Change to height and volume of dams impacted by the dam safety regulations

The new regulations on dam safety come into force on 13 May 2024.

The regulations have been made to increase the resilience and safety of Aotearoa/New Zealand’s dams, protecting people, property and the environment from the potential impacts of dam failures. They also provide a nationally consistent risk-based approach to dam safety.

Only dams that meet a certain height and volume threshold are impacted by the regulations and need to be classified.

A change to the thresholds

The Government has recently made a change to the thresholds to reduce the number of dams that need to be classified. This follows concerns from the sector that a higher number of small, low impact dams were captured by the regulations than what was originally intended. There were also concerns that associated costs were not proportionate to the potential risks these dams pose.

It is important that specialist engineering resources are focussed on dams that represent the greatest risk to people and property downstream, and that owners of classifiable dams can efficiently meet their obligations under the regulations.

In response to the concerns, the Ministry of Business, Innovation and Employment (MBIE) carried out targeted consultation in January 2024, exploring options to potentially change the height and volume thresholds for classifiable dams.

As a result of the feedback received from the consultation, the Government has removed the lower of the 2 thresholds, meaning that fewer smaller dams will now be impacted by the regulations.

The new threshold at which dams need to be classified

Now, dams only need to classified if they are 4 or more metres in height and store 20,000 or more cubic metres volume of water, or other fluid.

Dams that are 1 or more metres in height and store 40,000 or more cubic metres volume of water, or other fluid, no longer need to be classified and are not impacted by the regulations.

The implementation timeframes for when dam owners need to submit documentation to the relevant regional authority, and when they must carry out reviews, are not changing.

Actions for dam owners to take

Dam owners will need to check if their dam/s meets the new threshold. If it still does, they will need to carry out a potential impact classification (PIC) to assess the potential impact (ie low, medium or high) their dam’s failure could have on the community, historical or cultural places, critical or major infrastructure, and the natural environment.

The regulations allow for anyone to carry out a PIC assessment (eg dam owners, farm consultants, technical practitioners). The role of a Recognised Engineer is to audit and certify these PIC assessments.

The regulations come into force on 13 May 2024, and dam owners must provide their dam’s classification certificate (which they will need to get certified by a Recognised Engineer) to their regional authority by 13 August 2024.

Other actions dam owners need to take depend on whether their dam is assessed as low, medium or high impact. Owners of dams assessed as having a low potential impact will have fewer responsibilities, whereas those with a medium or high potential impact will have more responsibilities.

Information and resources to support dam owners

Information and resources are available on MBIE’s Building Performance website. Resources include a detailed guidance document and a resource to help dam owners calculate the height and volume of their dam, to see if it is impacted by the regulations.

Managing dams to ensure they are safe(external link) – Building Performance

Implementation timeframes(external link) – Building Performance

Resources(external link) – Building Performance

Engineering New Zealand Te Ao Rangahau has information on its website about how to find an engineer and/or a Recognised Engineer, and tips how to effectively engage with them.

Tips on engaging an engineer(external link) - Engineering New Zealand Te Ao Rangahau

How to find a Recognised Engineer(external link) - Engineering New Zealand Te Ao Rangahau