What are Dangerous, Earthquake-prone and Flood-prone dams?
The Building Act 2004 states that a dam is dangerous if it is a high potential or medium potential impact dam; and is likely to fail –
a. in the ordinary course of events;
b. or in a moderate earthquake (as defined in the Regulations);
c. or in a moderate flood (as defined in the Regulations).
A dam is an earthquake-prone dam for the purposes of the 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 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 flood threshold event (as defined in the Regulations).
Policy on Dangerous Dams, Earthquake-prone Dams and Flood-prone Dams
The Bay of Plenty region has a number of large dams that are used for a variety of purposes including hydroelectric generation, water supply, flood control, irrigation, farm stock supply and recreation.
The Building Act 2004 introduced legislation for managing the safety of existing and new dams in New Zealand. Under this Act, regional councils must have a policy on how they will deal with dangerous dams, earthquake-prone dams and flood-prone dams and how the policy will apply to heritage dams.
The link to the updated “Policy on Dangerous Dams, Earthquake-prone Dams and Flood Prone Dams 2024” is provided below in the list of relevant important documents.
What has changed under the new Regulations 2022?
The new regulations require owners of dangerous, earthquake-prone and /or flood-prone dams to determine if they own a classifiable dam.
Key aspects the new regulations address are:
- A dam is considered a ‘classifiable dam’ if it has a height of 4m or more and impounds 20,000m3 or more of water or fluids.
- If a dam is classifiable, the dam owner is required to assess the Potential Impact Classification (PIC) of the dam.
"The PIC is the potential impact of a dam on the community, historical or
cultural places, critical or major infrastructure, and the natural
environment in an event where the dam suffers failure. The PIC of a
dam will be assessed as either low, medium, or high."
Dam owners can determine their dam's PIC themselves, but will need to have the PIC audited and certified by a Recognised Engineer. The PIC is to be lodged with Bay of Plenty Regional Council by 27 December 2024.
Please see Schedule 2 of the regulations to understand how to determine your dam’s PIC.
If the PIC assesses the dam as having Medium or High Potential Impact, the dam owner is required to:
- Develop or update a Dam Safety Assurance Programme (DSAP).
- Have the DSAP audited and certified by a recognised engineer*.
- Lodge the certified DSAP with Bay of Plenty Regional Council.
- Each year submit an Annual Dam Compliance Certificate.
* Please see the qualification and competency requirements of a recognised engineer to certify PIC or DSAP before engaging someone for this purpose.
How was the Policy developed?
Section 161 of the Building Act 2004 requires the policy to state:
(1) The approach regional council will take in performing its functions under this Part; and
(2) Regional Council’s priorities in performing those functions; and
(3) How the policy will apply to heritage dams.
Regional Council followed the special consultative procedure set out in section 83 of the Local Government Act 2002 to update and adopt the policy. Following are key dates from the policy update process:
- 25 June 2024 - Draft Policy adopted for public consultation.
- 26 June 2024 - Consultation open
- 29 July 2024 - Consultation close
- 14 August 2024 - Deliberations
- 17 September 2024 - Final Policy adopted by Strategy and Policy Committee
- 27 September 2024 - The Policy on Dangerous Dams, Earthquake-prone Dams and Flood-prone Dams is made operative and commences for the Bay of Plenty Region.
