Underground transformer explodes in Toronto hydro vault beneath King Street

What happened

On Monday 1 May 2017, at about 5:15 p.m., a transformer exploded and burned in an underground Toronto Hydro vault beneath the Royal Bank building at 20 King Street West in Toronto, Ontario. The blast filled the street and the surrounding business district with thick smoke during a downpour. Nobody was hurt. Toronto Fire Services did not declare the vault safe to access until the following day. Its platoon chief reported three levels of soot down to the sub-basement and significant damage in the transformer room.

Crews later removed the charred transformer from the vault. Toronto Hydro said the cause was not yet known and would not be established until all equipment had been examined in a full investigation. The vault had last been inspected that autumn and was found to be in good working order. Toronto Hydro operates about 11,000 vaults, most of them downtown, and inspects each one every three years.

Contributing factors

Not yet determined. The downpour during the incident was noted, but the source says it was not clear whether weather was a factor.

Lessons learned

1. Underground vault fires can spread smoke and soot well beyond the vault, so operators in dense urban areas should plan for ventilation, soot damage and clean-up across several levels of a building.
2. Emergency services may be unable to access an underground vault until the structure is declared safe, so response plans should allow for delayed access.
3. Failed equipment should be secured and retained for a full investigation before clean-up begins, so that the root cause can be established.

More lessons on spacing, layout and fire spread, emergency response and public communication, investigation and fleet-wide checks, from every incident on the register.

Source

cbc.ca