Do you know anything about the explosion? Email us your photos and information
The mammoth pipeline project that yesterday cost a female worker her life was dogged by delays and being forced through uncharted terrain.
A 48-year-old woman died and six workmates were taken to hospital after an underground gas explosion in Onehunga, Auckland.
As emergency services cordoned off the scene, details were emerging of the race to complete the project on time - and the factors complicating the work.
The terrain where the explosion occurred is notoriously difficult. The land is predominantly hardened lava field with huge pockets of largely uncharted tunnels and caves.
Officials had sought information from Watercare about the terrain, particularly on the likelihood of lava caves in the area.
A report prepared by Watercare in March last year for the former Auckland Regional Council conceded radar probes had failed to reveal exactly what was underground.
"A trial ground penetrating radar investigation was undertaken for known underground services in Mt Smart Rd and ... in the Te Kawa Rd/Campbell Rd area.
"For each of the trials the method was unsuccessful in detecting known features and therefore was not deemed to be a sufficiently useful technique for the detection of unknown features along other sections of the route."
Australian designers GHD, who worked on the project in 2008, also made specific reference to the terrain.
The company pointed out the ground conditions varied widely from soft peats to hard basalts.
This weekend's work, under Victoria St and Mt Smart Rd, had an added complication - a cross-connection or joining of two pipes.
It required extensive traffic management, including road closures at various stages.
Maungakiekie-Tamaki Local Board deputy chairwoman Bridget Graham said the board was briefed by Watercare a fortnight ago.
Watercare had told the board the area was very difficult to work in, she said.
"This was a very tricky part, [Watercare] were clear about that. One tunnel has to go under another and two watermains meet and have to be joined. They said at the time this was going to cause a few difficulties."
A worker for Watercare contractor HEB Construction, who declined to be named, said contractors also had to contend with a massive amount of utilities in the ground at the location of the explosion.
"It's horrific underground. There's old powerlines, old gas pipes still there, new gas pipes, there's telecommunication cables, old cables, low- and high-pressure mains."
Sources close to the project said contractors were under pressure to complete the work with round-the-clock shifts over the holiday weekend.
A public notice posted by Auckland Transport said road closures would be needed only up until Thursday, June 2.
HEB chief executive Derrick Adams confirmed Queen's Birthday Weekend was a critical period.
"This involved a major shutdown of a major water supply into Auckland. It was to take advantage of the lower water use over the holiday. This was an activity that was planned some months ago."
In a statement, Watercare confirmed its staff were onsite with contractors at the time of the explosion.
Watercare chief executive Mark Ford would not speculate on any of the factors which led to the calamity.
"We are not in a position to say at this stage what caused the explosion. However, we are working closely with the contractors and all the authorities, including the police, Fire Service and the Department of Labour."
HEB has nationwide civil construction contracts.
The company was founded by Bruce Pulman more than 28 years ago and it remains owned by the Pulman Family.
Pulman also founded and remains a director of the Bruce Pulman Park Trust, a charity providing sports and recreation facilities in Papakura.
The firm is also building the $445 million Tauranga Eastern Link roading project in a joint project with Fulton Hogan.
Eventually the pipeline being laid under Onehunga will extend to the Khyber reservoirs in the city centre.
It is 1.3 to 1.9 metres in diameter and will be mostly laid under roads.
For most of the route, open trenching methods were being used to lay the watermain.
