Building consent for large dams

A "dam" is an artificial barrier, and its appurtenant structures, constructed to hold back water or other fluid under constant pressure so as to form a reservoir; and is used for the storage, control, or diversion of water or other fluids.  This definition also includes flood control dams, natural features that have been significantly modified to function as a dam, and canals.  A "dam" does not include a stopbank designed to control floodwaters.

"Large dam" means a dam that has a height of four or more meters and holds 20,000 or more cubic meters volume of water or other fluid.

Do I need a resource consent or building consent to build a dam?

Resource consents

Resource consents are often required for dams as they involve the taking, using, damming and diverting of water and controlling of the quantity, level and flow of water. Also, the works associated with the dam construction itself can often trigger the requirement for resource consent.

Building consents

A building consent is required for all structures that meet the definition of a ‘large dam’ (see above definition), as well as those structures that form part of the large dam structure itself — such as appurtenant structures.

The construction of any dam, that is not a large dam is ’exempt” building work, and does not require a building consent, nevertheless section 17 of the Building Act requires all building work on dams to comply with the Building Code irrespective of the size of the dam.

This applies to the construction of new dams, the modifications of existing dams and also applies to appurtenant structures of dams.

Once details of your project are known you should discuss your development with council to identify if any resource or building consent will be required.

Dam Safety

Overview of Dam Safety Regulations 2022 

The Building (Dam Safety) Regulations 2022 were announced by the Ministry of Business, Innovation and Employment (MBIE) in May 2022. 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.

These regulations come into force on 13 May 2024.

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

Read more about managing dams to ensure they are safe on the Building Performance website 

Changes to the regulations 

On 28 March 2024, the Government changed the height and volume thresholds of a classifiable dam. The regulations will no longer apply to dams that are less than four meters high, regardless of their storage volume.

These changes now mean that classifiable dam now has the same meaning as large dam.

Government will change the Building (Dam Safety) Regulations 2022, Section 5(1) in due course to show the amended meaning of a classifiable dam.

Read more about the changes on the MBIE website

Dam Classification Certificate 

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

The PIC can be either low, medium or high.

Dam owners must provide their dam’s classification certificate (which they will need to get certified by a Recognised Engineer) to Council by 13 August 2024.

Forms are available from Waikato Regional Council’s Dam Forms - Dam Safety Scheme page.

Contact building@ncc.govt.nz to submit your Dam Classification Certificate.

Dam owners may have further obligations depending 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.

Dam Safety Assurance Programme 

A Dam Safety Assurance Programme (DSAP) is only required for dams with a medium or high PIC.

The DSAP provides dam owners with a structured framework of plans and procedures to plan and complete the activities required for the safe operation and management of their dams.

For a medium PIC dam, the DSAP must be:

• Certified by a recognised engineer and submitted to Council for approval up to two years after the regional authority approves the PIC. 
• It must be reviewed within 10 years after the date which the regional authority approves the DSAP, and then after the first review, at intervals of not more than seven years. 

For a high PIC dam, the DSAP must be:

• Certified by a recognised engineer and submitted to Council for approval up to one year after the regional authority approves the PIC. 
• It must be reviewed within five years after the date which the regional authority approves the DSAP, and then after the first review, at intervals of not more than five years. 

Annual Dam Compliance Certificate 

An annual dam compliance certificate is only required for dams with a medium or high PIC.

On each yearly anniversary of the dams DSAP approval, the dam owner must have a recognised engineer audit evidence of their compliance with the DSAP and prepare an annual dam compliance certificate. Either the owner, or the recognised engineer needs to provide a copy of the certified annual dam compliance certificate to Council.

Dam Register 

In accordance with the Building Act 2004, Nelson City Council as a regional authority is required to maintain a register of all dams in the Nelson region. This register enables a better understanding of Nelson’s dam portfolio and assists Council in providing appropriate support and resources to dam owners, including in emergency situations.

If you own a dam, you should check with Council to confirm that your dam is on the register.

Contact:  building@ncc.govt.nz

Dangerous Dams Policy 

Nelson City Council adopted a Dangerous Dams Policy in November 2006, as required by section 161 of the Building Act 2004.  The Policy outlines the approach and priorities Council will take in performing its functions in relation to dangerous dams in its region, and how the policy will apply to heritage dams.

Read the Nelson City Council Dangerous Dams Policy 2006

With the commencement of the Building (Dam Safety) Regulations 2022, Council intends to review its policy to include earthquake-prone dams, and flood-prone dams in due course.

Links 

Dam Safety Frequently Asked Questions (courtesy of Waikato Regional Council)

Potential Impact Classification (PIC) checklist for dam owners (MBIE website)

Measuring and calculating the height and volume of agricultural dams, and other resources (MBIE website)