractor for the rehabilitation project. Its $9 million contract includes dismantling and removing the swing bridge’s operator’s cab perched above the deck of the old bridge.
A new three-storey replacement building with improved electronic controls and a computer system, plus an observation area for the bridge’s operator, was recently completed on land adjacent to the bridge.
MacPherson says that in tandem with the rehabilitation, another tender was issued to Dexter Construction for erosion protection of various portions of the causeway. It involved "a bulking up of the armour stone" where there has been "some minor slope failures and erosion."
The contract included barging about 2,000 tonnes of stone to various undermined areas and placing those stones below water.
The Canso Causeway swing bridge rehabilitation program is scheduled for completion in October.