Across Alberta, there are different requirements when it comes to developing sloped land. Below, we will discuss the requirements of the City of Calgary, as well as in 7 counties surrounding Calgary. All of the information below is taken from the respective Land Use Bylaw documents, but please contact your Development Authority to confirm your specific development requirements. If you require a slope stability report or a geotechnical investigation report, please reach out to us for a free consultation. We would be happy to discuss your project and provide any assistance you might require.
The City of Calgary
When it comes to developing a property within the City of Calgary, a Preliminary Slope Stability Evaluation is typically part of a preliminary geotechnical evaluation, which is documented within the Geotechnical Evaluation Report. This type of slope evaluation is required when “any existing or proposed slopes on or adjacent to the development site exceed 15%”, as is noted in the Geotechnical Report Guidelines for Land Development Applications.
If you have not completed a geotechnical investigation and submitted a geotechnical report for your permit application, the Detailed Team Review (DTR) completed by the City of Calgary can provide the following recommendation under Development Engineering:
“Provide a letter, for review and acceptance, under seal and permit to practice stamp, from a qualified Geotechnical Engineer that verifies the proposed development will not have an adverse affect on the stability of the slope and a minimum factor of safety of 1.5 is achieved to the satisfaction of the Geotechnical Engineer, Roads.”
If this appears on your DTR, please feel free to reach out to Factor. We have satisfied this request on hundreds of projects and will do our best to clear this item on your submittal in the quickest, most economical way possible. Where many geotechnical engineers automatically assume that you need to perform a costly geotechnical investigation and full topographical survey, we utilize our experience within the city and groundbreaking technology to satisfy slope stability report requirements and get your project back on track within days, not weeks (or even months).
Rocky View County
In Rocky View County, slope stability is split into two different requirements, a Slope Stability Assessment, or a Slope Stability Analysis. Within either of these reports, a qualified geotechnical engineer such as Factor Geotechnical will assess/analyze the site slopes. The slopes can be considered as part of the developable acre area if the engineer can certify the stability of slopes prior to, during development, and after development.
A Slope Stability Analysis Report is required when your land contains a slope 15% or greater with a vertical height over 2.0 m. This report is prepared by a qualified geotechnical engineer and will contain the following:
- A field site assessment/survey
- Recommendations on the suitability of the slope for the intended use
- Any setback distances required
This type of analysis will not require a full geotechnical field investigation to be completed. If any potential concerns are noted by the Geotechnical Engineer, a Slope Stability Analysis will be recommended.
A Slope Stability Analysis is a more detailed assessment that is required when your land contains a slope 30% or greater with a vertical height over 3.0 m, or for any major erosion area or area of previous slope failure. This type of report is also required if a Slope Stability Assessment has identified any areas of concern. The Slope Stability Analysis report or Slope Stability Geotechnical Report must contain the following:
- A Factor of Safety (Fs) for the existing slope or the proposed design slope profile
- A safe setback distance from the crest or toe of the slope, if required
- Recommendations for slope modifications to remediate any potential instabilities
- Recommendations to address post-development conditions and means and methods of mitigating any potential problems
- Discussion on the potential for a slope failure caused by septic fields, irrigation, access construction, stormwater erosion, etc.
- Test hole logs
This more detailed analysis will involve a geotechnical investigation where test holes are drilled and logged by an engineer. The information gathered from test holes will be used to perform modeling of the actual slope conditions to provide the required Factor of Safety for the existing and proposed slope profile.
Mountain View County
In Mountain View County, a Geotechnical Report addressing Slope Stability is required for developments adjacent to any bank if:
- The bank is greater than 3.0 m (10.0 ft) in height; and/or
- The bank is greater than 10% in slope; and
- The development is proposed within a distance equal to twice the bank height, measured back from the top of bank
In accordance with the Mountain View County Land Use Bylaw, a Geotechnical Report will be prepared by a qualified professional engineer accredited by APEGA. The report will identify and assess the subsurface soil and groundwater conditions liable to affecting suitability of the lands to support the proposed development.
Foothills County
Within the MD of Foothills or Foothills County, the minimum development setback on a lot adjacent to a slope of 15% (8.3 degrees) or greater is to be a minimum of 30 m or the distance determined by a Geotechnical Report.
Because a 30 m setback can severely limit the developable space, a Geotechnical Report is a simple way to expand the useable land on your property.
The Foothills County Land Use Bylaw also states that “If, in the opinion of the Approving Authority, a slope might be unstable, a geotechnical assessment by a professional engineer may be required in order to evaluate stability, and to recommend appropriate development setbacks, consistent with provincial guidelines”
Kneehill County
When applying for development in Kneehill County, the Area Structure Plans included in the application must provide “Geotechnical slope stability analysis of banks, slopes, and/or escarpments.”
When submitting a detailed engineering design, a Geotechnical Report may be required. If requested by the County as a condition of development, the Geotechnical Report must include top of bank setbacks adjacent to creeks or ravines with stability problems.
Vulcan County
When submitting a development application in Vulcan County, the Municipal Planning Commission may recommend that Council require the adoption of an area structure plan or design scheme which could include a Geotechnical Report to address slope stability.
Similarly, the use of land may be refused if, in the Development Authority’s opinion, the site of the proposed building is situated on an unstable slope. In this case, a slope stability assessment report by a qualified geotechnical engineer could be used to provide additional information and/or recommendations to stabilize the slope.
For hummocks, buttes, and other isolated land projections, slopes of greater than 20% are considered unsuitable for development unless otherwise determined. All slopes greater than 15% may require special engineering and other treatment.
Based on the Vulcan County Land Use Bylaw, the following conditions would apply to sloped land:
- Setbacks from toes of slopes shall be a minimum of 9.1 m (30 ft) from the toe of the slope
- parcel boundaries shall be setback a minimum of 9.1 m (30 ft) from the brink of a slope (front edge of a bench) when the height of a slope is greater than 3.0 m (10 ft)
- When the front edge of a bench is steeper than 33% and higher than 25 m (82 ft), the minimum setback from the point where the slope begins to fall off at a rate greater than 33% shall be one third the height of the slope
Wheatland County
When submitting a development application in Wheatland County, staff may require a shallow sub-surface geotechnical investigation and/or a slope stability report to support an Area Service Plan or concept plan. A setback of 30.48 m (100 ft) from the top or toe of the slope is required for development adjacent to a slope of 15% or greater.
In Wheatland County, the top of bank and toe of slope are defined by the transition to or from a grade of 15%. In general, the buildable area can not exceed 15% in slope unless deemed suitable for construction by a qualified professional. A Slope Stability Study, Slope Stability Analysis, or Geotechnical Slope Stability Report can be required at the discretion of a Development Officer
MD of Willow Creek
Within the MD of Willow Creek, the Subdivision Authority may require a development applicant to provide a slope stability report. Similar to other counties, when the development area includes land with a slope of 15% or greater, such a report may be requested.
Conclusion
Slope stability reports are often required in Alberta, and can usually be done for a reasonable price. Please contact us and we will be happy to help you out.
