The actions of a contractor working with a blow torch probably caused the fatal gas explosion in a waterpipe in Onehunga in 2011, a court has heard.
Contractor Canadian Pacific Limited (CPL) is defending two charges under the Health and Safety in Employment Act in relation to the blast.
Watercare employee Philomen Gulland, 48, was killed in the explosion while inspecting the watermain on June 4, 2011. Engineer Ian Winson later had both of his legs amputated above the knee. Several other people were injured in the explosion.
A defended hearing began before Judge Rob Ronayne began at Auckland District court this morning.
Ministry of Business, Innovation and Employment prosecutor Shona Carr told the court CPL employees who were carrying out work on an air valve using a gas torch probably provided the ignition for the fatal explosion.
It ignited natural gas from the Vector gas distribution network which had been drawn into a watermain through its air valves while it was being drained.
MBIE alleges CPL failed to identify the hazard of explosive gas being present when its employees were working on an air valve on the watermain, failed to monitor the atmosphere in the work space for explosive gas.
Mrs Carr said it wasn't known whether the monitoring would have detected the gas and prevented the explosion, but it was a practicable step that CPL should have carried out anyway.
At the time of the explosion, Watercare Services was installing a new water main, Hunua 4, along the same path as an existing main, Hunua 3.
In order to install a connecting T-section, Hunua 3 had been drained of water.
Mrs Carr said a four-person inspection team, which included Ms Gulland and Mr Winson, was being sent into Hunua 3 while, at the same time, pipe specialists CPL had been contracted to fix an air valve on the pipe, about 500m east on Mays Rd.
When Ms Gulland and Mr Winson entered the pipe their personal gas alarms sounded, so a fan was brought in to ventilate the pipe and they entered again a short time later.
"After Ms Gulland and Mr Winson had taken a few steps into the pipe an explosion occurred,'' Mrs Carr said.
Mrs Carr said CPL workers had gas monitors on them, but did not use them to monitor the atmosphere in the air valve chamber.
The company had also failed to follow Watercare's procedures relating to working in restricted spaces, which would have required gas monitoring.
CPL faces two charges under the Act, failing to take all practicable steps to ensure it's employees were not harmed, and that it failed to take all practicable steps to ensure it's employees' actions did not cause harm to others.
Watercare Services Ltd earlier today pleaded guilty to two charges, while a third was withdrawn by MBIE.
One of the charges relates 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.
The charge withdrawn related to failing to ensure the safety of CPL employees.
Watercare will be sentenced next week.
In a statement afterwards, Watercare said it had taken responsibility for health and safety breaches before the fatal explosion.
"Watercare has pleaded guilty to these charges. Since that terrible day we have made every effort to understand what actually happened to ensure something like this cannot happen again. That is the minimum we owe those involved,'' Watercare chief executive Mark Ford said.
"We continue to extend our support and ongoing sympathy to those involved and their families,'' he said.
The incident had deeply affected the company and it had reviewed its processes and reinforced its health and safety training since.
Speaking from their home in Green Bay, Auckland today, Mr Winson's wife Katherine said today: "We've got no comment to make at all.''