Behind the steel and concrete: significant engineering projects maintain Halifax’s bridges
Maintaining complex infrastructure like the A. Murray MacKay and Angus L. Macdonald Bridges requires ongoing diligence and strategic planning. Each year, we undertake a wide range of engineering projects, both large and small, to address the bridges’ immediate needs and HHB’s long-term goals.
While some of the more visible projects, such as the replacement of the deck panels on the MacKay Bridge and resurfacing of the bikeway on the Macdonald Bridge are highlighted in other parts of this report, dozens of other significant initiatives undertaken in 2023-24 play a crucial role in ensuring the safety and reliability of the bridges.
Here are a few more projects of significance:
Angus L. Macdonald Dartmouth Cable Bent Steel and Paint Project
The paint and steel rehabilitation of the Dartmouth cable bent was a massive three-year, $15-million undertaking and a critical milestone in the $75-million effort to ensure protective coatings extend the life of the Macdonald Bridge.
This project included crucial steel repairs, coating protection and bearing replacement at the tower where the bridge cables from the main tower are redirected – or bent – to the anchorage. It began with removing all the layers of paint that had been applied since the bridge’s initial construction. The bare steel was revealed, inspected, and repaired as needed. A zinc coating and two layers of paint were then applied to protect the structure. Special efforts were taken to minimize disruption to our neighbours, with full containment, special access and environment control measures maintained.
At completion, staff were invited to climb the cable bent to get a first-hand look at this vital project.
Angus L. Macdonald Approach Spans Concrete Rehabilitation – Dartmouth Abutment
The original concrete foundations of the Angus L. Macdonald Bridge were built in the 1950s, when concrete generally was designed for a 50-year service life. A multi-year construction program that includes removal and replacement of outer concrete and reinforcing steel on the Halifax and Dartmouth abutments began in the summer of 2023 with work on the Dartmouth abutment. That work is ongoing, with construction set to begin at the Halifax abutment in the fall of 2024. Construction costs for the two abutment projects will be about $2 million.
Angus L. Macdonald Approach Spans Bearing Replacements
The approach spans bearings are designed to allow movement between the foundations and the bridge itself, but several of the bearings, which also date back to the original construction of the bridge, were no longer working. The removal and replacement of bearing assemblies in two areas of the bridge was done during closures in April and October 2023 and is part of a multi-year project. Construction costs totaled $500,000.
Angus L. Macdonald Approach Spans Resurfacing
The approach span decks were replaced in 1999 as part of the Third Lane Project, and the wearing surface was fully resurfaced in 2009. Beginning in fall 2022 and into the summer of 2023, the spans were resurfaced during four weekend closures. The $3.7-million project involved the removal and replacement of the wearing surface, including waterproof membranes, and replacement of two expansion joints.
A. Murray MacKay Main Cable Inspections
Suspension bridges like ours are unique structures with cables to carry the weight of the decks and traffic to the towers that support them. As part of the ongoing evaluation of the main cables, cable inspections were done from July to November 2023, at a cost of $1.46 million. The project involved removing the cable wrapping system, including lead-bearing materials, inspecting the interior of the cable, and installing the new cable wrapping system.