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Draper Slope Stability Assessment Q&A

Who conducted the slope stability report and why was it completed?

The report was conducted by Thurber Engineering Ltd., (Thurber) a company with local experience and expertise in this specific area.

The report was prompted by resident concerns raised to the Municipality about the stability of the slopes in this area in the wake of the 2016 wildfire.

The scope of work for the Thurber Engineering 2017 assessment was to undertake a geotechnical study to summarize existing information and provide a preliminary assessment of the overall stability in this area.

How did you decide on the scope of this report?

The scope of this report was determined using data collected in a 1999 report completed by Terracon Geotechnique Ltd. That data was used to determine which areas required exploration.

Because the community of Draper consists primarily of Crown Land and Private Land, Thurber did not always have direct access to much of the prescribed area. Thurber obtained access to some of the private land thanks to the collaboration and cooperation of those land owners.

Why is this report only being issued now?

Following the 2016 wildfire, a slope stability assessment was completed for the Urban Service Area of Fort McMurray, with additional specific studies being completed for areas that were rebuilding after the fire. Draper had previously undergone a slope stability assessment (1999), which indicates that residents impacted by the slope must complete a lot-specific geotechnical assessment. When residents asked for a post-wildfire assessment, the Municipality completed it in June 2017.

The assessment included the review of existing maps and materials, aerial surveying and photographs and site reconnaissance followed by analysis of findings. That process takes time.

What are the implications for homeowners rebuilding in Draper?

There are five properties that were both affected by the wildfire and impacted by the results of the Draper Slope Stability Assessment.

In order to be issued the development permit required to rebuild, the owners of those properties will be required to have completed a lot-specific geotechnical assessment that must: must:

  • Assess whether the site is suitable for the proposed development from a slope stability perspective;
  • Identify any hazardous conditions that may impact proposed development; and
  • Undertake a detailed quantitative (i.e. slope stability analysis) and qualitative slope stability assessments to evaluate
    • the impact of construction on the stability of existing slopes and adjacent developments,
    • the impact of any slope instability issues on the proposed development and public safety, and
    • potential mitigation measures to protect public and infrastructure from any hazardous conditions.

Lot-specific geotechnical assessments have been a requirement for all new development since 1999.

Property owners who have concerns about slope stability related to the rebuild of their home are encouraged to contact the Planning and Development Department by email at planningdevelopment@rmwb.ca or by phone at 780-799-8695.

Have you contacted the property owners who are directly impacted by this report?

The Municipality has engaged with 12 property owners connected to eight properties within the community of Draper and will continue to work with them to ensure they understand what is required in order to rebuild their homes.

What if I have already received a development permit to rebuild my home in Draper?

If you have already received a development permit for a rebuild home in Draper, you can proceed as planned.

If you have further questions, you are encouraged to contact the Planning and Development department by email at planningdevelopment@rmwb.ca or by phone at 780-799-8695.

What are the risks to rebuilding in Draper?

The risks will vary from property to property, which is why a lot-specific geotechnical assessment is required before any development takes place in the area. Some of the potential risks include cracks in walls, uneven flooring, loss of functionality of a home, bowing and eventual failure of retaining walls, cracking of pavement and dips or humps in roads or driveways.

What are the risks to homeowners with standing homes in Draper?

Lot-specific geotechnical assessments have been required for all development in Draper since 1999. There remains a potential that ground movement since that time may have had an impact on standing homes and that continued ground movement may have an impact in the future.

Residents who believe their properties are being affected by slope movements should retain a qualified geotechnical engineering firm, registered in the Province of Alberta, to address slope stability concerns; quantify potential risks of instability on existing property and adjacent properties; provide short and long-term mitigation measures; and assess whether a slope movement would constitute a safety concern.

Given these risks, why was development allowed at all?

The rates of movement are slow, a rate of a few millimetres per year in particular areas in Draper, and certain residents were willing to accept the risk and build homes in Draper. The slope stability concerns in Draper are such that, with proper mitigation measures, safe development can be achieved without placing adjacent properties at risk. 

How are the slope stability concerns in Draper different than those in Waterways?

The composition of the soil varies between the two areas, with the colluvium in Draper being more stable and posing less risk. In addition, the lots in Draper are much larger and are spaced further apart, eliminating the concerns related to interdependency which are obvious in Waterways.

Why are you not buying my lot when you bought lots in Waterways?

The slope stability concerns are very different between Draper and Waterways. The long-term risk in Draper is reduced because lots are bigger and there are no underground utilities, eliminating the risks related to interdependencies and underground infrastructure upgrades.

Additionally, a comprehensive slope stability assessment was completed in 1999 for Draper, at which point residents planning to build on the slope were required to obtain lot specific geotechnical assessments. That requirement remains in place for all development, including rebuild properties.

I can’t afford a lot-specific geotechnical assessment and it is not covered by my insurance. What should I do?

Residents who face financial hurdles to completing the lot-specific geotechnical assessment required for the rebuild of their home are encouraged to contact the Canadian Red Cross by calling 1-888-553-5505 or visiting the Fort McMurray location at 10019B Franklin Avenue.

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