At 2.2 miles, the Ashbridges Bay Treatment Plant Outfall will be the largest wastewater outfall in Canada. Graphic: Hatch Mott MacDonald
At 2.2 miles, the Ashbridges Bay Treatment Plant Outfall will be the largest wastewater outfall in Canada. Graphic: Hatch Mott MacDonald

As prime consultant, Hatch Mott MacDonald (HMM) will provide design and construction administration services for the Ashbridges outfall project, so named because a 2.2-mile tunnel will convey treated effluent from Toronto's Ashbridges Bay Treatment Plant into Lake Ontario.

The project also includes a drop shaft, a connection to lakebed risers constructed by barge from the lake above, and land-based plant connections. The tunnel's internal diameter is 23 feet.

“This project draw on our strengths in tunneling and in wastewater treatment,” says HMM Managing Director for Canada Michael Schatz. “We're proud to have won several awards for our work on the Keswick Effluent Outfall in Lake Simcoe and will bring the same care and expertise to this new challenge.”

The design and investigations phase of the project is planned through the end of 2017, with construction starting in the first quarter of 2018 and likely extending to the end of 2022.