A black and white photograph of a group of men working in an underground tunnel. Their clothes are filled with mud and dirt.

Toronto’s Tunnels

This article continues the Heritage at Home series, originally launched in the Spring as a limited series, and offered during a time when we dealt with cancelled onsite programs and COVID-19 restrictions. We’ve decided to continue to periodically showcase stories that inform, challenge, amuse or bemuse.

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By Leslie Sinclair, October 8, 2020

Urban Legends and Unsolved Mysteries

Toronto is a city of tunnels.

It’s a city that tried to bury its creeks, had the vision to build a subway, and connected more than 70 downtown buildings to the PATH, 30 kilometres of pedestrian tunnel so conspicuous it’s hidden in plain sight. But we rarely think about the world beneath our feet, which shuttles our communications, transports our bodies, and brings us clean water.

Aerial view of a complex with multiple buildings and connecting roads visible. A more intensely developed area appears in the background.

A Secret Bunker

In early 2015, a conservation officer spied a large mound of dirt near the Rexall Centre, just south of York University.

Moving to investigate, he found a ladder leading down a hole 10 feet deep concealed beneath a piece of wood. The mystery only deepened when police were called. Their investigation revealed a sophisticated tunnel, roughly 10 metres long and six feet high. It had been painstakingly built using a pulley system to remove dirt as the tunnel was dug. The walls were lined with plywood, expertly ensuring structural integrity. Most intriguing of all: a wooden rosary that hung from a nail on the wall, a Remembrance Day poppy attached.

The tunnel’s proximity to the Rexall Centre, which was slated to host the tennis competition during the Pan Am Games later that year, caused some folks to speculate that it posed a security threat. But as Toronto police deputy chief Mark Saunders explained to the Toronto Star, “There’s no criminal offence for digging a hole.”

It was the work of Elton McDonald, a 22-year-old construction worker who had built the tunnel over the course of a year and a half with the help of a few friends. The project was the culmination of years’ worth of tunnel-building practice in which McDonald built, then filled in, many smaller tunnels. When he discovered the heavily wooded area near York, he envisioned the tunnel of his dreams.

As for McDonald’s mysterious rosary? A gift from his sister, to keep him safe.

York University Master Plan

York University’s Pedestrian Tunnels

Tunnels at York University have long been the subject of myth.

Siting his project on land near York, McDonald perfectly epitomized the university’s motto, Tentanda Via: The Way Must Be Tried. The tunnel systems at York have been important for student interaction with the campus throughout its history but reliable information about them is difficult to come by.

Multiple utility tunnels criss-cross the campus, including the steam tunnels – which have grown their own body of lore – used for transporting high-temperature steam from a central boiler to all campus buildings. It was a small segment of this utility tunnelling that grew to become the pedestrian tunnel system, between Petrie Science Building and Steacie Science Library.

York is built in the Brutalist style, and the need for students to be able to quickly and comfortably get around a large campus consisting of hulking concrete buildings in winter was considered in the university’s original 1963 Master Plan.

By 1969 a segment connecting the Murray Ross building to the central square was underway, with the expectation that it would be linked to the initial connection between Petrie and Steacie. By 1972, the university was opening another channel from College Complex 1, to Stedman Lecture Hall, which by then had already been connected to the Farquharson Life Science Building.

Perceptions about safety and security on campus shifted dramatically in the 1990s. Students were advised against taking the tunnels, especially alone. Between 2002 and 2007, York quietly closed the tunnels between Stedman and College Complex 1, stating that the area was prone to incidents and difficult to monitor, not to mention the constant battle against graffiti.

Modern building dominates image. Building comprises a large curved roof made of interconnected glass panels.

Roy Thomson Hall

During its construction, Roy Thomson Hall became the scene of one of Toronto’s greatest riddles.

Digging its foundations, workers struck an unforeseen wall. Behind it was a 10-foot square room containing a chair, a table, two empty mugs, and a locked safe weighing several hundred pounds. The room was located directly under Simcoe Street. Although the contents were brought to the surface, bizarrely the safe vanished along with any clues it may have contained as to the room’s origin story.

A similar tunnel was discovered under Wellington Street but fears of collapse prevented it from being entered. Perhaps the tunnels were related to the past uses of the Roy Thomson Hall site, previously home to Ontario’s Government House and a Canadian Pacific freight office, but both sites were filled in without a solution.

Old coloured postcard showing large Victorian building with castle-like building behind it. A rock-lined pathway appears in the foreground.

Classified: Casa Loma Stables

Toronto’s war effort was kept out of sight.

In 1905, Sir Henry Pellat purchased land which had been the private golf course of Albert Austin of nearby Spadina House. Anticipating construction of Casa Loma, he hired E. J. Lennox to design and build the stables. Even Sir Henry’s horses lived a life of luxury. Their stalls were crafted of Spanish mahogany; floor tiles were set in a herringbone pattern to prevent slipping; and every horse’s name appeared in gold at the head of its stall. When the castle proper was completed, it was connected to the stables by a tunnel. Here’s where the story gets interesting.

During World War II, the shipping lanes between North America and Britain were terrorized by German U-boats which lead the British to develop ASDIC, an early form of sonar that was vital in the battles of the Atlantic. But when the manufacturing plant was bombed, the Brits were left scrambling to find a new location to continue researching and developing the technology.

Canadian engineer, William Corman was charged with scouting ASDIC’s new home. Surmising that nobody would suspect a site connected to a castle that hosted spectacular dances every Saturday night, he chose the Casa Loma stables.

He was right. Even local councillors didn’t find out about the project until a decade later, after the war had ended.

A man in a black suit stands among munitions workers and inspects their work, which he is holding in his hands. On either side of him are several women in white uniforms and two men in lab coats. They are sitting or standing in front of a workbench with more munitions.

Undercover Golden Mile

More than four kilometres of abandoned tunnels lurk beneath Scarborough.

They are among the remnants of the General Engineering Company (Canada) Limited munitions plant, which opened in 1941, on nearly 350 acres of expropriated land. Incredibly, 170 buildings and the tunnel system were built in just five months. Sitting south of Eglinton Avenue and north of Hymus Road, and between Warden Avenue and Birchmount Road, the top-secret plant produced more than 256 million munitions for the Allied Forces. Its workforce of 21,000 was comprised of mostly women.

The tunnels, which housed GECO’s electricity, water, steam and compressed air lines, along with transformer vaults and switch rooms, extend southeast from Eglinton and Warden. The plant operated around the clock, six days a week. Placing this infrastructure underground ensured that production would not be interrupted should an explosion occur in one of the workshops.

Roughly 20 of the GECO buildings remain in use by current commercial and industrial businesses.

Old coloured postcard showing a big playing field and several small figures dressed in white. In the background several Victorian brick buildings are visible.

Digging into Mental Health

Lakeshore Psychiatric Hospital’s first patients built a network of tunnels beneath it.

In the 1870s, the Provincial Lunatic Asylum (now CAMH) was overcrowded so authorities sought to separate patients suffering from less severe mental illness from those they called the “incurables”. Opened in 1889 on a site of a provincial farm, Mimico Asylum fulfilled this need and was considered progressive at the time. Its cottage system design was meant to create a hospital that didn’t feel like an institution. As productive work was considered therapy (and the cost-savings was undeniable), patients built most of the asylum’s buildings, as well as tended the orchard and on-site farm.

They also built a system of tunnels beneath the cottages. Connecting all the buildings of the hospital, the tunnels provided access for staff, a way to move patients from building to building, and a mode of transporting food, laundry, and equipment.

The asylum’s name changed several times before it became the Lakeshore Psychiatric Hospital in 1964. Ultimately, the hospital closed in 1979. In 1991, Humber College signed a 99-year lease on the property and renovated the buildings for its Lakeshore Campus. Humber typically limits the tunnels to staff members but on occasion grants tours through its Interpretative Centre.

Map showing several locations near Toronto's waterfront and the islands with dashed and solid lines linking them indicating existing and expanded infrastructure.

How to Cool a Modern City

What creates enough energy (55 MW) annually that it can power eight hospitals?

The largest of its kind, the Deep Lake Water Cooling System operated by Enwave harnesses the renewable cold temperature of the water at the bottom of Lake Ontario to cool hospitals, data centers, educational campuses, government, commercial and residential buildings.

Cadillac Fairview was one of its first customers, connecting TD Centre’s six office towers to the system which comprises 4.3 km of bored tunnel beneath the downtown core. Since Brookfield Place connected, it has completely eliminated its need for conventional chiller plants. In 2018, the complex consisting of two office towers, the Allen Lambert Galleria, and the Hockey Hall of Fame, saved enough electricity to power a small community.

Though much of the system was constructed in relative secrecy, because of its size, the network is considered as significant an underground structure as the PATH system.

Group of people standing in a tunnel in hard hats and reflective vests.

Tunnelling into the Future

What’s next for Toronto’s tunnels?

Underground space can be used to support livable, resilient, and sustainable cities. What that means is limited only by our imaginations. Maybe it’s more innovative infrastructure projects like the Deep Lake Water Cooling System that can propel our aging systems into the future. It might mean placing more facilities that don’t need to be on the surface underground in order to prioritize green space (a good example of this is Ryerson University’s recreation centre which exists below the only green space on campus). Or what if we think bigger? Like the designers of New York’s Lowline, for example, who upended the notion of where green space needs to be with the goal of converting an underground trolley terminal into a park. As Toronto’s density continues to increase, it may be time to look down. We’ve already gone up.