Thousands of people cross over the Red River on the Fort Garry Bridge every day. Right now, we’re doing the opposite. We’re going underneath it. A tunnelling machine is working around the clock, carefully drilling deep below the river. It’s all so we can make critical sewer pipe repairs.
Why we’re going under the river
Under our streets and rivers are a series of sewer pipes. They take wastewater from our homes and businesses to our treatment plants.
Unfortunately, the sewer pipe crossing under the Red River near the Fort Garry Bridge failed in 2023. We put in place a temporary above ground bypass. This allowed us to keep the wastewater flowing to the treatment plants while we developed plans for permanent repairs.
A challenging repair job
This work requires highly specialized equipment and incredibly skilled equipment operators. Installing pipes on a vertical curve that moves through various ground conditions is also very complicated.
“This type of tunneling is very complex,” said Ryan Lucky, Design and Specification Engineer with Water and Waste. “It’s tricky to enter the bedrock through mixed soils and you need a contractor who knows what they are doing. Only a handful of them can do this type of work in North America.”
Another challenge we faced was it took a while for us to get some of the materials needed for this job. This is part of the reason why this critical repair has taken this long.
How we’re able to make a tunnel
To do this work, we’re using a special drill called a Microtunnel Boring Machine (MTBM). It was lowered 17 metres down into the earth. Last week, it started drilling a roughly 2.4 metre wide tunnel underneath the river.
“Microtunneling is ideal for installing large sewer pipes over long distances, under both existing infrastructure and environmentally sensitive areas like waterways,” said Lucky. “It allows us to install the pipes without disturbing the Red River.
The machine digs a tunnel with a rotating cutter head that grinds soil and rock, turning it into a slurry. That slurry is then carried through the pipes back to the surface where the debris gets filtered out. We're then able to reuse it.
A slow and cautious process
The MTBM is working 24 hours a day, in two 12-hour shifts, for a total of 18 days. Hydraulic jacks will push it through a path underneath the water. Eventually it will make its way upward toward the sewer connection on the other side.
It’s a process you can’t rush. The machine travels about 1.25 metres per hour and is operated remotely by employees on the ground. The only time anyone will go down to the machine is if it needs to be repaired.
Installing the new pipe
The MTBM isn’t just making the tunnel, it's also pushing the new casing pipe forward through it. Then, the two wastewater carrier pipes will be pulled into that casing pipe. That will carry sewage across the river.
This allows for an under-the-riverbed trenchless pipe installation without having to divert water or dig into the riverbed.
We expect the new crossing to be in service this summer. We’ll then be able to remove the bypass pipe we installed in early 2024.
Once it’s removed, we’ll lift the traffic restrictions near the bridge on Abinojii Mikanah.