INNOVATION September-October 2012

Brian Gunn PEng is a professional engineer with experience in construction supervision and project management both in Canada and overseas. Dr Ricardo O Foschi PEng is Emeritus Professor of Civil Engineering at the University of British Columbia, specializing in probabilistic methods in engineering, including reliability and performance-based design under reliability constraints, particularly in earthquake engineering. Dr Robert G Sexsmith PEng is Emeritus Professor of Civil Engineering at the University of British Columbia, specializing in probabilistic risk/safety and decisions for structural safety. His work has included consulting engineering for bridge design and erection, and ship collision risk assessment.

those normally required in the design of important civil infrastructure. For example, the Enbridge study estimates a return period of just 78 years for a spill of any size if no tugs are used, and 250 years if navigation is assisted by tugs. These return periods increase, respectively, to 200 and 550 years for substantial spills greater than 5,000 m 3 . The use of return periods does not provide a complete picture of the risk involved: we believe that it is more important to provide the probability that there will be at least one spill during the 50-year lifetime of the project. There is a mathematical relationship between this probability and the associated return period. Thus, the probability (in percent) associated with a return period of 78 years is 47%, for 250 years is 18%, for 200 years is 22% and for 550 years is 9%. It is our belief that these probabilities are too high and represent an unacceptable level of risk. It seems incongruous that British Columbians should accept these risks while, at the same time, demanding a design target probability of 1.0 x 10 -4 (a 10,000 year return period) for a Class 1 bridge collapse due to ship collision (as in Canadian and US Bridge design codes), or using a return period of nearly 2,500 years for a design earthquake. Risk is not only probabilities but involves the corresponding consequences, and the very high consequences from spills demand much lower probabilities or much longer return periods. The Enbridge study does not consider the increase in traffic due to LNG tankers, which would further reduce the return periods and increase the associated probabilities. The question remains as to whether the return periods estimated by the Enbridge study are themselves reliable, given the inherent uncertainties when using different calculation models. To assess this question, we considered two different, independent, alternative calculation approaches. These are described in detail in our submission to the Joint Review Panel of the National Energy Board (https://www.neb-one.gc.ca/ll-eng/ livelink.exe?func=ll&objId=847750&objAction=browse) In our study we considered, separately, incidents of groundings and then collisions with other tankers. We obtained, for example, a return period of 81 years for an incident of grounding and 73 years for tanker collisions. These results imply a return period of 38 years for incidents either from groundings or from collisions (resulting in a 73% probability of at least one such incident in a 50-year life for the project). Thus, our results agree with the Enbridge study in that our estimates are also very short, and find that they imply unacceptably high associated risks. Our conclusion is then that tanker shipping of bitumen from Kitimat is too risky and should not be approved. Furthermore, our group believes that the impact of bitumen spills would be catastrophic for: • First Nation food supply and their culture; • Nature and adventure-based tourism operations; • Commercial fishery; • The environment; and • Safety of humans and wildlife in the vicinity of the spill area. For these reasons, we believe that bitumen should not be shipped as proposed by Enbridge. We further encourage all our fellow professionals to read the different reports presented to the Joint Review Panel of the National Energy Board, and to consider this very important issue for the welfare of our province and to join a reasoned discussion of the proposal. v

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