Preface

This is the first edition of CAN/CSA-S501, Moderating the effects of permafrost degradation on existing building foundations.

This Standard has been developed through the collaboration of representatives from territorial governments, the federal government, universities, the private sector, and northern community government organizations.

Photographs and figures without sources in the document were supplied by Steven Kokelj, Antoni Lewkowicz, Richard Trimble, John Watson, and Stephen Wolfe.

CSA Group received funding for the development of this Standard from Standards Council of Canada, as part of the Northern Infrastructure Standardization Initiative, supported by the Government of Canada's Clean Air Agenda.

This Standard was prepared by the Working Group on Permafrost Degradation, under the jurisdiction of the Technical Committee on Northern Built Infrastructure and the Strategic Steering Committee on Construction and Civil Infrastructure, and has formally been approved by the Technical Committee.

This Standard has been approved as a National Standard of Canada by the Standards Council of Canada.

Introduction

Permafrost degradation can be caused by many factors. When degradation occurs, buildings or structures constructed on permafrost can suffer distress or damage.

This Standard is organized according to the progression of steps that should be undertaken in order to moderate the effects of permafrost degradation on existing buildings or structures:

a) pre-emptive and proactive measures to maintain permafrost beneath and adjacent to existing buildings or structures;

b) assessment of structures impacted by changing permafrost conditions. This includes the following steps:

i) distinguishing the symptoms of building or structure distress related to permafrost degradation from those related to seasonal frost movements;

ii) investigating the site and structure conditions;

iii) establishing a monitoring program; and

iv) producing a final evaluation report that outlines alternative mitigative measures for the structure, recommendations for implementation of the appropriate mitigative measures; and the development of an implementation plan;

c) mitigating permafrost degradation and its effects on existing buildings and structures, as appropriate; and

d) undertaking long-term maintenance and monitoring.

The strategies available to moderate the effects of permafrost degradation on existing buildings or structures depend on site-specific conditions. The use of this Standard therefore requires a flexible approach.

Scope

1.1 Mitigation techniques and other actions

This Standard covers the following mitigation techniques to maintain permafrost or remediate permafrost degradation around existing buildings or structures:

a) site techniques that consist of

i) shading;

ii) drainage and grading; and

iii) ground cover and snow management;

b) foundation techniques that consist of

i) ventilation;

ii) insulation;

iii) mechanized refrigeration;

iv) thermosyphons; and

v) foundation replacement;

The Standard also covers site abandonment or structure demolition in response to permafrost degradation.

1.2 Applicable foundation types

This Standard covers the following foundation types typically constructed in permafrost terrain:

a) shallow foundations:

i) footings supported at the ground surface, with a ventilated air space under the building or structure;

ii) buried footings, with a ventilated air space under the building or structure; and

iii) slab-on-grade with no air space under the building or structure.

b) deep foundations:

i) adfreeze piles, with a ventilated air space under the building or structure; or

ii) rock socket or end-bearing piles, which may or may not have a ventilated air space under the building or structure.

Note: Further information on these foundation types is presented in Annex A.

1.3 Application

This Standard is intended to be used by the following:

a) the owners and operators of buildings or structures that can be affected by the degradation of permafrost;

b) the owners and operators of other community infrastructure (e.g., drainage systems) for which the maintenance of permafrost or remediation of permafrost degradation is important;

c) building contractors who implement engineering-based interventions;

d) design professionals and reviewers (consulting engineers, architects, and territorial or regional technical services staff) who design, assess and approve, and oversee the implementation of engineering-based interventions;

e) educators, for the purposes of knowledge transfer; and

f) regulators, such as building inspectors.

1.4 Terminology

In this Standard, "shall" is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; "should" is used to express a recommendation or that which is advised but not required; and "may" is used to express an option or that which is permissible within the limits of the standard.

Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material.

Notes to tables and figures are considered part of the table or figure and may be written as requirements.

Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application.