Keller has constructed a diaphragm wall as part of Waterfront Toronto’s C$1.25bn (£732M) project to revitalise Toronto’s Port Lands neighbourhood and protect the city from flooding.

The Port Lands Flood Protection and Enabling Infrastructure project (PLFPEI) aims to transform 290ha of Toronto's Port Lands area – an industrial waterfront zone prone to flooding – into a new downtown neighbourhood called Villiers Island.

The project will also provide the site with critical flood protection by creating a naturalised mouth for the Don River. This will be surrounded by new parks, green spaces, public amenities and a new wetland to support native species.

The PLFPEI first broke ground in November 2018, with Keller North America joining the project in December 2020.

Keller has recently completed a diaphragm wall for the first phase of the project.

The diaphragm wall was designed to provide a temporary dam and support the excavation of the new west mouth of the Don Valley River into Lake Ontario, as well as create a permanent water cut-off for the new river channel.

Keller opted for a diaphragm wall over secant piles because of significant advantages including fewer construction joints, a stiffer wall with less overall deflection and lower costs.

The technique involves excavating a series of narrow trenches to create large panels reinforced with rebar, concrete and bentonite slurry.

The diaphragm wall was constructed using several different panel designs. These were supported by bentonite slurry, allowing Keller to excavate the trenches at depths of up to 44m with less than 0.5% vertical deviation at the tip of the panel.

For the operation Keller used a large-scale de-sanding and mixing process. This produced, recycled and redistributed the bentonite to the excavation site. It was also critical in maintaining a slurry head within the guide wall – and specifically above the water table – to prevent the panels collapsing during excavation.

When the excavation of the panels was complete, large prefabricated reinforced rebar cages, each weighing up to 22,680kg, were lowered into the trenches. Tremie tubes were then installed through the cages to pump in concrete. This process was repeated for each panel.

Project challenges included cold winter weather, contaminated soil conditions, managing large volumes of concrete and the Covid-19 pandemic.

Keller North America field technician Richard Males said: “Keller continuously seeks to provide the highest levels of safety, quality and efficient production for our clients, and this work demonstrated just that.

“This project will act as a stepping stone for the continued growth of the unique and advantageous diaphragm wall technology within the Toronto market and beyond.”

The project is one of the largest infrastructure projects in North America and one of the largest waterfront redevelopment initiatives ever undertaken in the world.

Creating the new 1km long  river valley,  r enaturalised  river  mouth   and  spillway will involve excavating 1.4M.m3 of soil - making the PLFPEI one of the most intensive earth moving projects in recent history.

The PLFPEI project is a collaboration between Waterfront Toronto, Toronto and Region Conservation Authority, the Toronto Port Lands Company and the City of Toronto.

Waterfront Toronto was created by the governments of Canada and Ontario and the City of Toronto in 2001 to oversee and lead the renewal of Toronto’s waterfront.

The next phase of PLFPEI will start this year. Once complete, other contractors will continue the excavation of the Don River towards Lake Ontario.

The whole project is expected to be completed by late 2023 to early 2024.

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