We have accepted an enforceable undertaking from Mercury NZ Limited (Mercury).


On 7 July 2021, during commissioning activities at Rotokawa Power Station, fluids with significantly different temperatures unintentionally mixed, resulting in a severe steam hammer event that damaged valves and pipework, leading to the loss of steam containment. No injuries were sustained.

Alleged contravention

Being a PCBU having a duty to ensure, so far as is reasonably practicable, the health and safety of workers who work for the PCBU, including while the workers are at work in the business or undertaking, namely commissioning work at Rotokawa Geothermal Ormat Binary Power Station, did fail to comply with that duty, and that failure exposed the workers to risk of death, or serious injury.

Being a PCBU having a duty, so far as is reasonably practicable, to ensure that the way items of plant were installed at the Rotokawa Geothermal Ormat Binary Power Station (RGN) facility was without risks to the health and safety of persons at or in the vicinity of the workplace, whose health could be affected by use of those items, did fail to comply with that duty, and that failure exposed those persons to a risk of death or serious injury.

Summary highlights of the enforceable undertaking

  • Delivery of a programme to empower leaders in promoting a proactive safety culture.
  • Undertake a trial with a self-driving vehicle for plant inspections.
  • Develop and implement a training programme focused on hazard awareness and safety in high-risk environments.
  • Sharing incident learnings and resources developed as part of the enforceable undertaking with a wide audience.

Reasons for accepting the undertaking

The enforceable undertaking meets the requirements of WorkSafe’s Enforceable Undertakings Operational Policy (September 2019), considering:

  • The activities in the enforceable undertaking and how they promote progressively higher standards of work health and safety.
  • The nature of the alleged contravention and how serious it was.
  • Information received from any interested party in relation to the contravention.
  • Mitigation and remedial action, already taken or planned, regarding both the contravention and any person affected by the contravention (including victims).
  • The business’s past performance and compliance history with health and safety legislation.
  • Any likely outcome if the matter were dealt with by legal proceedings.
    • A charge was filed in relation to this incident on the basis that there was both evidential sufficiency and public interest in initiating prosecution.
    • The undertaking accounts for the benefits that accrue to Mercury by a prosecution not proceeding.
  • Any other matter which WorkSafe thinks is relevant.
    • The undertaking delivers benefits beyond compliance.
    • The undertaking supports WorkSafe’s strategic objectives.
    • The undertaking contains acceptable terms.

Date accepted

1 March 2024

Further information

View the Mercury NZ Limited enforceable undertaking

Enforceable undertaking – Mercury NZ Limited (PDF 1.8 MB)