A PDF version of the presentation is provided here as a supplement when watching the video.
Thank you for those who took the time to attend the Undermining Information Session. For any community members who were unable to make it, TSMV is pleased to share a video of the presentation.
The information session outlined the history of mining in Canmore, provided an update on new regulations and processes for addressing impacts and mitigations, outlined undermining aspects of the Three Sisters Village ASP, explained how hazards are identified and risks mitigated, answered questions from the community and more. The presentation included a 3D animated model of the Three Sisters Village ASP area and the mines beneath.
Due to a lot of curiosity and lack of time, TSMV was unable to answer all questions asked during the Undermining Information Session. Please see below for an FAQ that addresses these questions.
What types of failures or hazards have been experienced to date on the TSMV lands? And how have they been managed or mitigated?
Collapsed rock above a mined seam would likely be fractured, probably not as much at the higher curvature area. Where collapse has occurred, there can be movement along the fracture planes, maybe small movement but movement nonetheless. Once an area is fractured, unless they have annealed (sealed off by mineralization) they can be conduits for fluids. Could you provide information from drill holes through some of these collapse features in the Three Sisters Area?
On your slide #2, you demonstrated that Rundleview development had not been undermined. I was working on building the roads there when that development began. I was witness to the sinkhole (1st cul de sac on the left) that appeared and resulted in the abandonment of the road for homes. With that in mind, and the fact that you have not acknowledged this mining activity area on your maps. How can you have confidence in your mapping? (NOTE: author of question originally referenced Homesteads, and then corrected to Rundleview in the session).
What are some examples of "structural mitigations" that you would specify in areas of expected subsidence?
Who makes the final decision on what type of building can or cannot be built on undermined lands?
It is important to note that rather than being an absolute indicator of where a development may or may not occur, or the extent or type of mitigation required, the hazard zone map is used to highlight those areas of land where greater investigation and engineering may be required prior to proceeding with development or construction. At the final stage of investigation and planning, precautions to be taken and mitigation actions required will be determined based on the specific conditions under consideration and nature of the development proposed.
With regards to liability due to undermining, you say in your FAQ, “It is not reasonably possible to specify in advance who is liable should an issue arise”. I will not paint a worst case scenario here but this development exposes Canmore (and possibly Alberta) taxpayers to potentially exponential liabilities due to undermining. Furthermore, you are saying the land is safe to develop yet there is an existing sinkhole in the current Three Sisters Development that has never been addressed.
Once the work that meets Alberta Regulation 34/2020 is completed for development of structures, development can proceed using Alberta Building Code practices as appropriate with the risk arising from undermining being like the risk of any geotechnical condition arising (no development or construction of any structure anywhere is zero risk, risk is just managed to acceptable levels as appropriate). A notable exception difference to undermining approaches within TSMV is that they are subject to a regulated process and independently reviewed by third parties prior to utilization of the recommendations, which does not normally occur with geotechnical, structural, architectural and other professional disciplines involved in building and development. Existing sinkholes on the unfinished golf course were noted as well-known and monitored, but they have not yet been mitigated for development purposes yet. They would be addressed during development of the Village ASP in future.
If TSMV is confident in their exploration and mitigation of mines, why doesn’t TSMV offer a bond, or provide some sort of monetary assurance of their belief that development can take place with minimal to no risk. Instead, TSMV explicitly transfers 100% of the liability to landowners (buyers/Town) upon sale/transfer of the land.
We would also correct and clarify the portion of the question about transferring liability, as while the regulations only explicitly require that TSMV or other builders and developers working within the designated area have to file a caveat on title for disclosure to future end buyers, TSMV actually goes over and above that requirement by also disclosing within land sales contracts that a) the purchaser has to explicitly acknowledge that the land is affected by Alberta Regulation 34/2020; b) the purchaser assumes full responsibility for complying with the regulation after taking possession of the land; c) the purchaser acknowledges that they may incur additional costs during construction with respect to undermining mitigation (if required) and d) that a caveat would be filed against the title to the land. These types of disclosures are quite normal in real estate contracts. Item (b) is not a TSMV driven transfer of liability, it’s actually an acknowledgement of the requirements of Alberta Regulations 34/2020 such as Sections 1(1)(h), 1(1)(k), 5(2), 6(2) and 8 or others. The intent is to make sure that future builders, developers are aware that they may need to undertake undermining work as a part of their development permit as per Provincial requirements, and to make sure future landowners know that if a building needs to be rebuilt, it must be rebuilt in accordance with existing undermining recommendations in full or a new undermining report may be required if redevelopment occurs.
In relation to the chart that ranked levels of risk from low to high, who decides what level of risk is acceptable? Is it the town council, engineers, the taxpayers?
Building codes and other industry engineering standards have long been based on the concept of acceptable risk, which involves establishing standards that balance the costs of subsidence-resistant construction or ground treatment for any geotechnical consideration against the chance of incurring unacceptable losses in future events.
Generally, risks to loss-of-life are always considered in all undermining work in the new Guidelines, and accordingly no occupied structure within a developed site should pose a risk to the public that would present exceeding an annual risk of mortality of 1:100,000. This is similar to the 1:100,000 Safety Risk Tolerance outlined in Section 3.5.1(b) in the Town of Canmore’s Municipal Development Plan for new development for steep creek considerations.
Is there a map of the planned development that is overlaid on the risk map with the red, yellow, green, etc. colours? This would help us understand what is currently planned for the higher risk areas. (Also asked and similar from a different person: Why did your report and presentation not show the types of developments (e.g., roads or hotel) over top the colour coded hazard zones?)
The Undermining Risk map (Map 8) is not an absolute indicator of where a development may or may not occur, or the extent or type of mitigation required, but rather a map that is used to highlight those areas of land where greater investigation and engineering may be required prior to proceeding with development or construction. At the final stage of investigation and planning, precautions to be taken and mitigation actions required will be determined based on the specific conditions under consideration and nature of the development proposed.
When I bought a bare lot from TSMV I had to accept 100% of the liability. I’m trying to find the purchase contract but it stated that I have read the undermining report on title and accept all liability upon land transfer. Are you saying that isn’t the case? TSMV would have been liable if upon building I found an unmapped shaft, or improperly mapped shaft, that affected the construction of my home?
As noted in the answer to the question noted above, the intent is to make sure that future builders, developers are aware that they may need to undertake undermining work as a part of their development permit, and to make sure future landowners know that if a building needs to be rebuilt, it must be rebuilt in accordance with existing undermining recommendations in full or a new undermining report may be required if redevelopment occurs.
TSMV does not generally sell bare lots that require further undermining assessment or mitigation to members of the general public, but rather such lots are sold to experienced builders on an informed basis, as some types of undermining mitigation may need to be considered as a part of building design. For individual lots sold to the general public for single family houses, the undermining considerations have already been addressed, as was the case in the Cairn’s on the Bow or Stewart Creek Phase 3 for example.
Do you expect there will be some level of risk even after all the mitigation?
Further to Chris’ comments on mitigated vs non mitigated, I am concerned that some “mitigated” sites may still present some danger. For example, the collapse on Dyrgas Gate. This happened in the middle of the night on the public pathway where the shaft was “properly” mitigated. A person walking on it would not have plummeted down the shaft but potentially been crushed by the boulders and materials on top of the geotextile as it collapsed. Have mitigation practices changed since this was originally done? (In addition to this question, someone noted: In addition to the danger, the issue was that the Town and Developer fought for years as to who had to fix it (years and years later).
Since 1997, areas within 500 m of any occupied development within the designated area in TSMV have all required public safety to be addressed to prevent such scenarios and are also periodically reviewed by qualified professional engineers to check for any changes in conditions that need to be addressed.
To clarify, the Town and TSMVPL did not discuss who had to fix Dyrgas, as unfortunately the project was in receivership prior to current ownership when the incident occurred, so those discussions occurred between the Town and the receiver at the time. The Town did discuss the situation with the Province of Alberta, however, and it was found that the Town would not be able to seek remedy from the Province as the Town’s Indemnity Agreement with the Province dated May 5, 1999 excluded such recourse. Ultimately, the site was repaired with a mitigation that is an improved version of the same type of mitigation Norwest and Golder had previously installed.
You already have 2 fully approved ASP's from 2004 for a Resort Centre and Golf Course. With CoVid, Golf has surged with interest and is expected to increase in the future - an added value to a resort area, business opportunity and it could be finished. Why are you not just moving ahead with what you already have been given the green light on in 2004?
Great and thorough presentation. Based upon the information given, I would not hesitate to inhabit the areas that are mitigated. I am not seeing, or hearing that there are areas that cannot be mitigated by common geotechnical and structural work. Can the recorded session be made available to the public? Thank you...well done.
You mentioned Rossland B.C. as an example of a town that has built over undermining. What towns have successfully built over undermined areas?
• Nottingham, UK
• Newcastle, UK
• Cornwall, UK
• Lethbridge, Alberta
• Edmonton, Alberta
• Val d’Or, QC
• Murdochville, QC
Along with many others. There are also other significant areas of the United States, such as the east coast, that have undermining impacts from coal mining.
It is important to note that undermining was not an uncommon risk in areas that were part of early resource development. While there are municipalities that have experienced issues with undermining, a very common theme among them is that they do not have the type of regulatory environment and government approved guidelines in place to ensure proper engineering work is done and disclosed to future buyers that TSMV has. TSMV is in an exemplary position in that the workings are well documented, and programs are in place to ensure that development over undermined areas is done in a manner to address residual risks responsibly, and with third-party review.
I heard that the developer and mining engineers only have to carry insurance and bonds for 8-10 years. Is this true?
Has the flooding hazard been thoroughly researched in these proposed development areas and what is the flood interval and scale of flooding on the alluvial fan referenced in the lidar?
Several Steep creek hazard studies have been undertaken by both the Town and TSMV for both the Village ASP area and the Smith Creek ASP area. You can find them at https://tsmv.ca and https://canmore.ca/projects/mountain-creek-hazard-mitigation/creek-resources With respect to Three Sisters Creek steep creek hazard on its alluvial fan, the vast majority of the existing hazard potential impacts the existing developments of Three Sisters Creek and Ridge areas, as shown on Map 6, Section 7.8, Town of Canmore Land Use Bylaw 2018-22. TSMV and the Town of Canmore have been jointly planning appropriate mitigation measures that could be constructed to protect both the existing developments and the proposed Village ASP developments should the ASP be approved by Council.
What approximate portion of the TSMV will become property of the Town of Canmore, and is the Town of Canmore then liable for any subsequent undermining issues that could occur?
Currently, TSMV is at the ASP stage of the planning process, and as such, determination of specifically which areas will become the property of the Town of Canmore is premature as an Area Structure Plan does not generally provide information of future ownership. This is determined more appropriately at the subdivision stage of the planning process.
However, there are some aspects known now that may be helpful. For example, the limited amount of the Village ASP land area (approximatley 5%) that have steeply dipping or sub-vertical workings are not anticipated to become Town of Canmore property as TSMV plans on generally retaining these lands as part of the Resort Recreation Amenity Area shown in the Village ASP. In addition, generally municipalities in Alberta can end up owning up to about 40% of a typical subdivision for parks, roads, public utilities etc., however it is likely that the Town would end up with less than this as some of the roads or urban squares shown in the concept would likely to be privately owned with public access agreements (typical for condominium roads for example).
Please note: The liability aspect of this question was addressed in other questions focused on liability in this FAQ section.
Gerry (Stephenson) had mentioned that the proposed Three Sisters Village area had extensive surface mining that was back filled with whatever was available including organic matter. If I remember correctly, he had said that any development in this area will result in constant settlement issues due to improper backfilling. Are you also considering this issue, or just focusing on mine shafts below the surface?
Surface mining activity and impact in the Village ASP is actually not extensive but is less than 5% of the ASP area. Undermining assessments are not limited to just below ground impacts, but also includes previous surface mines (an example of such a mine is the current Quarry Lake park area). The previous surface mine within the Village ASP is one of the largest reasons that a limited area is marked in red on the Hazard Zone Map, and all surface mines within the ASP areas are already being considered as part of the ongoing and future work including mitigation as required. Several boreholes have been advanced in the area of the surface mine previously.
Notably, TSMV plans on generally retaining ownership of the lands identified as the Resort Recreation Amenity Area shown in the Village ASP, which would include where the previous surface mine works are located.
I see on your LIDAR that the sinkhole on Dyrgas Gate did not show up. Is it possible that other unknown features exist?
This question was answered during the live presentation. To summarize, as the known shaft (B14) was mitigated for public safety by Norwest in the late 1990s and additional public safety mitigation undertaken by Golder in 2003 for the Three Sisters Creek subdivision, LIDAR would not have picked the presence of the shaft.
LIDAR is just one tool used as a part of the process of evaluation of undermining (and is also used for other purposes like steep creek evaluations) and is not intended to be used in isolation. It is possible that localized undermining impacts have not yet expressed themselves at surface; however, the general locations of where such impacts may arise are known due to the availability of the high level detailed maps prepared by that previous Canmore residents that worked in the mines and preserved by the various levels of government, the high number of boreholes and studies now advanced across the site and other information. Appropriate measures are undertaken in known areas, including fencing, temporary backfilling, setting back development (as was done around B14 off Dyrgas) until such time as the need to mitigate each area beyond the level needed for preventing public access or public safety is required for development purposes.
I’ve heard that there will be a perpetual caveat on deeds to say that the homeowner knows that his house is built over lands that may subside. Is that true? Why would that be necessary? Will homeowners be able to buy insurance for subsidence with this on their deeds?
Within the designated area identified in Alberta Regulation 34/2020, this is correct. In fact, the placement of such a caveat has been a requirement for all TSMV developments in the designated area since 1997. This is prudent so that future buyers are formally and legally made aware through their purchase processes, including future resales, that their property has been assessed for undermining purposes. Several undermining reports, such as the one placed on the titles for the lots on Stewart Creek Close, conclude that undermining is not impacting the lands, while others document the below ground mitigation completed or structural recommendations within their buildings. This is done so that all buyers in the designated lands of TSMV are informed purchasers and can make their own decisions about potential purchases. Only the designated area within TSMV after 1997 has the ability to require these undermining caveats, and so older areas like Peaks of Grassi or Homesteads Phase 1 do not typically have such a caveat despite undermining work being completed in those areas. There have been no issues that we are aware of with obtaining typical homeowners insurance with these caveats, and we have had a couple of insurance programs review the caveats and process carefully in the past.
What about Public land liability? Chris did not clarify the Town’s liability for subsidence under utilities, roads, parks, etc.
One of the changes made within the 2020 undermining regulations and guidelines was that risk guidelines were reviewed and approved by the Province of Alberta for parks, roadways, pathways and utilities with the input of the Town of Canmore. The risk guidelines are now defined based on the consequence of damage or impairment of safe human use of these spaces. Underground utilities are now treated the same as buildings, which is new in the 2020 guidelines and regulations. These new risk guidelines bring the potential exposure to the Town of Canmore to potential impacts to be similar to any other area of Canmore for potential geotechnical risks.
It looks like you use a massive amount of material to paste or backfill old mine shafts. How does that material hold up to ground water erosion? And collapse over long periods of time? Also, we know cement is a huge CO2 emitter. What about the cement like substance you use for pasting? Is it similar?
The amount of material is actually relatively small volumes given the impact such a mitigation has. For example, pasting a notable tunnel beneath the Three Sisters Parkway near Dyrgas required only 150 m3 of paste to be placed. This was an older mix that had about 1/5 of the compressive strength of a typical sidewalk, and so used about 10,000 kg of cement and about 20,000 kg of waste product flyash along with about 300,000 kg of locally sourced aggregates and water. In Stewart Creek Phase 1, which was one of the larger programs, about 8,400 m3 of paste was used for roads, utilities, and other public spaces, however, the amount of cementitious materials (portland cement and waste product flyash) was reduced by over half compared to the Parkway paste program due to less compressive strength required (approximately 2% of a typical sidewalk).
The material is essentially a very weak concrete mixture when it sets, and so it holds up to groundwater conditions without issue, nor does it collapse over time (generally concrete mixes generally get stronger over time). Use of waste product flyash reduces CO2 impacts from the use of portland cement, and as noted the paste material incorporates far less cement materials than a typical sidewalk, curb, basement foundation and other concrete structures. It should be noted also that small void is left at the top of the fill pour, this aids in allowing any water flow to continue, but is not expected to erode over the time frame to cause any significant removal of material or support. These flows are so low such that potential erosion would be measured in geological time.
In your ‘bridge’ analogy, you know where the void is. As Gerry Stephenson said, there is no good map showing all the mines in the area. You say the TSMV would be “equivalent to building anywhere else in the Bow Valley”. Why do you think your map correctly identifies all the mines?
This question was partially answered during the live presentation. To summarize, the underground mines are very well mapped in a high level of detail, a credit to the Canmore residents who worked in the mines in the past, and to the levels of government and others responsible for their preservation. While there is no one “master map” showing all the details of all the mines in the area, there is a collection of maps that does document the mine working very well. Some of the surface mines were not mapped as well, but their extents are able to be determined via air photos, historical records, field assessment and drilling. Between the excellent quality of the historical information, the field assessments, the influence of the underlying geologic conditions, the drilling programs and other information available, there is a very high level of correlation of mapping and actual extents of the mines.