The Enbridge pipeline people have tried to assure people who live along the route of their proposed oil sands pipeline or the tanker routes along the BC coast, that modern science makes a leak almost impossible. This is Titanic think. What they mean is, if an untoward event such as an earthquake, deep freeze, storm etc. that they anticipated happens, the pipeline will hold up if it were build perfectly to spec, by a contractor who took no shortcuts and substituted no inferior materials.
If those condition do not apply, e.g. if the earthquake is one notch larger than built for, all bets are off. Designers may fail to consider what will happen if an angry farmer take pot shots at the pipeline with a rifle or some terrorist decides to blow it up, or a runaway tractor smashes into it, or a horny moose is attracted to its warmth. Only a tiny core of tidy problems are considered in the computer simulations.
If this degree of safety were attainable, we should not have seen any leaks or tanker spills in the last five years or so. But we have, on 2012-06-07, 3,500 barrels of light sour crude oil were released into Jackson Creek, a tributary of the Red Deer River north west of Calgary Alberta.
I wrote the computer program that designed BC Hydro’s high voltage transmission lines. Before you start, you have to decide what are the worst case conditions you will build for. Then you seek out the cheapest design that will survive them. You close your eyes to what will happen if the wind is 20% bigger or the ice is 10% heavier than you planned for.~ Roedy (1948-02-04 age:70)