There are many things that human aren't very good at doing.
One of them is assessing "risk".
There are a number of reasons for this. Mostly it is because we don't really know all of the variables involved for any given situation but it is also because it is human nature to over- or under-estimate risk based on the immediate circumstances.
Take 9/11 as an example.
If you had asked anyone, anywhere, on Sept. 10, 2001, what are the chances of two planes being hijacked and flown in the World Trade Center, they would likely have responded that the risk is miniscule. Add that two more planes would be flown, on the same day, into the Pentagon and towards the Capitol building and they might have laughed at the suggestion.
Yet, on Sept. 11, 2001, that is exactly what happened.
Since then we have lived in a state of heightened tension with airport security being pushed to absurd levels. Why? Because we underestimated the risk of such an attack before it occurred and we are now, to be safe, overestimating the likelihood of such an attack occurring again.
But was the risk really underestimated?
How do you go about calculating such as risk in the first place?
This is not a trivial question. Calculating risk is a very hard thing to do. Much effort has gone into developing the field over the past forty years.
Risk analysis has been applied to various industries such as chemical plants, pulp mills, and refineries. In these cases, the driving force is an effort to create a safer work environment. Ideally, it is to make industrial processes foolproof thereby preventing any accidents.
Of course, as Douglas Adams once said, "A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools."
The reality is that there is no such thing as a risk free activity. The act of living is inherently a risky proposition. It is all a question of what risks are we aware of and how much risk are we willing to take?
For example, would you jump out of a plane without a parachute?
Your gut response might be "no". It certainly sounds like a risky proposition. But doesn't it really depend on a variety of factors such as whether or not the plane is on the ground, what type of plane it is, and what other circumstances are involved?
People have survived tremendously long falls from planes. Personally, I just wouldn't bet my life on doing so.
Still, I am quite willing to fly even though I don't have a parachute to save me. I know that the risk of an accident is very small. Just consider the number of passenger miles flown each year compared to the number of fatalities. Flying is about as foolproof a method of travel as possible.
A more immediate concern, though, is how do you assess the risk of a pipeline leaking?
One of my students suggested "you guess". Enbridge has come up with a figure of once in 15,000 years. A miniscule risk it would seem.
But where does that calculation come from?
I would suggest that a little research might give us a better estimate of the likelihood of both the frequency and the extent of leaks if the Northern Gateway Pipeline is built.
According to Enbridge's own website, they operate 24,613 kilometres of crude pipeline.
According to the Polaris Institute, between 1999 and 2010, Enbridge experienced 804 spills (or leaks) releasing a total of 168,645 barrels of crude oil. On average, that is 210 barrels per spill or about 33,000 litres.
Put another way, 804 spills over 12 years on 24,613 kilometres of pipeline means that Enbridge typically has 1 spill every year for every 367 kilometres of pipeline that they operate.
Northern Gateway is two pipelines with a total length of 2,354 kilometres so we can expect about 6.4 spills per year averaging around 33,000 litres each.
One could make the argument that these are small spills, not significant, and the risk associated with the pipeline is low. Maybe so.
But during the past 10 years, Enbridge has had eight major spills - each releasing over 500,000 litres of crude oil. That is, 0.8 spills per year on average for 24,613 kilometres of pipeline or 1 major spill of every 30,766 kilometre/years of pipeline operation.
Northern Gateway is proposed to have a 30 year life span or 70,620 kilometre/years of operation. This simple risk analysis would suggest that the likelihood that the pipeline will have a major spill during its lifetime is pretty good. Indeed, the numbers would suggest that two such spills should be expected.
Of course, there are all sorts of new technologies being applied to pipelines in order to reduce spills and leaks - to make their operation foolproof.
But in that regard, just remember what Douglas Adams said.
