Strength of blast blew staff into second pipe

The cause of an explosion in the Auckland suburb of Onehunga which claimed the life of a 48-year-old woman on Saturday remains unknown. Photo / Dean Purcell

The woman killed in the weekend's watermain explosion and a seriously injured colleague are believed to have been blown out of one section of pipe and into another by the force of the blast.

Two sources said yesterday that Philomen Gulland and Ian Winson were several metres inside one section of an existing watermain inspecting its condition when the gas explosion occurred shortly after 8am on Saturday.

The force is understood to have propelled the two Watercare workers out of the pipe, past a trench and into another section of the pipe, from where they were recovered by emergency services.

Shortly before the explosion in Onehunga, a 3m section of the watermain had been removed to connect to a new watermain.

Ms Gulland, a 48-year-old Canadian-born mother of two and maintenance planner, was killed and Mr Winson, a network engineer, lost part of both legs.

The pair were wearing gas detectors that measured oxygen, carbon monoxide, carbon dioxide and low explosive levels.

The detectors are designed to flash and beep if any of these measures are outside the control settings.

The pair were also wearing harnesses that were connected by rope to two Watercare colleagues in the trench outside the 2m-wide watermain.

It is understood that as well as the two Watercare workers inside the watermain and their two colleagues holding the harness ropes, three workers from HEB Construction were in the trench near the main at the time of the explosion.

About 20 workers were in the trench when the 3m section of pipe was cut about 7.15am.

HEB Construction chief executive Derrick Adams said he hoped work would start today on completing the connection of a new pipe and resume water supplies on one of the city's major watermains. The work is expected to take about 12 hours.

Work had been due to begin yesterday, but was halted about midnight on Sunday after gas was smelled about 500m away in Mays Rd.

The Fire Service was called and utility company Vector began testing. Last night, a Vector spokeswoman said no leaks were found.

Watercare resumed work on the site about 11.30am yesterday, blasting air through the pipes, cleaning them and monitoring them with gas detectors and a mobile closed circuit television camera.

At a press conference yesterday, Watercare chief executive Mark Ford continued his line of refusing to comment on the explosion, saying it was a matter for the emergency services and Department of Labour to determine.

On Sunday, Fire Service area commander Murray Binning said that methane gas had been found in the pipeline but he did not know the source of the gas or what caused the explosion.

Yesterday, Mr Ford said if any gas was detected, no staff would go near the site, where work had been taking place for two months without any sign of gas - before Saturday. "We are not going to take the risk. We are going to rely on expertise.

"We will be talking to Vector. Obviously the Department of Labour won't let us go back if they believe there is any danger," he said.

Mr Adams said the purpose of the monitoring regime was to assure workers there was no gas in the pipeline or the immediate area.

"We will have a period of that being completely clear before we go anywhere near it with our workers."