THUNDER BAY — The city is looking to identify the source of a sewage backup that has impacted several homes located near a worksite where a collapsed culvert on River Street is being replaced.
Homes adjacent to the worksite have experienced sewage backups multiple times in recent weeks, multiple area residents reported.
The city confirmed an estimated four homes were impacted Tuesday morning by sewage backups.
Work to replace the culvert, which collapsed in May 2022, required the removal of sanitary sewer pipes that had been supported by the structure. In the meantime, pumps are carrying sewage through temporary lines until a new culvert is in place.
Project engineer Mike Vogrig said Tuesday's backup likely occurred when as "surge of inflow" into the sanitary sewer exceeded the capacity of both a main pump and backup pump for around 15 minutes shortly before 9 a.m.
The city was still investigating the cause of that inflow, he said Wednesday, speculating it could have involved an infiltration of water from outside the sanitary system, like a storm outlet.
“It’s a little bit mind-boggling the amount of flow that came through that sanitary sewer in such a short time,” he said. “So not only are we trying to design a solution on site, we’re trying to identify where all the flow was coming from in the first place.”
Vogrig noted the pumps had been chosen to meet the estimated peak flow of the sanitary sewer, based on water level readings taken in the sewer before work began.
The city is looking at the possibility of introducing more powerful pumps, Vogrig said.
The city was aware of previous sewer backups in the area of the worksite about a month and a half ago, he added, but those were believed to have been addressed.
At the time, the city established a protocol to ensure communication with contractor Taranis when city crews conduct work like flushing hydrants in the area, which can cause sewage inflows, explained Vogrig.
“They have been doing that and we hadn’t seen [another] issue until [Tuesday] morning,” he said, when no such work was occurring nearby.
One neighbourhood resident said it was the fourth time they had experienced a sewage backup in recent weeks.
Another said their basement had been filled with over a foot of sewage.
Affected homeowners have been directed to consider filing insurance claims with the city if they sustained damage, Vogrig said.