Below the surface: 3,000 kilometres of underground roadways and tunnels
In 1979, the Canmore mine closed after 90 years of operations. It's easy to see how much has changed: the town's population has soared with an intentional shift toward tourism, recreation and real estate as the main drivers of its economy.
Underground, however, a complex system of more than 3,000 kilometres of underground roadways and tunnels exists below the western slopes of town on the Three Sisters property.
To develop infrastructure on disturbed lands such as these requires a whole new level of engineering expertise and mitigation techniques. Even with the brightest people and the best available technology, the opportunity for structural failure on undermined lands is always present.
History has shown us, more than once in Canmore alone, that it's not possible to mitigate undermined land to a 100 per cent level of safety from loss of property, human life, or damage to municipal infrastructure. So what happens if our best mitigation attempts don't last?
Accidents happen: the Dyrgas Gate shaft collapse
If you know a little about geology, you know that the earth is in a constant state of change. In Canmore, building on the surface is complicated further by the geologic structure of the mountainous environment and the complexity of the underground workings of the former Canmore Mines.
It's no surprise that it's difficult to mitigate perfectly for settling or collapse of the surface.
In 2010, an old mine shaft collapsed, taking out a public trail on Dyrgas Gate, located on Three Sisters lands. If you walk or ride your bike in the area, you're likely familiar with the now fenced-off area that surrounds the collapse site.
Because the sinkhole happened on public property rather than private property (engineered plans intentionally avoided placing any homes directly above the mitigated shaft), the developer responsible for mitigating these collapsed mine workings has considered it "a successful example of mitigation.” [Source: Rocky Mountain Outlook, Nov. 10, 2016].
With a potential price tag — paid for by taxpayers — of at least $600,000 spent repairing the Dyrgas Gate shaft collapse, there are some questions by local and provincial taxpayers about how successful the mitigation has been so far.
Who pays the bills?
The Dyrgas Gate mine shaft, which was mitigated (or engineered for safety to allow development on that property) is projected to cost Alberta taxpayers at least $600,000 to fix. It has been seven years, and attempts to repair the collapse have been unsuccessful so far.
What makes the Dyrgas Gate shaft collapse — and any other mine induced cave-ins that may appear in the future — an even more complicated issue for the town is that the provincial government does not indemnify (compensate or insure) the town for damage to infrastructure as a result of undermining on municipal land (despite contrary statements in the Canmore Undermining Exemption from Liability Regulation).
The Town of Canmore has been advocating with the province for some time to have these liability issues amended, but it's still an ongoing issue. There's a renewed need to come to a decision before the TSMV Resort Centre application comes forward; if it is approved, the development will largely be built upon undermined lands that will require extensive mitigation, which could put Canmore at risk if the province is not willing to assume it.
“The town has concerns about accepting any new infrastructure on undermined lands in absence of clarity from the province regarding liability,” said Michael Fark, general manager of infrastructure with the Town of Canmore.
To add to the confusion, according to the Canmore Undermining Review Regulation (Section 4(1)), developers are legally required to hold insurance on undermined property that they build on. However, it seems that Alberta's insurance companies won't provide insurance to developers on undermined land, so it's a bit of a conundrum. With pressure, the province might be able to enforce insurers to provide coverage for undermining, but that's not the current reality and it's perceived to be a long shot if it ever does happen. Until such time as developers are able to take out insurance on lands they develop, it's local taxes that pay the costs for future damages on both housing estates and municipal land.
In Canmore's case, history has also demonstrated that when developers declare bankruptcy (as they have done three times in the history of these lands, most recently in 2008), local and provincial taxpayers are financially exposed by any accidents that happen on the property.
Learning From Experience: A history of mining and development on Three Sisters Lands
This 23-minute video produced by Glen Crawford explores undermining issues and concerns regarding development on the Three Sisters lands. Retired mine engineer and expert on the Canmore Mines, Gerry Stephenson explains the history of what has gone on underground and the potential dangers faced by developing on these lands.
Improvements to mitigation techniques are in a constant state of evolution. The best available science, technology and engineering is always being employed by developers and municipalities to make sure people and property is as safe as possible. However, as mentioned above, 100 per cent certainty with any mitigation technique isn't Canmore's reality; unfortunately, unknowns and complications could always exist.
For more on current practices, watch this animated video produced by Three Sisters Mountain Village as part of its application for a Resort Centre ASP Amendment. The application would require extensive undermining mitigation in order to proceed if approved.
Thanks to all those who provided background for this section, and to the Canmore Museum and Geoscience Centre for sharing illustrations and information.
Have an hour to spare? Head on down to the Canmore Museum and Geoscience Centre for a deeper dive into what Canmore was like during the mining days.