Seismic Slope Stability Requirements in BC

As of February 1, 2010, the BC Building Code has been amended to require the consideration of potential for slope instability and it’s consequences at a building site becomes an explicit requirement in the design of structures and their foundations, additionally, the seismic design criteria has been increased to a probablility level of 2%-in-50 year. This will impact many developments across the provide, with geotechnical investigations to be required at almost all levels of development.

Below is the Information Bulletin from the Province on the matter.

APEGBC has issued a set of guidelines detailing the assessment, it is a 74 page PDF that may be useful for local authorities as well as geotechnical engineers, see below.

So what does this mean for the average house in BC? Well if you are in an earthquake prone area, the design requirements for slopes have been increased significantly. For other places in the province, with lower risk of earthquake, the requirements will most obviously have an impact on those areas with poor soils and steep slopes. At the moment there is not a lot of guidance out there on local tolerances and when building officials or approving officers should have concerns about meeting these requirements.

For my part as the City Engineer, I am aware of the requirements and have notified others in my organization as well, but the main point is that it is not possible to rely on common sense – just because someone wants to develop a lot and put a house there, doesn’t mean it is a good thing. If there is any potential for risk,  get a professional opinion in accordance with this Act.

Published by Mike Thomas

Mike Thomas P.Eng. ENV SP, is the author of and Director of Engineering at the City of Revelstoke in the Interior of British Columbia, Canada.

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