The Mississauga Miracle

It Ran Off the Track

At approximately 23:53 on Saturday 10 November 1979, as Train 54 crosses Burnhamthorpe Road, the journal bearing on Car 33 finally gives way. The temperature has long since exceeded 500°C. The bearing welds to the axle. The axle fractures. The wheelset separates.

The detached wheels and axle crash through a residential fence and land in the Riddels' backyard near Burnhamthorpe. But the crippled car does not stop. It continues on its remaining six wheels — four on the rails, two off — dragging its rear truck sides along the ties, shedding journal box steel, brake shoes, bearings, and lubricator pads at every crossing. It rides like this for over a mile. At Erindale Station Road, the front wheels of the trailing truck derail. Still the car keeps moving. Finally, at approximately 23:56, the whole rear truck catches on a switch near the Alkaril Chemical building just west of Mavis Road. The car derails. The twenty-three cars behind it pile up in a chain reaction of buckling steel and ruptured tankers.

Twenty-four cars leave the track. Twenty-one are tank cars. Nineteen are carrying dangerous goods.

"I was surprised we weren't killed. When it blew up and I saw that flash, I thought, 'Well, this is it.' But then everybody got up and nobody was hurt." — Chief Fire Inspector Cyril Hare, whose own home caught fire from the derailment

A Poison Cloud, a Flaming Sky

The propane fires are spectacular and terrifying. But it is the chlorine that keeps emergency officials awake for six days.

In the first hours, confusion reigns over what the train is actually carrying. Ed Nichol's manifest, recovered from the caboose, is difficult to read in the dark and smoke. An early rumour circulates that the train carries toxic PCBs — it does not. An updated manifest relayed from the CP dispatch office in Toronto eventually confirms the true cargo. The confirmation of chlorine is worse than PCBs.

Chlorine is a pale green-yellow gas, 2.5 times heavier than air. It sinks. It pools in basements, in ditches, in low-lying ground. At 30 parts per million it causes chest pain and coughing. At 400 ppm, it is lethal within thirty minutes. At 1,000 ppm, it kills within minutes. In the First World War, chlorine and its derivative phosgene were the primary killing agents of gas warfare — responsible for approximately 85,000 deaths.

The tanker on Train 54 carries 90 tonnes of it.

The lucky break

The derailment punctures the chlorine tanker, tearing a hole two and a half feet in diameter — large enough for a person to climb through. The safety relief valve fails to activate, and as the external fires heat the tank, a corrosive reaction between the liquid chlorine and the overheating steel shell accelerates the breach.

How much chlorine escapes is impossible to determine precisely — even the Grange Inquiry cannot establish an exact figure. What Justice Grange does establish is this: the BLEVEs of the propane cars "sucked up much of the Chlorine out of the tank and lifted it into the sky where it was dissipated more or less harmlessly." When Stu Greenwood of the Dow Chemical CHLOREP team manages to measure the remaining level on Monday — peering into a tank 102 inches deep — he finds two to three feet of liquid and ice remaining. He estimates roughly 20 tonnes are still inside. The rest — the majority of the 90-tonne payload — is gone. Under normal circumstances, this release would be catastrophic: a dense, lethal cloud rolling through suburban streets at ground level.

But the propane fires save Mississauga.

The massive fireballs draw the escaping chlorine gas upward. The heat column from the burning propane acts as a chimney, pulling the chlorine high into the atmosphere where it disperses over Lake Ontario rather than settling into streets and basements. The very thing that made the disaster look apocalyptic — the towering fireballs visible from Niagara Falls — is also the thing that prevents a mass poisoning. A subsequent review by The Economist estimated that the amount of chlorine present was sufficient to kill 24,000 people given the population density of the surrounding area.

Fire Chief Gordon Bentley and Etobicoke Fire Chief Bryan Mitchell recognise this dynamic — and make a counter-intuitive decision that may be the most important tactical call of the entire crisis. Rather than attempting to extinguish the propane fires, they implement a controlled burn strategy. Firefighters retreat to a safe distance and deploy ten master streams through over 4,000 metres of hose — not to put the fires out, but to cool the surrounding unexploded tank cars and let the propane burn off safely. Extinguishing the fires would collapse the thermal updraft. The chlorine would pool at ground level. The fires must keep burning.

The controlled burn takes 50 hours. The fires are finally declared out at dawn on Tuesday, 13 November.

Sealing the tanker

Greenwood's initial estimate of 20 tonnes is later revised downward. The ice layer — chlorine hydrate, formed when firefighting water entered the tank — is 6 to 12 inches thick, masking the true liquid level. Command post documents settle on "about 10 tons of liquid Chlorine." It continues leaking at roughly 35 pounds per hour by vapourisation. The leak cannot be sealed while propane fires still burn nearby.

Dow Chemical's CHLOREP team, which departed Sarnia at 03:30 and arrived at the scene by 06:30, cannot even locate the chlorine car on the first day because of the intensity of the fire. Procor, a railcar manufacturer, fabricates a steel patch. On Tuesday, after the fires die down, the patch is applied. By Wednesday, Greenwood tells the command post they have a "controlled situation" — but he cannot guarantee that something might not happen to the ice layer which might cause a sudden release of gas.

On Thursday, vacuuming begins. The Grange Inquiry records that an estimated 7.5 tonnes of chlorine are extracted between Thursday and the following Monday, much of it neutralised with caustic soda during the vacuuming process itself. The figures of weight transferred to trucks are unreliable because the neutralisation converts the chlorine before it can be weighed.

By Friday 16 November, the evacuation order for the inner zone is finally lifted. Mississauga can breathe again.

While the Immigrants Slept

This is a pre-mobile-phone world. It is the middle of the night. Most of Mississauga is asleep. And in the hours after the derailment, the authorities must wake a quarter of a million people and move them — calmly, safely, and fast.

"Our house shook. The windows rattled. The sky was bright orange, and when I saw the fireball, we were already running to the car, only with the clothes we had on, and on our way out of the city. We didn't even know where we were going." — Mississauga resident

Approximately 500 police officers are on duty at any given time. They drive through residential streets with loudspeakers and bullhorns, then go door to door, marking driveways with an "X" to signify a home has been emptied. Local radio and TV stations — CFRB, CHUM, CBC, and a dozen others — go to round-the-clock coverage, becoming the primary emergency broadcast system. Police process over 50,000 telephone enquiries from the public during the crisis.

The decision

At 07:30 on Sunday 11 November, a decision-making committee forms: Police Chief Doug Burrows, Fire Chief Gordon Bentley, Regional Chair of Peel Frank Bean, and Mayor Hazel McCallion. They are later joined by Ontario Solicitor General Roy McMurtry and Deputy Minister John Hilton.

Hurricane Hazel takes command

McCallion makes a strategic decision that will define the crisis. She defers all tactical operations — firefighting, perimeter control, hazmat response — to the police and fire chiefs. Instead, she assumes total control of public communication, inter-governmental liaison, and civic administration. She formally invokes emergency powers and makes an unprecedented declaration: Mississauga is "closed until further notice."

Early in the crisis, she severely sprains her ankle at an evacuation centre, but refuses medical leave. OPP Deputy Commissioner Jim Erskine physically carries her into press conferences. She holds continuous, transparent briefings — projecting stability and absolute authority at a moment when a quarter-million people need to know someone is in charge. Solicitor General McMurtry, recognising her effectiveness, largely defers to the mayor, avoiding the jurisdictional infighting that cripples so many disaster responses.

"If this had happened a half mile farther down the track, either east or west, we would have seen thousands of people wiped out. It's a miracle it happened here." — Mayor Hazel McCallion

The committee makes thirteen boundary adjustments over the next two days as wind direction — tracked continuously by Environment Canada meteorologists — chlorine readings, and fire conditions change. The evacuation zone expands steadily — first south to Lake Ontario, then east and west. By Sunday evening it includes parts of neighbouring Oakville. At its peak, the zone covers approximately 96 square kilometres.

The logistics

Three hospitals are cleared: Mississauga General, Oakville-Trafalgar Memorial, and Queensway. Six nursing homes are emptied. Over 2,000 patients are moved using 159 ambulances drawn from 25 regional services. The hospital clearances take eight hours.

Nineteen facilities serve as reception centres. Mayor McCallion opens Square One Shopping Centre — just 2.5 kilometres from the derailment site — as the primary shelter. Many evacuees arrive in nightclothes. The Canadian Red Cross, St. John's Ambulance, the Salvation Army, and the Mississauga and Ontario Humane Societies all deploy. Tens of thousands of people pass through the centres over the six-day crisis — though most evacuees stay with friends and family rather than in shelters. The Red Cross alone serves over 36,000 meals to evacuees and a similar number to emergency personnel. Local businesses provide free food and supplies.

The logistics of moving a quarter-million people work partly because of timing and demographics. Mississauga in 1979 is an affluent, heavily motorised suburban sprawl — nearly every household has at least one car. The disaster falls late on a Saturday night heading into the Remembrance Day long weekend: commuter traffic is non-existent, families are together at home, commercial activity is paused. Post-event studies reveal that over 85 per cent of households self-evacuate in their own vehicles. Approximately 85 per cent of evacuees go to the homes of friends and family in Toronto, Hamilton, and surrounding regions. The phased nature of the evacuation acts as a natural metering system, preventing gridlock on the QEW and Highway 401.

There is no panic. People pack what they can and go. Families are separated with no easy way to find each other — this is 1979, and mobile phones are decades away.

"I went to bed in Mississauga and woke up in Oakville." — Matthew Wilkinson, Heritage Mississauga historian, evacuated as a child

Firefighters enter evacuated homes to feed pets after residents drop house keys at City Hall. No animals die. Children later remember the evacuation as a "fun adventure" — waking up somewhere unfamiliar, sleeping on gymnasium floors, the excitement of disrupted routine. The adults remember the fear.

The return

On 13 November, after the propane fires are finally extinguished following roughly 50 hours of burning, air sampling confirms safety in the outer zones. 144,000 residents are allowed home. On 16 November, after the chlorine is pumped out, 37,000 more return. At 19:45 that evening — nearly six full days after the derailment — the last roadblocks come down. The city reopens.

There's No Hero, There's No Villain

The Mississauga Miracle earned its name. But the margins between miracle and catastrophe were razor-thin. Change any one of several variables and the story ends very differently.

"If he hadn't done that, more than half of Mississauga would have gone up." — Engineer Keith Pruss, on Larry Krupa's decision to uncouple the cars