On April 1, 2020, the Canmore Undermining Review Regulation (AR 34/2020) came into force. The regulation repeals and replaces Canmore Undermining Review Regulation (AR 114/97).


The Government of Alberta adopted legislation in 1997 to address the development of undermined lands in Designated Areas of Canmore subject to the NRCB decision. The legislation included three Alberta Regulations:

In 2010 a sinkhole formed in Dyrgas Gate under a municipal pathway. The Town of Canmore referenced the legislation in seeking remedy from Price Waterhouse Coopers (the agent acting as Receiver for Three Sisters Mountain Village at the time) and the Province, however legal interpretation of the regulation indicated that the Town was not protected from liability for direct losses from undermining.

The Province has been firm in maintaining the existing regulations that address indemnity (AR112/1997) and liability (AR 113/1997). At the request of the Town and Three Sisters Mountain Village, the Province undertook a review and update of the Undermining Review Regulation (AR 114/1997) to update and clarify the engineering and approval process, insurance requirements, and associated guidelines. The updated regulation came into effect April 1, 2020.

Summary of Changes

The following are a high level summary of changes from AR 114/97 to AR 34/2020.

Regulation Updates

  1. Changes to provide better definition of who a developer is for the purposes of undermining
  2. Fixed errors in the list of lands included in the regulation
  3. Provides a timeframe for registering an undermining report
  4. Considers input from the town including: better definitions of insurance requirements, and the introduction of a system of undermining reports that is more aligned with municipal planning documents and permits


The 2020 Guidelines to Evaluate Proposed Development Over Designated Undermined Lands in the Town of Canmore provide a comprehensive outline of steps to be taken in order to meet regulatory requirements at each stage of development and have been updated to align with processes that have evolved and developed in Canmore over the past 23 years since the first regulations were put in place.

Community Impact

Purchasing a home or owning infrastructure over undermined lands comes with risk. If subsidence occurs, it can cause damage to structures, utilities, roadways, paths, and green spaces. The regulation and guidelines aim to ensure those risks are defined and that they are reduced to defined thresholds comparable to other mitigated risks we accept on a regular basis (e.g. flood).

Undermining risks are reduced through engineering study as defined by the new guidelines and a ‘two seal’ process which requires an engineer to sign and seal the original report and an independent third-party reviewer to sign and seal a letter of compliance stating that the guidelines had been met. 

The original regulation allowed for significant development in Three Sisters Mountain Village over nearly a quarter century without detrimental undermining impact, with two notable exceptions. Those exceptions include a collapse of undermining mitigation along the Three Sisters Parkway resulting in a roadway failure, and subsidence of a pathway over an airshaft forming a sinkhole in Dyrgas Gate. Both failures involved water lines which likely ruptured due to settlements, contributing to the failures in the mitigation in both of these instances. The updated guidelines address these failures by requiring a higher standard of mitigation for pathways and roads, and a standard for deep utilities that is equal to the high standard for building structures.