Edmonton

Fort McMurray's flood mitigation berm system seriously flawed, report says

Fort McMurray's multi-million-dollar berm system, the heart of the community's flood mitigation efforts, is incomplete and seriously flawed, concludes a report by an independent engineering company.

'A comprehensive flood-protection system was not in place at the time of the 2020 river-breakup flood'

Jason Vanderzwaag, manager of Associated Engineering, pointed to this photo, noting there was water on both sides of the berm in Fort McMurray, despite the barrier having not been breached. (McMurray Aviation )

Fort McMurray's multi-million-dollar berm system, the heart of the community's flood mitigation efforts, is incomplete and seriously flawed, concludes a report by an independent engineering company.

Some sections of the flood berm are built to withstand a once-in-40-year flood, while others protect against a once-in-100-year flood level, the report says. 

Also, culverts and vents run throughout the berm allowing water to find pathways through the barrier, eventually flooding the sewer system and backup into homes.

"The house itself may not be flooded at the surface, but because the sanitary sewer may be backed up or is backed up, the water was able to come back up that sanitary sewer line into every house," Jason Vanderzwaag, manager of Associated Engineering, told municipal council Tuesday night, during a marathon, 11-hour special meeting. 

The inconsistent and porous berm allowed water to gush through the system of berms from multiple angles, the report said.

Water passed over parts of the berm that were too low to withstand a once-in-100-year flood, entering the sewer system, causing backups into people's basements, it said.

In short, "a comprehensive flood-protection system was not in place at the time of the 2020 river-breakup flood," Vanderzwaag said.

Associated Engineering included a diagram of how water bypassed the berm system. Water travelled through underground pathways and equalized itself despite the berm. (Associated Engineering)

"Instead, what there was, was a series of different infrastructure elements built to different standards … these elements weren't constructed to act as a single comprehensive system." 

The report quashed rumours that Fort McMurray's flap gates, a barrier that lets storm water enter the river but closes to stop river water from flowing backwards, failed, although the gates were compromised.

The report found the water treatment plant had multiple faulty mechanisms, leading to the almost three-month boil water advisory in town. 

The sluice gate, which moves up and down to control water flow, bent when operators tried to close it and remained a few inches open during the flood, the report said.

This meant that river water was pumped into the distribution network. 

The sluice gate and flap gates have since been repaired, Vanderzwaag said. 

Buyouts offered for Ptarmigan Court

Council passed a motion to offer voluntary buy outs to those living in Ptarmigan Court. The area was impacted heavily by the flood, and a berm system is not feasible for the area. The municipality was looking into the option of land swaps, but the municipality hasn't been able to secure necessary land from the provincial government for a swap. 

Council also passed a motion to implement a backflow preventer grant program. Council approved $1 million for the Sanitary Sewer Backwater Prevention program, which will reimburse homeowners up to $3,000 for the installation of a backwater valve. 

The municipality will accept applications for that program in March 2021.

Comments

To encourage thoughtful and respectful conversations, first and last names will appear with each submission to CBC/Radio-Canada's online communities (except in children and youth-oriented communities). Pseudonyms will no longer be permitted.

By submitting a comment, you accept that CBC has the right to reproduce and publish that comment in whole or in part, in any manner CBC chooses. Please note that CBC does not endorse the opinions expressed in comments. Comments on this story are moderated according to our Submission Guidelines. Comments are welcome while open. We reserve the right to close comments at any time.

now