Unpacking Trans Mountain’s “Credible Worst-Case” Oil Spill

This post is part of an ongoing series in which MLA Andrew Weaver will be sharing key information from inside the National Energy Board hearings on Kinder Morgan’s Trans Mountain pipeline proposal. To see previous posts, please click here. 

 Trans Mountain’s “Credible Worst-Case” Oil Spill

As part of their analysis, Trans Mountain conducted oil spill scenarios for what they consider to be “credible worst-case” and smaller-sized spills.

The purpose of running these scenarios is to estimate the likely impact a spill would have on our communities and our environment, as well as to gauge their ability to respond to a spill. The problem is, Trans Mountain’s “credible worst case” spill scenario only accounts for a small fraction of the oil that could actually spill.

Here’s what I mean:

A single oil tanker will carry over 110,000 tonnes of oil. Yet, according to Trans Mountain, the maximum size of a “credible worst case” spill (i.e. the largest spill they think could ever actually happen) would only be 16,500 tonnes. That’s only 15% of the oil carried by a single ship.

So where does their definition of a “credible worst case” spill come from?

Trans Mountain undertook a probability analysis, factoring tanker size, shipping lanes and traffic, as well as other data. They found that 90% of their spill scenarios were smaller than 16,500 tonnes in size. Trans Mountain then simply “defined” this to be their “credible worst-case” scenario. That is, they defined ‘credible worst-case’ as the 90th percentile.

That means there is not a single report or study in the entire 15,000 page application that considers what would happen if more than 15% of the oil on a tanker were to spill.

I found this profoundly troubling. In my first round of questions, I asked Trans Mountain to provide an analysis of the risks and impacts of having 100% of the oil spill. This is called a total loss scenario. While it fortunately isn’t a common scenario, it certainly does fall into the realm of possibility.

Unfortunately, Trans Mountain responded by saying that a total loss scenario was not “viable” or “credible”, that my request was therefore not relevant, and so refused to provide the sought after analysis.  They base this on the fact that “there has not been any total loss of containment scenarios involving a double hull tanker, ever, to date…”

The Problem with Trans Mountain’s “Credible Worst-Case”

I have two big concerns with Trans Mountain’s logic.

First, the very fact that Trans Mountain’s “credible worst case” oil spill only accounts for 90% of spills means that there is a 10% chance that an oil spill will be larger than their “credible worst case”. 10% isn’t some distant possibility—it’s a very plausible scenario.  In fact, the Exxon Valdez spilled roughly 35,000 tonnes of oil—more than double the size of Trans Mountain’s defined “credible worst-case” scenario. The Atlantic Empress released 287,000 tonnes of crude in 1979 after it caught fire and sank in the Caribbean. In 1983 Castillo de Bellver exploded off the coast of South Africa and released 50,000 to 60,000 tonnes of light crude into the sea. In 2002, Prestige split in half and sank off the coast of Spain releasing 63,000 tons. And of course, there are other examples. By refusing to even consider the possibility of these larger spills, they are ignoring spill scenarios that are certainly possible and that would have a devastating impact on our coast.

Second, while it may be true that so far no double-hull tanker has spilled 100% of its oil, this is far from a solid argument. The fact is, policies requiring all new tankers to be constructed with double-hulls are relatively new. It is only within the last 20 years that this has become a mandatory requirement. So, while a total loss incident involving a double-hull tanker has not occurred to date, these ships have not been in use long enough for such a justification to be made with much certainty.

This leads me to two basic questions:

How can Trans Mountain credibly say that they have provided a full analysis of the risks and impacts of marine oil spills, when they refuse to even consider the possibility of more than 15% of oil spilling?

How can British Columbians trust that Trans Mountain can actually clean up a spill, if the largest spill they are prepared for only accounts for a small fraction of the oil onboard?

If you ask me, they can’t.