For a look at risk assessment and several descriptions of possible consequences of a rupture of the PNGTS Extension, read Dr. Alp's presentation during environmental hearings on TQM's project.
In more simple terms, here's what municipal officials were told by TQM safety experts about the consequences of a rupture on the TQM high-pressure pipeline.
"Like ground zero at a nuclear blast". That's how New Jersey's governor described the 1994 explosion on a natural gas pipeline in his state.
For an extremely insightful look at a natural gas transportation pipeline accident that occurred near Maple Creek, Saskatchewan, read the Transportation Safety Board of Canada's (Dead Link) official report. This one's a classic - spontaneous rupture with ignition, defective shut-off valve, delays in emergency response: it burned for about seven hours, devastating 21 acres of pasture.
Closer to home, the June 10th, 1998 Gaz Metropolitain distribution system explosion in Old Montreal killed three and injured seventeen more, four of them critically.
As a matter of fact, in the Montreal area alone during the past thirty-three years there have been fifty-six fatalities, more than seventy-five serious injuries, and hundreds of people left homeless by natural gas accidents.
So, with all this potential for devestating accidents, at least there are effective emergency response plans in place to deal with them, right? Don't be too sure...