The regulations come into effect on 13 May 2024. From this date, owners of dams that meet the classifiable dam height and volume thresholds are required to classify their dam according to the potential impact of a failure of the dam, and have the classification audited and certified by a recognised engineer.

The recognised engineer certifies if the classifiable dam has a low, medium or high potential impact classification. The potential impact assessment considers the impact to the community, cultural sites, critical and major infrastructure, and the natural environment.

If it is a medium or high potential impact dam, the Building Act then requires the owner to prepare a dam safety assurance programme e.g. dam safety plans and dam inspections etc.

A classifiable dam (as defined in regulation 5 of the Regulations) is a dam that is four (4) metres or more in height and holding 20,000m³ or more in volume*.

*This definition was changed by the New Zealand Government on 28 March 2024 and comes into effect on 13 May 2024.

This proposed policy applies to dams that have a high potential impact classification or a medium potential impact classification and that are likely to fail in the ordinary course of events (“dangerous dam”), or a “moderate earthquake” or “moderate flood” (as defined in the regulations).

These terms are defined in the Building Act. The Building Act states that a dam is dangerous if it is:

A high potential or medium potential impact dam; and is likely to fail –

• In the ordinary course of events; or
• In a moderate earthquake (as defined in the regulations); or
• In a moderate flood (as defined in the regulations).

A dam is an earthquake-prone dam for the purposes of the Building Act if the dam –

a. Is a high potential impact dam or a medium potential impact dam; and

b. Is likely to fail in an earthquake threshold event (as defined in the regulations).

A dam is a flood-prone dam for the purposes of the Building Act if the dam -

a. Is a high potential impact dam or a medium potential impact dam; and

b. Is likely to fail in a threshold event (as defined in the regulations).

The dam owner or recognised engineer must immediately notify Horizons if they believe a dam is dangerous, earth-quake prone or flood-prone.

The policy sets out what Horizons will do if we are notified of a dangerous dam, earthquake-prone or flood-prone dam in our region.

The policy has three key sections:

1. How we will perform our legislative functions in relation to dangerous, earthquake-prone or flood-prone dams.

We have a variety of functions under the Building Act, and our approach is explained in more detail in the policy.

2. Our priorities when performing these functions.

The policy sets out that we will prioritise safety at all times, following a risk-based approach. When undertaking our functions, we will also protect the health and wellbeing of the environment and have regard to cultural and heritage values.

3. How the policy will apply to heritage dams.

If a dangerous dam has been classed as a heritage dam, we will account for the need to facilitate the preservation of significant heritage values.

The policy does not apply to all dams or farm ponds. It only applies to classifiable dams that are either a high potential impact dam or a medium potential impact dam that are likely to fail in the ordinary course of events (“dangerous dam”), or a “moderate earthquake” or “moderate flood” as defined in the Building Act.

The policy does not classify dams. The regulations require the owner to classify their dam according to the potential impact of a failure of the dam, and have the classification audited and certified by a recognised engineer.

The policy also does not cover consenting matters under the Resource Management Act 1991.

Submissions should relate to the contents of the dams policy. Horizons Regional Council is not able to change anything in the Building Act or the Building (Dam Safety) regulations.