Leaks have been a frequent occurrence in the Keystone Pipeline in recent years. Two years ago, 407,000 gallons of oil spilled onto farmland in northeastern South Dakota. The company initially reported the spill at around half that size.

Bad quality control and a rush to complete construction. Typical American way of doing these things unfortunately. Even with their own very stringent engineering codes this still happens far too often simply because of the pressure to "git 'er done!" ahead of schedule. The last leak I heard about was caused by a couple of welders using the wrong electrodes because they'd run out of the approved ones and didn't get more of them because (a) they were too scared of getting fired by their angry supervisor, or (b) they were just too lazy to take the time to go get the correct ones. Weld pops open a year later, farmer's land gets contaminated beyond recovery, and the pipeline owner ends up in hock for multi-millions of dollars for both the repair and the legal liabilities. No one wins at all from this but it keeps happening over and over again just because some asshole desperate for an early-completion bonus in a head office somewhere is in a hurry during construction.

Not a cheap shot at the US, but this happens far more often there than it does in Canada. American executives and site superintendents tend to have a Third World attitude, as shown by the BP Horizon offshore rig disaster, where all they care about is maintaining an increased speed of production. That they're deliberately increasing the odds of accidents and failures simply doesn't enter their minds. That there's also so little on-site observation and inspection by state or federal government inspectors just makes it that much worse.