With our population growing and city planners promoting increased urban density, developers are being encouraged to construct housing on marginal lands. In some cases, this can increase the potential for land slippage. Over the last few years, there have been significant landslides in residential areas all over British Columbia. They have occurred in North Vancouver, Qualicum Beach on Vancouver Island and in many towns in the interior, such as Vernon, Kamloops, Penticton, Oliver and, most recently, Pemberton.
On February 1, 2010, the Government of British Columbia enacted amendments to the British Columbia Building Code that specifically address slope instability. It is now a mandatory requirement that the potential for slope instability, and its consequences such as a landslide, be considered and taken into account when designing buildings and their foundations. The amendments also set the standard to be utilized for the purpose of assessing slope instability at a probability of 2%-in-50 years, which is down from the 10%-in-50 year standard contained in preceding interim legislation.
Despite this new legislation, landslides will continue to be an unavoidable reality given the sloping terrain of the most heavily populated areas of B.C. Landslides, like any other natural disaster with the potential to cause injury to people and damage to property, expose many different groups to legal liability for what can often be very significant losses. The groups with the greatest exposure to liability from landslides are: local governments, engineers and property owners.
Local governments are often the party most directly involved in landslide-related litigation because of their role as the permitting authority. Permits are required for any type of construction and specific measures or assessments will often need to be undertaken before allowing construction on sloped or unstable land. Potential liability arises primarily from improperly allowing construction on unstable land or for failing to warn of instability by disclosing information concerning risks associated with a particular property or area.
The Province has assisted local governments by enacting legislation that authorizes them to require landslide assessments in connection with each stage of the development process — subdivision approval, development permit, and building permit. If a professional engineer certifies that the plans or design for construction comply with the building codes or bylaws (including guidelines for slopes), a local government may rely on that certification for issuing a permit. In such instances, the local government may avoid legal liability for having issued a permit that did not meet the Code’s requirements.
The legislation also allows a local government to require an owner to carry out particular measures to preserve or improve slope stability, as a condition of granting a permit. It may also require, as a warning for subsequent owners of a property, that any identified concerns about ground conditions be noted on the title for that property.
Engineers who are engaged to assess the viability and safety of a proposed development or construction will often be required to consider the suitability of the site and the stability of the ground. All practicing engineers have significant exposure to claims but, in our experience, geotechnical engineering is a particularly high-risk area. The stability of a slope cannot be measured precisely since it is dependent on a variety of factors and assumptions and influenced by unknown factors such as weather. Also, the ground conditions and surrounding factors that affect a slope’s stability invariably change over time. An assessment completed for permit purposes 20 years ago may not identify or address the hazard that could lead to a landslide now.
As in all areas of professional practice, the standard by which the engineer’s performance will be measured is that of the reasonable level of performance of an appropriately qualified and experienced engineer in similar circumstances. In this particular area of practice, the standard for measuring an engineer’s performance will likely be established, to a large degree, by the Guidelines for Legislated Landslide Assessments for Proposed Residential Development in British Columbia. These were first published by the Association of Professional Engineers and Geoscientists of B.C. or APEGBC (the body that regulates the practice of engineers in the province) in 2006 and revised in 2008.
The Guidelines establish a framework within which engineers can work when called upon by their clients to assess whether a proposed site can be safely used for building. By identifying factors to be addressed as well as recommending specific approaches for carrying out the assessment and reporting to clients, the Guidelines should result in a more uniform approach to assessing slope stability to the benefit of the engineers providing the service and to their clients. There is also a form, the “Landslide Assessment Assurance Statement”, attached to the Guidelines. After completing an assessment, this form can be submitted to a local government as the engineer’s professional assurance on slope stability. This statement enables a developer, contractor or other party to obtain a development or building permit. (The Guidelines are an essential tool for any engineer involved in assessing ground conditions and are available at the APEGBC website at www.apeg.bc.ca.)
Liability for property owners can arise if they fail to take reasonable measures to eliminate or reduce known hazards on their property such as slope instability (see Letter of the Law, Summer 2006). For example, an owner who removes trees and other vegetation from a steep slope or builds a retaining wall without provision for drainage could be held liable for the damage caused by a subsequent landslide. It is worth noting that owners can be liable in nuisance for damage caused by slides which originate from their property even if they are completely unaware of instability on their property.
Because liability in nuisance is “strict”, it can be imposed without direct knowledge of the hazard or fault and, in many cases, it will be no defence for the property owner to say that they could not have known that their actions, or inaction, would cause or contribute to a landslide. Owners of any sloping property should consider obtaining an assessment from a geotechnical engineer, particularly before beginning any construction on the property or changes to grade or drainage. All property owners should also maintain liability coverage on their home insurance policy and discuss with their broker what level of coverage might be appropriate for their property.