Residents, bach owners and farmers are being told to vacate properties and move stock behind an exclusion zone as urgent repairs are done to the Maui gas pipeline in Taranaki over the weekend.
Photo: 123RF
Firstgas says the no-go zones will protect people and livestock from the noise of high-pressure gas being vented from the pipe, but some locals fear there is a more sinister risk.
As residents pack up their lives for a weekend away from home, some are feeling nervous.
They are vacating so Firstgas can reconnect two repaired and realigned sections of the Maui pipeline - one at Pariroa near Tongaporutu and the other at Gilbert Stream off Pukearuhe Road in Mimi.
The work requires about 400,000 cubic metres of gas to be vented at three locations, including one alongside State Highway 3.
It is being is timed to coincide with Auckland Anniversary weekend to minimise disruption to supply.
In a statement, Firstgas said it had liaised with the community and worked with the Taranaki Regional Council and Worksafe to ensure its safety controls were robust.
But a bach owner - who preferred not to be identified - did not think locals were getting the full picture.
"Explosion risk is the elephant in the room, but this is when we talk about a low probability higher consequence event when the chances of it happening is very low but if it does happen it is catastrophic."
He said there had been no warning of a potential explosion risk.
"For some reason, and I don't know what the reason is, they are just avoiding this whole issue completely and they are focusing on something which is of nuisance value.
"Yes, it's a loud noise and it can potentially affect livestock etc, but it's at the nuisance level compared with something that actually does threaten lives."
Retired energy analyst Steve Goldthorpe looked at Firstgas' plans for the lobby group Energy Watch Taranaki.
He said it was not unusual to vent pipes to do maintenance, but the scale of what was proposed concerned him.
"What's different about this one is the length of pipeline which is some 20 kilometres or more full of high-pressure gas that's all proposed to be released into the atmosphere."
Goldthorpe, who was convener of the Sustainable Energy Forum, said the greatest risk would occur when the discharge was nearly over and pressure was lost - meaning gas could pool near ignition sources.
"If the worst came to the worst and it caught fire and exploded it would be a very large energy release.
"From my calculations the size of energy release would be about the same as the explosion in Beirut back in 2020."
In a statement, WorkSafe said it had reviewed Firstgas' plans and concluded the overall risk appeared to be low.
But in an email to Goldthorpe it acknowledged risk of explosion formed part of the company's planning.
"Firstgas has completed detailed dispersion modelling to review all the possible scenarios and the consequences for different weather conditions and considered the worst-case scenario in terms of dispersion and explosion to assess the required safeguards.
"Exclusion zones of 1 kilometre from the release points have been identified and will be observed."
WorkSafe said the risk of ignition from passing vehicles at the Mōkau compression unit was considered low, explaining why SH3 was remaining open.
Firstgas said locals had not been told of an explosion risk because there was none.
"The safety of all involved has been our top priority and independent modelling for this work shows this isn't a possible scenario.
"Firstgas has assessed the safety of the natural gas release and determined the appropriate minimum wind speeds and atmospheric conditions to ensure the gas release is safely dispersed."
The venting was scheduled to occur for two hours from midnight tonight.
The realignment work would then be completed over the following 50 to 60 hours.