Protecting vulnerable isthmus joining N.S. and N.B. will cost hundreds of millions: report

Raising or building new dikes will take a decade or more

Taryn Grant · CBC News ·

A newly completed study looking for ways to protect the vulnerable strip of land that connects mainland Nova Scotia to New Brunswick, and the rest of Canada, presents three options, all estimated to cost hundreds of millions of dollars.

Extreme weather and rising sea levels caused by climate change threaten to flood the Chignecto Isthmus by the year 2100.

Such an event could cut off a critical rail line and a stretch of the Trans-Canada Highway that allow for an estimated $35 billion in trade each year.

The isthmus is currently protected by dikes and aboiteaux first constructed by the Acadians hundreds of years ago. The new report on bolstering protection for the trade corridor, released Friday afternoon, says dikes are still the best solution.

The report recommends three options:

• Raising the existing dikes, at a cost of about $200.2 million.
• Building new dikes, at a cost of about $189.2 million.
• Raising the existing dikes and installing steel sheet pile walls at select locations, at a cost of about $300.8 million.

‘We definitely need our federal partners’

Cabinet ministers from Nova Scotia and New Brunswick told reporters Friday they are working with Ottawa to choose one of the three options, or a hybrid, and come to a cost-sharing agreement.

“What is required for this project is in the ballpark of what my whole capital budget is for a year,” said New Brunswick Minister of Transportation and Infrastructure Jill Green.

New Brunswick Transportation and Infrastructure Minister Jill Green. (CBC News/Jacques Poitras)

“It’s a big lift for New Brunswick and it’s a big lift for Nova Scotia, so we definitely need our federal partners.”

Kim Masland, Nova Scotia’s minister of public works, said a project of this size warrants a federal contribution, especially considering the possible consequences of water overtaking the isthmus.

“We understand the importance of this issue … and we will put in the time and the work and continue to work together in collaboration with the federal government to make sure we move this project forward on an expedited basis,” Masland said.

Ottawa paid for half the $700,000 study, which started in 2018, while Nova Scotia and New Brunswick split the other half evenly.

Kim Masland is the minister of public works for Nova Scotia. (Robert Short/CBC)

Officials told reporters at a technical briefing that each of the three options will require extensive co-ordination between all three levels of government, from the early stages of permits and environmental approvals all the way through construction.

In all three cases, the whole process could take more than a decade.

Towns should be protected

Parts of Sackville, N.B., and Amherst, N.S., are in the path of potential flooding on the isthmus, and politicians and residents have been calling for help with protection for years.

The key directive given to the engineers who wrote the report was not to protect those communities, but to protect critical infrastructure, namely the highway and rail lines. Each of the options presented, however, should protect both of those towns, officials said.

Amherst Mayor David Kogon said he’s satisfied with what’s on the table. Conservative estimates put dozens of people and businesses in his town in the flood zone, should seawater top the dikes.

“What pleased me the most today was to hear that the options under consideration … all are looking to not only protect the transportation corridor, but to protect the communities and the marsh farmland that’s so vitally important in our area,” Kogon said.

An aerial view of the Chignecto Isthmus. (Mike Dembeck)

The 10-year timeline is reasonable and realistic, according to Kogon.

“Truly, the prediction for flooding of the isthmus was that it might occur by 2100. That’s close to 80 years away, so to get this done in 10 years, I think is more than adequate.”

Disappointment

Some experts have said the best way to protect the isthmus is to breach the dikes, move them back and allow saltwater to return to some of the former marshland, and then encourage the development of a natural buffer with plants once tidal flow returns.

Using such a marshland buffer is not part of any of the options presented in the new report. Officials said it was not found to be a viable option. The omission was a disappointment to Danika Van Proosdij.

Danika Van Proosdij at a salt marsh near Windsor, N.S. The salt marsh formed after the construction of a causeway in 1970 and while it was not an intentional salt marsh restoration, she says it demonstrates the capacity of salt marshes to establish themselves in coastal environments. (Moira Donovan/CBC)

Van Proosdij, a professor at Saint Mary’s University in Halifax, researches this type of natural mitigation, and said evidence shows it’s effective in terms of cost, land protection, and environmental sustainability.

“There is absolutely a need for dike infrastructure, that is clear … however, creating situations where you can move a dike back strategically … provides a buffer that actually allows you to have the height of your dike to be lower.”

The dikes are currently about 8.5 metres tall, and the report says they need to be about 10.6 metres. It’s expected to be challenging to get the dikes that high, and is part of the reason for the 10-year timeline.

Van Proosdij said she’s not surprised marshland restoration was left out, “given the limited mandate and focus on protecting the critical infrastructure.”

She said she will continue to advocate for her approach to make its way into the final design.