Raphael Lopoukhine. North Shore News. North Vancouver, B.C.: Dec 9, 2007. p. 5

NV task force assessing 'tolerable risk'

If your house had a one in 10,000 chance of being crushed by a mudslide would you want it regulated and fixed, but what about if the ratio was one in 15,000 or 20,000? Quantifying what constitutes a tolerable risk is not easy. Any tolerable risk ratio is sure to draw criticism as too high by some or not high enough by others. Nevertheless, it’s a question that the District of North Vancouver Natural Hazards Task Force must answer.

The task force compromised of volunteers, both from technical and lay backgrounds, held a public meeting Dec. 4 to present their preliminary findings of what they believe constitutes a tolerable risk to the general public.

The task force proposed, based on previous examples, meetings with experts and public input that the level of tolerable risk for new developments should be a 1 in 100,000 chance of death per year from natural hazards, but for existing developments the ratio should be much less with a 1 in 10,000 risk of death.

“The reason we agreed to that is that when those properties were built, we didn’t know a lot about this, we didn’t know about the hazards, so it would not be fair for those people who already have those houses built to have to rebuild or retrofit their houses to a different standard,” said task force member and city of Coquitlam emergency programs manager Dorit Mason. “However, when a brand new building is being built, having a higher risk tolerance seems reasonable.”

The crowd of about 20 was a mix of concerned residents either already assessed as having some risk associated with their home or believes they are at risk based on their own observations. Many attendees were equipped with pens and paper and furiously scribbled notes throughout the presentation.
The difficulty associated with assigning risk a numerical value came to light with the examples of two residents in opposite situations, but on this night sitting next to each other.

Lesley Brooks from Browning Place lives right next to an escarpment in a house built over fourty years ago. If her home is assessed to cause a threat down below, based on the numerical threshold, she may be forced to make changes – expensive changes. On the other hand, Sandra Seres lives on Riverside Drive below a home that has already been assessed to have a risk above the one in 10,000 threshold, but not by much. Therefore, the resident up above would have no legal obligation to act.

“I would like to have less risk, but I am at the bottom of the slope,” said Seres who wants a mediation process established by the district to handle situations like hers. She said she just wants her risk reduced and is willing to work pragmatically to achieve that end. She is hopeful that the district will initiate a constructive process.

The district’s director of environment, parks and engineering services Jozsef Dioszeghy admitted the district “didn’t pay a lot of attention to natural hazards for a relatively long period of time.”

After the January 2005 landslide on the Berkley escarpment that left one person dead and another critically injured, the district’s response is now a leading Canadian example, task force members say.

“There is huge interest all over Canada what is happening here, I hear that from colleagues, I hear that from other jurisdictions, and other potential clients,” said BGC engineer Matthias Jakob. “They are all watching very carefully and they like to look at the DNV as a bit of guinea pig.”

Interjecting right after Jakob, Mason added: “And I think the emergency management field as well, the emergency managers are also watching this process.”

The task force has been studying the issue for 6 weeks, taking part in 5 meetings, involving 4 discussions with experts. They’ve held one open house, conducted a survey and now the public meeting. They’ve had 62 residents complete the survey and welcome more input. (The survey is available online at dnv.org.) The task force will be presenting their findings to the district council in early 2008 and their findings will most likely have regulatory impact on existing developments and future permits. In the interim, the district has used the 1 in 10,000 ratio as the threshold for tolerable risk.