Options explored for replacing versus rehabilitating MacKay Bridge

Halifax's new bridge could one day be even newer.

Earlier this week, Halifax Harbour Bridges (HHB) announced it had submitted an application to the Nova Scotia Utility and Review Board requesting its first fare hike in 10 years.

If successful, the cash toll would go up 25 cents from $1 to $1.25 and MACPASS users would pay $1 instead of 80 cents.

HHB said the extra funds are needed for capital projects over the next decade, which are expected to cost more than $280 million. One of those is the study and preliminary design for the replacement of the MacKay Bridge.

Although still structurally safe, the 51-year-old suspension bridge is nearing the end of its life span.

HHB CEO Steve Snider said right now the orthotropic deck plate on the MacKay is only 9.5 mm thick, which doesn't meet the current minimum code requirement of 14 mm.

“My understanding is steel structures that have continuous loadings on them will experience fatigue and the MacKay Bridge fatigue life for the steel deck, it has a projected finish date,” he told NEWS 95.7 fill-in host Jordi Morgan.

“We will be maintaining that deck, but it gets to the point where it's no longer reasonable to maintain it … so the question is, do we do something like we did on the Macdonald Bridge? Do we replace that deck or do we consider replacing the entire bridge?”

A feasibility study by COWI North America Ltd. has explored nine different plans for the MacKay's future.

Three involve rehabilitating the current bridge, which would extend its life for another 75 years. Options include keeping the design as is, adding active transportation (AT) lanes for pedestrians and cyclists, and twinning it with a second span, which would allow it to have AT lanes and be expanded to six vehicle lanes, so one Halifax bound lane and one Dartmouth bound lane could be reserved for emergency vehicles and buses.

The other six proposals involved replacing it with a new bridge that would last 100 years. The options considered the possibility of active transportation lanes, four versus six lanes, two different span lengths and suspension versus cable-stayed designed.

According to the report by COWI, if they go with rehabilitation, a thicker orthotropic deck plate that meets current codes wouldn't be as flexible, and because of that, other interconnected components would also need to be replaced. It's likely those new components would be heavier and require spans to be reinforced and cables to be strengthened.

The plan to rehabilitate the bridge without adding any additional features comes in at an expected $840 million.

With the exception of the twinned option (which is estimated to cost $1.35 billion), it's expected rehabilitation would also result in the bridge being shut down for long periods of time, and those closures would be “likely more extensive” than what we experienced during the Big Lift project on the Macdonald Bridge.

“[COWI's] recommendation was that it's best value for Halifax Harbour Bridges, and thus for those of us who pay the tolls, to replace the bridge rather than try to rehabilitate it,” Snider explained.

The consultants' preferred option is a six lane cable-stayed design that has two active transportation lanes. It comes with an estimated price tag of $1.05 billion. 

They recommend building the new span just north of the MacKay, which would require the acquisition of property and the relocation of the current Canadian Food Inspection Agency building in Dartmouth. However, Snider said we're just in the initial stages of this discussion and there's “a lot more thinking that needs to be done.”

“We'll be heavily engaged with the province, with the city and with the local community to examine the plan forward,” he said.

“As you can imagine this is a very, very significant project with a long timeline,” Snider added. “The report has identified that under normal circumstances it takes eight to ten years from the beginning of the planning to the completion of the project. We've got almost 20 years in front of us before the date we've identified that the bridge should be replaced.