Gas explosions rare, but danger always present, Canadian experts say after Boston area blasts

A chain gas explosion similar to the one that tore through three Boston suburbs could happen in Canada, although such a possibility is unlikely, energy experts said Friday.

The multiple explosions that caused more than 20 fires and at least one death in Boston on Thursday are "very rare,'' said the director of the Queen's Institute for Energy and Environmental Policy, in an email.

Warren Mabee said while the cause of the explosions in Boston is still unconfirmed, it appears the gas-distribution system became over-pressurized during repair work, causing gas to leak into multiple buildings and ignite.

He said most gas networks have alarms that trigger the distribution system to shut down before pressure builds, although it's unclear why those didn't work in this case.

"There are a lot of safeties built into the gas-distribution system,'' he wrote.

"I can only speculate as to why they didn't work in this case, but it may have had something to do with the upgrade that was being done.''
  
While the Massachusetts explosion may be unique due to the sheer volume of buildings affected, Canada is not immune to such tragedies.

In Ontario alone, there have been 179 natural gas explosions and two fatalities in the last 11 years, according to the province's safety regulator.

Those numbers, which do not include incidents caused by homicides and suicides, include 79 explosions at private dwellings.

The figures also do not include a tragic incident that occurred in 2003, when seven people died when an explosion levelled a strip mall in the Toronto neighbourhood of Etobicoke.

Enbridge Gas Distribution Inc. and several other companies were fined hundreds of thousands of dollars in the aftermath of the explosion, which was caused by a backhoe hitting a gas line.

But, Mabee says even that incident did not cause the kind of chain event seen in Boston, ``because there wasn't any kind of overload on the system,'' he wrote.

About 35 per cent of Canada's energy needs are met with natural gas, according to the website of the Canadian gas association.

The association declined an interview request, but said in a statement it was monitoring the situation in Massachusetts and had offered to provide aid if required.

"We will be working with our U.S. colleagues to learn as much as possible about what has happened and how to prevent such incidents,'' the statement read.

A spokesperson for Quebec-based natural gas company Energir, which serves nearly 205,000 customers, said she doubts a similar tragedy would occur in Canada, but it's impossible to say without knowing what caused the blasts.

"The same natural gas runs our pipes as it does in Boston,'' Catherine Houde said in a phone interview.

"However, we do not do maintenance work the same way, our network is also younger, and we don't have the same measures put in place.''

Houde said her company uses different materials in its pipes than Boston does, and has many safeguards in place to prevent and respond to breaks and pressure buildups.

Safeguards include testing pipes to handle much higher pressure than they're expected to carry, 24/7 monitoring, and pressure release valves that automatically go off when anything abnormal is detected.

The company deals with about 500 gas leaks per year, almost all of them caused by construction crews breaching pipes, she said.

Despite that, she says there hasn't been a major incident since 2005, when a fire and explosion killed one person in Pointe-du-Lac, about halfway between Montreal and Quebec City.

But, Houde said there's always a danger when dealing with natural gas and the company will follow the aftermath of the Boston incident to learn more about what happened and how so many houses could have been affected at once.

"Honestly, we don't know how something like that could have happened,'' she said. "We wouldn't have thought it was possible.''


With files from The Associated Press