Onehunga explosion: Company denies workers needed to test for gas

The site of the recent trench explosion. Photo / NZ Herald

A contracting company has denied its workers had a responsibility to test for flammable gases before using a blow torch that sparked a fatal explosion.

Canadian Pacific Limited (CPL) is defending two charges laid by the Ministry of Business, Innovation and Employment (MBIE) in relation to an explosion in an Onehunga watermain on June 4, 2011.

Closing submissions in the case, which began on September 2, were heard in the Auckland District Court before Judge Rob Ronayne today.

The explosion in the drained waterpipe killed Watercare employee Philomen Gulland, 48, and injured several others, including engineer Ian Winson, who later had both legs amputated above the knee.

CPL workers were replacing an air valve on the water pipe under contract to Watercare Services Limited, at the same time as a four-person inspection team, including Mr Winson and Ms Gulland, were entering the main at another location.

It's accepted that a gas torch used by a CPL worker to remove the air valve probably provided the ignition for explosive gases that had been drawn into the waterpipe as it was being drained.

The company was charged with failing to take all practicable steps to ensure its employees were not harmed, and failing to take all practicable steps to ensure its employees' actions or inactions did not cause harm to others.

MBIE prosecutor Shona Carr said the company failed to identify the potential hazard of explosive gas being present in the air valve chamber, failed to follow Watercare procedures which included applying for a hot work permit, and failed to test and monitor for explosive gases.

Mrs Carr said the information the company had or ought to have before the work was carried out should have prompted them to take such precautionary steps.

It was accepted that the steps may not have prevented the explosion, Mrs Carr said, but they should have been carried out anyway.

Lawyer for CPL, Paul White, said there was nothing about the circumstances of that particular air valve chamber that indicated a risk of explosive gas being present.

He said CPL's position was that there was no requirement to monitor for gas in the chamber, and in any case monitoring would have been ineffective in identifying a leak.

"Canadian Pacific's position is that there was no way they could foresee the actual hazard that was present inside the water pipe with what it knew on that day.''

Judge Ronayne reserved his decision.

Last week Watercare Services Ltd pleaded guilty to two charges in relation to the explosion, while a third was withdrawn by MBIE.

One of the charges related to failing to take all practicable steps to ensure the safety of its employees, and the other to failing to take all practicable steps to ensure the safety of its contractor's employees.

Watercare will be sentenced on Friday.