CAN/BNQ 2501-500/2017: Geotechnical Site Investigation for Buildings in Permafrost Regions

In 2017, the Standards Council of Canada (SCC) and the Bureau de normalisation du Québec (BNQ) announced the publication of a new National Standard of Canada (NSC) that will help ensure that infrastructure built in Canada’s North is adequately prepared for the uncertainties of a changing climate. CAN/BNQ 2501-500, Geotechnical Site Investigations for Building Foundations in Permafrost Zones, is the fifth standard developed through the Northern Infrastructure Standardization Initiative (NISI). It establishes a consistent methodology for performing geotechnical site investigations so that the results can be used to design building foundations with due consideration—in a risk management framework—of the conditions prevailing at the building site, including the distinctive characteristics of permafrost and the seasonal and interannual climate conditions as well as the projected climate conditions over the service life of the building foundations. In the long term, it is expected that this standard will help reduce maintenance issues which, as a result of climate change or improper site evaluation, can cause permanent damage to structures. NISI standards address the unique circumstances found in Canada’s North, providing mechanisms to help adapt and reduce the vulnerability of northern infrastructure to the impacts of climate change. Building on the success of Phase I of NISI, SCC has embarked on a second phase that will continue to address critical issues relevant to Canada’s North amidst a changing climate. Taken together, these standards will help building owners and operators and those responsible for public and community infrastructure build and maintain resilient infrastructure in a changing climate. By engaging communities and experts from across the North, SCC is providing standardization solutions that are effective in addressing climate change impacts to northern infrastructure, planning and management. In the process, we are helping to protect the health and well-being of Canadians, communities and the economy.

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Understanding and Assessing Impacts

Over the past decades, from 1961-2010, the North warmed more than any other region in Canada and more than most regions on Earth. Recent studies show that much of the warming has occurred since the 1970s with the most recent climate change models projecting ongoing or accelerating climate changes into the future. This warming climate is modifying the ground thermal regime and changing the properties of permafrost. Permafrost in many areas is beginning to thaw and the active layer of the ground, which freezes and unfreezes every year, is deepening as ground and air temperatures warm. This results in unreliable soil conditions and failures in construction. Although there wasn’t one specific event that led to the development of the standard, there have been a series of infrastructure issues in the North that have occurred over the years. For instance, there was a school in Yukon that experienced issues with major pieces of infrastructure failing soon after it was established due to an inadequate characterization of permafrost. This established the need to be systematic when assessing permafrost risk throughout all stages of infrastructure lifecycle from planning to design and construction. Although there wasn’t any specific climate data sets or projections used in developing the standard, the World Federation of Engineering Organization (WFEO)’s Model Code of Practice: Principles of Climate Change Adaptation for Engineers as used to inform and provide guidance in considering the impacts of a changing climate on infrastructure and buildings. This guideline was derived from a guidance prepared by Engineers Canada and both documents recognize that access to appropriate information on weather, climate and climate change is key and that engineers should work collaboratively with and climate/weather specialist to identify the types of climate design data needed for the issue.

Identifying Actions

The Standards Council of Canada (SCC) is a Crown corporation and part of the Innovation, Science and Economic Development Canada portfolio that leads and facilitates the development and use of national and international standards and accreditation services in order to enhance Canada’s competitiveness and well-being. Since 2011, SCC has been working with communities, standards development organizations, and experts from across northern Canada to support the development of standards that consider climate change impacts in northern infrastructure design, planning and management. These standards – developed under the Northern Infrastructure Standardization Initiative (NISI) – help building owners and operators, as well as those responsible for public and community infrastructure, build and maintain infrastructure in a changing climate. CAN/BNQ 2501-500, Geotechnical Site Investigations for Building Foundations in Permafrost Zones, is the fifth standard developed through the NISI. The development process involved expert solicitations that were carried out through interviews conducted with key informants, practitioners and important client groups that would commission work for the development of infrastructure in permafrost areas. The issue of unstable permafrost zones was highlighted in these discussions with questions such as:

  • When developing infrastructure through continuous or intermittent permafrost, how do you make decisions regarding how to go about the geotechnical investigation?
  • How spatially and temporally varied should these investigations be to increase accuracy?
  • How many core samples is enough for proper due diligence in terms of understanding how much permafrost and what kind is here.

After these discussions, a request for proposal (RFP) was issued for standards development organizations and Bureau de normalisation du Québec (BNQ), a standards development organization accredited by SCC, was selected in February 2015 to develop the standard.

Implementation

CAN/BNQ 2501-500/2017: Geotechnical Site Investigation for Building Foundations in Permafrost Zones was published in February of 2017 as a new National Standard of Canada (NSC). This standard applies to the measuring of site-specific conditions in the process of performing geotechnical site investigations. The principles laid out in this standard are specific to geotechnical site investigations performed to support the design of building foundations. They may apply to other types of infrastructure located in permafrost zones. It is the user’s responsibility to judge the suitability of this document in these cases. This standard is primarily aimed at geotechnical consultants. It is also intended to be used by the owners of buildings, designers of buildings, contractors and regulators. This standard was developed to establish a consistent methodology for geotechnical site investigations which includes, data collection and evaluation, reporting for site conditions while accounting for seasonal and interannual climate conditions as well as the projected climate conditions over the foundation’s service life. It was developed with the view that the geotechnical site investigation should provide the information that will allow for the design and maintenance of a building within a reasonable timeframe and cost while taking into account the specific constraints of the North and the diverse nature of building projects. Each project is carried out within a risk management framework that assigns risk levels based on the sensitivity of the permafrost to climate change and the consequence of failure for the building’s foundations. The level of geotechnical site investigation will depend on this sensitivity with higher investigations for moderate to high-risk projects and lower investigations for low-risk projects.

Outcomes and Monitoring Process

Full lifecycle management of infrastructure in the North requires a comprehensive understanding of the unique challenges and risks arising from the North’s harsh climatic conditions. The fourth edition, March 2021 of the Good Building Practice for Northern Facilities highlights the complexities that may be encountered when planning, designing, constructing, and maintaining infrastructure in remote, cold regions. The aim of this design guide is to present a compilation of best practice recommendations learned over many decades of cold region experience while incorporating modern and effective technologies and methods involving all aspects of northern infrastructure. The design guide outlines new codes and standards and includes new sections on environmental regulations; climate change; hazardous building material assessments; and civil, environmental, and geotechnical considerations. The BNQ standard was included as the Site Characterization chapter of this document guide under “Geotechnical Evaluation.” This demonstrates the use of this standard to perform:
  • A Preliminary Site Evaluation: This is based on a review and interpretation of available information, such as previous geotechnical reports from the same area, geological publications, air photo and satellite imagery, and Environment Canada climate data. The objectives are to characterize the geotechnical, hydrological and climatic conditions of the site.
  • A Site Investigation: involves some form of subsurface investigation to identify the extent, characteristics and properties of unfrozen and frozen soil and bedrock; the presence of ground ice; the presence of groundwater; and the ground thermal regime of the building site.
It is important to note that this standard does not apply to post-construction monitoring of the building site conditions, which is covered in a different standard document CAN/CSA-S501: Moderating the effects of permafrost degradation on existing building foundations.

Next Steps

Climate change is continuing to impact northern communities, and communities need tools to adapt. To date, thirteen standards and technical guides have been funded under NISI to support building in permafrost, dealing with extreme weather (like high winds), design with climate change and risk in mind, and to support the design of community systems like solid waste sites and drainage systems. NISI provides practical, on-the-ground solutions that are written by experts in the field and specifically geared for the north. The standards have been written to recognize the geographic isolation, climatically hash nature of the region, and the need for efficiency and resiliency. Once new standards are published, SCC works with its project partners to provide in-class training, free of charge, easy-to-understand guides, and online training modules such as webinars to introduce northerners to the standards.

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