lake ontario construction

Construction project on Lake Ontario looks like a Viking invasion approaching Toronto

It may look like the beginnings of a Viking voyage to reconquer Vinland, but what appears to be a fleet of ships approaching Toronto is nothing you need to be too concerned about.

There is no invasion fleet here; the apparent battle group is actually a row of stationary barges working on the city's new outfall tunnel serving the Ashbridges Bay Treatment Plant.

The plant currently discharges its effluent through an aging outfall tunnel that was built in 1947. After three-quarters of a century carrying treated water from the city into the depths of Lake Ontario, the current outfall tunnel is nearing the end of its service life, lacking the capacity needed to serve a modern city and failing to measure up to today's regulatory standards.

A massive undertaking to replace the old infrastructure has been underway since December 2018, a mix of on-shore and off-shore construction bringing a modern $330 million tunnel 50 metres below the lakebed.

It will carry treated water on a 3.5-kilometre-long journey through its seven-metre diameter, lined with 13,600 precast concrete tunnel lining segments installed in 2,300 rings.

Though much of this work is subterranean — being carried out with a tunnel boring machine chewing below the lake bed — those out braving the elements on Toronto's frigid lakefront have noticed the group of eight barges looming in the distance, looking quite menacing in the cold morning mist.

And before you get the urge to start lighting signal fires from the tallest points in the city, these aren't seafaring Scandinavian conquerors or any other kind of invasion fleet.

These barges are simply drilling platforms for the fifty vertical in-line risers and ports that will populate the last kilometre of the tunnel and disperse the treated effluent in the lake.

It's a little bit hard to visualize with no frame of reference, but an informative video released by the city in 2021 offers up a detailed breakdown of how the project is unfolding.

Upon its projected completion date of December 2023, the new outfall tunnel is expected to improve water quality along Toronto's beaches and shorelines while addressing the current infrastructure's failure to meet provincial and federal regulations.

Lead photo by

Sean Marshall


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