Citing an increased risk of flooding on the Don River, Enbridge has decided to move a critical section of natural gas pipeline underground to keep it safe from damage.

The pipeline, which currently runs over the river on a narrow bridge near Eastern Avenue, will be removed and replaced with a new 300-metre stretch under the river bed.

The pipeline services tens of thousands of customers in the city's core, including a power generating centre and numerous institutional and government buildings.

"Data suggests that extreme weather events are occurring more frequently than expected ... [which] pose a particular challenge to the operation of municipal, provincial and utility infrastructure," wrote Enbridge in its project application to the Ontario Energy Board.

Beth Williston, associate director of planning and permitting at the Toronto and Region Conservation Authority (TRCA), puts it more bluntly.

"These flood flows are becoming more frequent and with greater intensity with climate change. We definitely don't think that's the best place to have a gas line," she told CBC Toronto.

Construction begins this spring

Following an environmental assessment, the TRCA gave Enbridge the green light to bury the pipeline instead, keeping it safe from flood events on the Don that could damage it or take out the bridge it's attached to, which was built in 1929.

"It was determined that the best place environmentally and from a construction standpoint was to drill through the bedrock underneath the floodplain of the Don," said Williston.

"If the bridge is damaged, so is the pipeline, so we are trying to make sure that the pipeline remains intact and safe," Enbridge spokesperson Tanya Bruckmueller told CBC Toronto.

The trees in a lot near Eastern Avenue have been removed to make space for the Enbridge construction project, which will run from one side of the river to the other. (CBC News)

A grove of trees near Broadview and Eastern avenues has already been cut down as crews prepare to begin construction on the new underground section.

The trees will be replanted after the work is finished.

"Once the project is complete, we've provided the money back to the city [which] will make the decision on where to plant the trees," said Bruckmueller.

The new underground pipeline could be complete as early as November, she said.

City-wide shift towards resilience planning

Elliott Cappell, the chief resilience officer for the City of Toronto, says projects like this one are part of the growing move to mitigate the effects of climate change and protect the city's assets.

"Toronto's going to get hotter, wetter and wilder, and although we are coming from a really great starting point, there's a lot of work to do in terms of retrofitting our assets and changing the way we think about and plan infrastructure," he told CBC Toronto.

It's a shift Cappell says he's seeing in the private sector and public sector alike.

"It's an issue that affects us all and cuts across what you see as the normal sides of the debate around climate change," he said.

Though the new pipeline is a mitigation measure, Williston says it still represents a win for the environment.

"We're looking at a net gain environmentally," she said. "Not only because we will not have an impacted pipeline with potential flood flows, but we will also have a net gain with the trees being re-established in other areas — both of which are positive contributors to creating a more resilient city," she said.

"We're not going to lessen climate change by any means with this project, but we are working towards mitigation efforts that will help us have more city resiliency in our infrastructure."