Cause of Blasts Baffles Officials

Jan. 21, 2004
JOHN HERBERT, Free Press Reporter

London Hydro said yesterday it doesn't know what caused explosions Monday night in downtown London that sent manhole covers flying and flames towering into the sky. A London Hydro official said it's possible a substance may have leaked into an electrical chamber beneath King Street and combined with standing water to create an "explosive mixture.''

Ed Jambor said an electrical cable fault or arc triggered the blast at 7 p.m. Monday on King Street near Galleria London.

"What was in that manhole that caused it to explode so violently, whether it was something other than what is normally in those manholes, we just don't know,'' Jambor said yesterday.

Methane gas and natural gas weren't detected, he said.

Jambor couldn't explain how sparks could trigger such a massive explosion in a network of underground cables.

"The downtown system has a lot of energy in it, but I've never heard of a fault with such magnitude causing an explosion before,'' he added.

"The simple explanation could be it was a really unusual cable fault. Once the smoke clears, we'll be talking to other utilities in other communities to find out if they have experienced similar failures."

Ron Standish, the city's director of waste water and treatment, said the explosions were not in the city's sewer system.

Ed Christie, a spokesperson with Stabiloc, a Detroit-area company that manufactures locking mechanisms for manhole covers, said explosions such as the one in London are common in American cities.

He said in most cases, methane gas is the cause. But in some cases runoff of flammable liquids causes explosions. It's also possible gasoline could have been be poured into the chamber, Christie said.

An explosion wouldn't occur until salt and water eats away at cables corroding them to the point arcing would occur, he said.

The cables in the chamber -- half of them about 10 centimetres thick -- have the capacity to carry 30 megawatts of power, enough to light up downtown.

At the time, about 15 megawatts were in the system.

The chamber on King Street and others downtown allow hydro crews to access to the underground network of cables in the city.

There is no transformer in the chamber in which the explosion occurred, Jambor said.

The blast Monday caused $100,000 in damage to electrical equipment.

The explosions about 7 p.m. sent hundreds of people into the streets as Galleria London and the Central Library along with restaurants in the area of King and Clarence streets were evacuated by London police.

Officers blocked off an area bounded by Richmond, Wellington, York and Dundas streets. There were no injuries, but two manhole covers were sent several metres into the air, while two others were dislodged by pressure from the underground explosions. One manhole lid nearly struck a police officer.

Power was shut off on overnight Monday into yesterday morning at some downtown businesses while hydro crews assessed damage. At the same time, police closed King Street between Clarence and Wellington streets. The street could reopen today.

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