Barges in Lake Ontario continue outfall tunnel work for Ashbridges Bay Wastewater Treatment Plant

Barges in Lake Ontario off Woodbine Beach are working on a new outfall tunnel for the Ashbridges Bay Wastewater Treatment Plant. The entire project is expected to be completed by early 2024.


The construction of the new outfall tunnel for Ashbridges Bay Wastewater Treatment Plant has been a work in progress since the inception of the project last year.

Last summer the appearance of a barge and crane visible from the shores of Woodbine Beach stirred the curiosity of some Beach residents as in-lake construction began. Read the original Beach Metro News story here:

Since then construction has been progressing well.

“The marine construction (risers) are partially completed, the shaft is almost complete and the starter tunnel is almost complete,” said Susan Pape, a senior communications coordinator at the City of Toronto, in an interview with Beach Metro News on July 22 of this year.

According to the construction notice released by The City of Toronto in January 2019, the project would include 50 in-lake risers, and that the shaft would be approximately 85 metres deep and 14 metres in diameter.

The starter tunnel will eventually be a 3.5 kilometres long and seven metres in diameter that will tunnel into bedrock using a tunnel boring machine.

The purpose of the new outfall tunnel is to increase its capacity and better convey the effluent from the plant, as well as to better operate under high flow conditions, mainly during rainstorms.

“Crews will continue with the marine work and installation of the risers in the lake. Tunnelling with the tunnel boring machine is expected to start later this year,” said Pape.

Pape said that the barge in the lake should be demobilized before this winter.

The entire project is expected to be completed in the winter of 2024.

The new outfall tunnel will improve water quality at the city’s shorelines and beaches after completion.

For more information on the new outfall tunnel, see the construction notice at

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