One geothermal station is almost as bad as burning gas. Made with funding from NZ On Air.
WorkSafe has laid charges against Mercury Energy after a power plant malfunction led to the release of scalding geothermal steam the regulator alleges could have killed or seriously injured workers.
A leading health and safety lawyer says it is the first time he can recall that a power company hasbeen charged in this way by the workplace safety regulator.
No one was injured in the incident during the commissioning of new equipment at the Rotokawa geothermal power station northeast of Taupo on July 7, 2021.
It is understood a cascading series of potentially avoidable technology issues allegedly led to a dangerous phenomenon called "steam hammer" in some of the plant's pipes.
Steam hammer happens when steam comes into contact with condensation and rapidly changes in pressure, resulting in a violent hammering and rattling in pipes that can lead to a catastrophic failure.
At the plant on July 7, it led to what WorkSafe described as an uncontrolled release of geothermal fluids at high temperatures and pressures, resulting in discharge of plumes of steam in areas where staff could have been working.
Mercury generation general manager Stew Hamilton said in a statement the uncontrolled discharge happened during commissioning of "rebalancing" works at the plant aimed to increase its power generation capacity.
"Although there were no injuries, Mercury notified WorkSafe and has been working with them to investigate and provide insight into the causes of the incident."
About a year after the incident WorkSafe told the power company they were laying charges under the Health and Safety at Work Act due to the risk workers could have been harmed.
"We are in the process of reviewing the charges and seeking further information to decide on how best to respond," Hamilton said.
"We take the health and safety of people at our sites very seriously and have been progressing with significant work to address this risk over the last 12 months and will continue to work closely with WorkSafe to improve the process safety risks at all of our sites."
WorkSafe has laid charges against Mercury Energy after a power plant malfunction led to the release of scalding geothermal steam. Photo / Christine Cornege
The company is scheduled to appear in the Taupō District Court on August 31.
It faces two charges.
The first charge, under Section 36 of the Act, alleges the company did not ensure the safety of workers so far as is reasonably practical
The second is under the less frequently used Section 43, requiring companies to protect the safety of workers during the construction or commissioning of a plant or structure.
Grant Nicholson, a partner at Anthony Harper and among New Zealand's leading health and safety lawyers, said it was the first time he could recall that a power company has been charged under the Health and Safety at Work Act 2015.
He said health and safety legislation does not just apply to the direct employees of a company, but also to contractors.
"With Section 43 in particular, you've got to think of the health and safety of the people who are doing the installation or production, you've got to think of the people who are going to use it, and the people who are going to do any sort of reasonably foreseeable work on it."
Nicholson said in recent years WorkSafe had become more willing to bring prosecutions for alleged health and safety breaches.
"It's not like they're going out and charging hundreds and hundreds of people more than they were before.
"But what we are seeing is that when they're taking charges, they're being a little more creative in the way they go about it.
"Take this as an example. We've noticed a little bit of a trend with WorkSafe now being willing to take charges in circumstances where people haven't actually been hurt, but where they've been exposed to the risk of harm.
"It's something that wasn't very frequently done, historically, but it's becoming more common now."
If convicted, Mercury faces maximum fines of $1.5 million for each of the two charges.
