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Keller Foundations’ role in Toronto’s new underground transformer station

By Jim Chliboyko

When the construction of Toronto’s new downtown transformer station was announced, what was arguably the most amazing thing was the news that it was to be the city’s first downtown transformer station built since 1955. The power being routed through the new transformer station will not only supply Toronto’s financial district, but will give the existing infrastructure a bit of a break and an opportunity to get some maintenance done on the rapidly aging Windsor Transformer Station, a half-kilometre to the north.

Toronto Hydro’s estimated $195-million new station – located by the John Street CPR Roundhouse, a block or so away from both the CN Tower and Rogers Centre (the SkyDome) – is seen as the next step in strengthening the city’s electrical infrastructure. The company points out on its website that the population of the downtown area increased by 50 per cent in one five-year period alone (2006 to 2011), adding to increased electrical demand, and adding to the pressure on the Windsor station. The new station will add 144 MVA of capacity.

Occasionally, the transformer station is still referred to as the Bremner Transformer Station, though it’s recently been renamed the Clare R. Copeland Transformer Station (after a former chair of the Toronto Hydro board, who only just left the position in 2013 after 14 years as chairman). The area in question is at the southwestern corner of Rees and Lakeshore. It’s actually part of Toronto’s municipal parks system, known as Roundhouse Park, and the Roundhouse itself is considered a National Historic Site of Canada.

Isherwood Geostructural Engineers designed the shoring component of the project. Carillion Construction Inc. won the general contractor bid and, in turn, they selected Keller Foundations to perform the shoring and foundation work for the station.

When Ontario-based Keller Foundations project manager Graeme Smart was asked what the challenges on the project were, he replied, “I would say the complexity of the physical location of the site, the irregular shape of the site and an aggressive schedule.”

In terms of sheer numbers to do with shoring, Smart said, “The plan consisted of 425 vertical shafts for the secant wall, all one meter in diameter, and ranging from 40 to 60 feet in length. The site had two levels of rock anchor tiebacks, 187 of them total for 2,600 lineal meters of tiebacks. We used two Liebherr LB 28 hydraulic drill rigs with segmental casing to install the secant wall, and Klemm 806-3D drills for the tiebacks.”

Multiple five-person crews were on site for the installation of the secant wall with Keller forces increasing in numbers when the schedule called for tieback installation work to begin while the secant work was still ongoing.

It’s not only a tricky place to build such a station, but the Clare R. Copeland Transformer Station added a few new wrinkles to a typical hydro-related build. First, it’s only the second underground transformer station ever built in Canada. This particular transformer station will be the equivalent of four stories underground. Secondly, the place is so crowded that one particular historical building, the Roundhouse’s machine shop, had to be carefully and painstakingly dismantled in order to be properly rebuilt after the station was completed. (The machine shop will eventually contain some of the equipment for the station; the dismantling will give it the chance to be properly upgraded before it is repurposed.)

The site also had a few surprises in store for the crew.

“If you look at the history of that site, apparently there’s an old sunken ship around there. We did hit an obstruction on the east wall at the south end of the site,” said Smart, who added that they never found out the exact source of the obstruction. This is not unprecedented; parts of the Commodore Jarvis, an old wreck that had been destroyed by fire in the early 20th century, were unearthed during the construction of the Air Canada Centre.

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Piling Canada is the premier national voice for the Canadian deep foundation construction industry. Each issue is dedicated to providing readers with current and informative editorial, including project updates, company profiles, technological advancements, safety news, environmental information, HR advice, pertinent legal issues and more.