An aerial view of one of the temporary shafts used to excavate Enwave's chilled water distribution tunnels.

Mining in the Urban Field: Excavating the Enwave DLWC system

Michael Cook

For most of the second half of the last decade, the view from many of the condos and offices near Bay and College Streets in Toronto included the tantalizing hole depicted above. Approximately 15 m in diameter, this access shaft was nearly invisible at ground level, hidden as it was behind shrouded construction fencing and safety/reinforcing structures around the hole itself. However, the large crane vehicle stationed beside the shaft, and the gate signs describing the project as the work of McNally Engineering (history) did offer some hint as to what was going on within. A few photographs taken from the surrounding buildings eventually showed up online, but the fact that this large-scale, multi-leveled excavation project (and its three other construction shafts) went almost entirely unremarked on for five or six years is surprising.

"The likely reason that this work did not attract publicity is that only four mining shafts were used." - Mike McNally (McNally Engineering) and Kevin Loughborough (Enwave)1

To be sure, the obscurity and paucity of construction shafts was partly responsible for the fact that a major tunneling operation went unnoticed. But as far as I can tell, Enwave itself, which had previously trumpeted the construction of its Lake Ontario intake system and has continued to publicize each addition of a high-profile client (eg. the Hudson's Bay Company or Queen's Park) to the system, made no effort to explain or make people aware of the distribution system's actual construction. I've already discussed the invisibility of the distribution system in the city's public experience and in Enwave's promotional material, and I have posted photographs of the finished system. I will add a little to that discussion in the conclusion of this article, but my colleagues and I had the opportunity to see portions of the system while they were still being built, and I want to talk about that experience of an active excavation and finishing operation.

Rough shale walls, ceiling shoring and a work train, in the entrance to Enwave's Bay St. tunnel from the Hayter Street work shaft. (Mining in the Urban Field: Excavating the Enwave DLWC system)

Urban Excavation

Sometime around 2004-2005, soon after Enwave officially launched its deep lake water cooling system by hooking up a few clients near its pumping station beside the Roundhouse, an infusion of private debt offering allowed the company to proceed with sinking construction shafts for a broader distribution network servicing the core as far north as Wellesley Street. A central shaft at the intersection of Front and York streets facilitated much of the early construction, while shafts near the northern (>Hayter Street) and southern (Lower Simcoe Street beside the Gardiner Expressway) ends of the system remained in place until quite recently, allowing the rest of the DLWC network to be dug out and installed beneath our feet.

Because these shafts were open to sky, in the deep of winter the combination of snow and frozen groundwater probably made them all-but-unuseable on safety grounds. This was our first opportunity to see the system, climbing down many storeys of ladders into a frozen earthscape that apart from being underground looked positively alpine. Snow and ice coated the walls of the shaft, the exposed trench at the bottom that had once launched a tunnel-boring machine (now long gone) and the catwalk that led across from the elevator structure to the aluminum ladder into the trench. At the east end of the trench, the opening of an unfinished tunnel was bathed in incandescent light.

The unfinished end of the tunnel was a jumble of equipment, stockpiled materials, and workplace essentials (like a microwave oven). First aid kits, air horns, fire extinguishers, and a closed circuit telephone receiver hung in the entryway. Beyond this makeshift office and command point, a small mine train sat at the ready, and beyond the train stretched four kilometers of finished, semi-finished, and newly-bored tunnel on four different levels.

From the Hayter shaft, almost-finished tunnel curved away in two directions: north on an indirect route towards Queens Park, and south down Bay Street into the core (a third short stub line was later installed westward to the hospital and research complex at the corner of College and University). The Queen's Park tunnel was dark, smelled bad, and dead-ended at a set of valves. You can imagine our excitement when, after heading down Bay, we found the first ladder that led us to an additional level of tunnel.

But if the ramshackle work site at the top end of the system had intrigued us, what we discovered after following the cryptic series of completed tunnels southwest to Simcoe Street was something altogether more remarkable. Here, it appeared that we had missed the tunnel boring machine by a matter of weeks, rather than months. Heading up a makeshift aluminum ladder through the ceiling of a roughly cut valve chamber, we found ourselves in round, bare tunnel, wet and lovely. Wood and steel shoring held the ceiling of the tunnel in place, a narrow gauge rail line gave us something to walk on above the muck, and pneumatic air lines ran along the one wall. Mist snaked along the ceiling ahead us.

Excavated Simcoe St. DLWC tunnel. Notice that the rails split at bottom to allow workcars to be loaded on multiple sidings in the adjacent workshaft. (Mining in the Urban Field: Excavating the Enwave DLWC system)


We were standing beneath the intersection of Wellington and Simcoe Streets. A couple hundred meters to the north, contractors were (during business hours) laying and welding together the 1200mm steel pipes that sit beneath the concrete floors of all of Enwave's DLWC tunnels. This tunnel, the last major excavation in Enwave's roll-out, appears to connect the company's operations at Lower Simcoe Street and Pearl Street, and has since been completed with an additional steam line running through it to provide heat and backup power to the Simcoe Street chilled water plant and the Energy Transfer Facility at John Street. But when we saw it, concrete had yet to be poured, and for most of its length it was still an open, 3.5m round tunnel rather than the low, neck-torturing arches of the finished facilities. At the southern terminus, another access shaft, somewhat shallower than the one at Hayter Street, sat behind temporary fencing and work trailers in the shadows of the Gardiner.

Self-imposed Obscurity

To be sure, these small footprint work shafts were hidden in plain sight, unnoticed or unremarked on by nearly everyone even as work continued for a number of years. But if Enwave had wanted Toronto residents to know and care about its great tunnelling endeavour, it could have easily made it happen. That the company didn't speaks to the apparent priorities of its communications strategy: 1) Proving its technology to attract the $80 million in private debt necessary to roll out the system; 2) Promoting its service to corporate and institutional property owners to build its customer base; and 3) Investing in a landmark (the Enwave theatre at Harbourfront Centre) to raise its corporate prestige.

It is understandable and rational that these were Enwave's priorities as it took a new technology and implemented it on a relatively ambitious scale, and my point here is not to criticize the company for doing its job. However, what did get missed was an opportunity to engage with city residents on a more than superficial level about the incredibly interesting system that Enwave was installing not just out beneath the lake but throughout the core of the city.

As residents of Toronto, we have a political and environmental stake in Enwave's system, to be sure, but we also have a financial one -- the company received seed capital from the city, from Toronto Hydro, and from the province of Ontario to develop the DLWC system, and it has benefitted enormously from a close relationship with Toronto Water that has allowed it to make use of the pumping facilities at John Street and the Toronto Islands. Moreover, today's for-profit Enwave Energy Corporation emerged in 1998 from the reorganization of what was previously the non-profit Toronto District Heating Corporation. Enwave's ownership of the city's legacy district heating system (both the revenue stream and the very valuable physical properties that are occupied by its steam plants) almost certainly served to underpin the private loans that financed the new cooling system. It's unfortunate the company has largely neglected that history and that relationship with citizens of the city, and missed an opportunity to showcase and celebrate its place within the physical, subsurface landscape of downtown Toronto.

Don't forget to look at photographs of the completed Enwave Deep Lake Water Cooling distribution tunnels.

  1. 1. Mike McNally and Kevin Loughborough. 2009. "Toronto's Deep Lake Water Cooling Distribution by Tunnel." Canadian Tunneling Magazine.
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