Mark Hume, The Globe and Mail, Jul. 15 2012
When pipelines rupture, it usually takes hours before the flow of oil is shut off.
Why? Obviously, an instant response to a pipeline leak would minimize the environmental impact and be less expensive to clean up. But could it be that pipeline transportation technology, as modern and high-tech as it is, simply can’t respond quickly enough?
In Michigan, in 2010, it took 17 hours and 19 minutes for Enbridge Inc. to realize its pipeline was gushing bitumen into the Kalamazoo River. That delay allowed three million litres to escape and later drew the condemnation of the U.S. National Transportation Safety Board.
When a Plains Midstream Canada pipeline ruptured in Alberta in June, 3,000 barrels of oil had leaked into the Red Deer River before the company shut down a 10-kilometre section of line and began the messy cleanup.
In 2000, 6,200 barrels of light crude escaped into the Pine River in northeast British Columbia when a Pembina Pipeline Corp. line broke open, causing the worst inland oil spill in the province’s history.
Pipeline companies obviously want to turn the shut-off valves as quickly as possible when pipelines fail, because the cleanups are immensely costly. Pembina had to spend more than $30-million to mop up the Pine River, and Enbridge is looking at a $765-million bill for the Kalamazoo disaster.
But delays occur because the companies are monitoring lines with computer systems that sometimes miss warning signs, and because the very nature of pipelines means an abrupt shutdown often just isn’t possible.
A federal official who has investigated major pipeline oil spills in Canada – and who won’t be named because he spoke without getting approval from media handlers in Ottawa – says those problems are especially challenging in British Columbia.
“In B.C., the hilly terrain presents a lot of difficult technical issues due to pressures in the line,” he says. “When shutting down a line, especially in B.C., there is usually a very difficult technical problem related to a pressure phenomenon which in hydraulic engineering is commonly called ‘water hammer.’ It is the same thing that happens in your house when you quickly shut off the water and you hear a bang. In pipelines, you have a massive quantity of liquid moving in one direction which has tremendous momentum. If you shut down the pipeline quickly, that momentum creates … tremendous pressure against the valves and the anchoring system of the pipeline. It’s like running the 100-yard dash toward an open door when someone slams it shut just before you get to it. All your forward momentum creates quite a bang when you hit the door. If valves are shut too quickly, the momentum force of the oil can blow out the valve, rupture the pipe or literally rip it off its mounting foundations and destroy the pipe.”
This means that, even when they are responding to a spill correctly, pipeline officials often cannot rapidly shut down a ruptured line because the water-hammer problem might cause more damage.
That’s not the only difficulty in crossing mountainous B.C.
“In hilly terrain, there is also the danger of siphoning. The momentum of the oil on the downhill slope can pull the oil in the previous uphill slope up over the hill and down the other side, similar to siphoning gas out of a car’s gas tank. This increases the amount of oil spilled out of the break. This can also confuse the [computer control] system,” he says.
The computer monitoring system, he explains, measures the flow between two points – for example, two valves on either side of a hill. If a rupture occurs between those valves, and siphoning starts, the computer won’t immediately detect the leak, because oil is still flowing past both valves. So the oil company unwittingly pumps more oil down the ruptured line and out the crack.
This is why little leaks sometimes turn into big spills, even though the pipeline companies are doing everything they can to prevent that from happening. And it is why British Columbians are nervous about Enbridge’s proposed Northern Gateway line, which will have to cross some of the most mountainous terrain and richest salmon rivers in Canada.