Dr. Gerald Graham's Letter of Comment to Enbridge Northern Gateway Project Joint Review Panel
In the Marine Shipping Quantitative Risk Analysis ( QRA ) Enbridge submitted in support of its application for approval, terminology is used that even a highly educated lay person would find hard to understand. Thus, the QRA talks of “return periods” for spills, rather than probabilities, chances or odds. Similarly, it measures the amounts of oil potentially spilled in cubic meters ( m3 ) rather than barrels, which is the way most people think of oil spills, if they ever do think of them.
A case in point is Enbridge’s calculations for a “major” or “extremely large” spill which they define as a tanker spill of 40,000 m3 or greater ( >40,000 m3 ). The company estimates the return period for this category of spill, with return period basically defined as the period within which one can expect at least one such spill to occur, at roughly 15,000 years.
Applying a formula for converting return periods into probabilities that was developed by Professor Shane Rollans, a Mathematics professor, for Mr. Kelly Marsh, and relying on calculations that were made, using that formula, by Professor Shane Rollans and Dr. Tom Haslam-Jones, a tanker spill of >40,000 m3 with a return period of 15,000 years translates, in layman’s terms, into a .3% chance of at least one spill greater than c. 252,000 barrels occurring over the fifty year lifespan of the project. So, not much chance of that happening, if Northern Gateway’s estimates are accurate. For the record, that's about the same size spill as the Exxon Valdez incident in Alaska in 1989.
But the risks are significantly higher for some of the other spill ranges for which Enbridge provides calculations; for instance, spills <5000 m3, and spills >5000 m3. The estimated return periods for these types of spill are 570 and 550 years respectively. Put these into layman’s terms, and there is a 10.0% chance that at least one spill under 31,500 barrels will occur, plus an 8.7 % chance of at least one spill over 31,500 barrels. All told, there is an 18.1% chance that at least one spill of any size will occur.
Moreover, if the pipeline is expanded from the outset to 850,000 barrels per day capacity, as Enbridge has indicated it could be, up from the 525,000 barrels per day capacity that the company is currently applying for, then, et ceteris paribus, the chances that at least one spill <31,500 barrels and at least one spill >31,500 barrels will occur increase by sixty two percent each- to 16.2% and 14.1% respectively. That's as much as a one in six chance of at least one potentially significant size spill occurring. Plus, at that higher throughput, the chance of at least one spill of any size occurring rises to 29.3%.
This will seem like an acceptable level of risk to some observers, while others will view the marine transportation component of the project as little more than a crapshoot. At the very least, it undermines Enbridge's assertion that a tanker spill is "...very unlikely to occur", and a similar assertion by the President and CEO of the Pacific Pilotage Authority that the chances of such a spill are "...extremely small". And now, thanks to the work of Shane Rollans, Kelly Marsh, Tom Haslam-Jones and myself, a lay person should be in a better position to visualize these risks, before making an informed decision as to whether the project should go ahead. Because if the Joint Review Panel currently reviewing the application had only one factor it could consider in making a go/no go decision vis a vis this project, that factor would undoubtedly be risk; everything else is secondary.
Gerald Graham, Ph. D