Dam Safety Scheme - Guidance for regional authorities and owners of large dams: Navigating the Dam Safety Scheme

4.1 Which dams are affected by the Scheme?

The Scheme only applies to large dams. A large dam is defined by section 7 as being a dam that retains three or more metres depth, and holds 20,000 or more cubic metres volume of water or other fluid. The types of dam that are included are those caught by the definition of 'dam' in section 7 of the Act:

(a) means an artificial barrier, and its appurtenant structures, that -

(i) is constructed to hold back water or other fluid under constant pressure so as to form a reservoir; and

(ii) is used for the storage, control, or diversion of water or other fluid; and

(b) includes - 

(i) a flood control dam; and

(ii) a natural feature that has been significantly modified to function as a dam; and

(iii) a canal; but

(c) does not include a stopbank designed to control floodwaters. 

The definition of dam includes a variety of terms. To assist with interpreting these terms, there is a glossary of terms in Appendix D.

A large dam has roughly the capacity of eight Olympic-sized swimming pools, or a rugby field with water 3m deep - that is, up to the crossbars of the goalposts.

4.2 Dam structures

There are a variety of structures could be affected by the Scheme, including, but not limited to, the following examples:

You can use the following formula to calculate the approximate volume of the reservoir behind a dam. Otherwise, dam owners may get a suitably qualified professional engineer to check the size.

Note: volume is based on its maximum reservoir capacity, even if it rarely meets this full capacity.

4.3 Classifying a large dam affected by the Dam Safety Scheme

If a dam meets the definition of a large dam under the Act, the owner of the dam will be affected by the Scheme.

Under section 134 of the Act, a large dam is required to be classified. The owner of a large dam needs to classify their dam and have this classification certified by a Recognised Engineer (as defined in section 149 of the Act) as either having a low, medium or high potential impact.

The classification of a dam reflects the potential impact a dam failure could have on people, property and the environment.

Initially, the dam owner may decide which classification is appropriate for their large dam, but that decision must be confirmed by a Recognised Engineer. The Recognised Engineer must audit the dam owner's classification against the classification criteria in the Regulations and, if they agree, they have to give the dam owner a certificate confirming the dam's PIC.

4.4 Methodology and guidance for classifying a large dam

The Regulations set out the methodology for classifying dams (see Regulation 4). The following tables are used in the Regulations for classifying a large dam (see Schedule 1 of the Regulations).

Schedule 1. Dam Classification

Table 1. Determination of Assessed Damage Level

Damage Level	Specified categories
		Critical or major infrastructure
	Residential houses1	Damage	Time to restore to operation3	Natural environment	Community recovery time
Catastrophic	More than 50 houses destroyed	Extensive and widespread destruction of and damage to several major infrastructure components	More than 1 year	Extensive and widespread damage	Many years
Major	4 to 49 houses destroyed and a number of houses damaged	Extensive destruction of and damage to more than 1 major infrastructure component	Up to 12 months	Heavy damage and costly restoration	Years
Moderate	1 to 3 houses destroyed and some damaged	Significant damage to at least 1 major infrastructure component	Up to 3 months	Significant but recoverable damage	Months
Minimal	Minor damage	Minor damage to major infrastructure components	Up to 1 week	Short-term damage	Days to weeks

Notes

1. In relation to residential houses, destroyed means rendered inhabitable.

2. Includes:

(a) lifelines (power supply, water supply, gas supply, transportations systems, wastewater treatment, telecommunications (network mains and nodes rather than local connections)); and

(b) emergency facilities - (hospitals, police, fire services); and

(c) large industrial, commercial, or community facilities, the loss of which would have a significant impact on the community; and

(d) the dam if the service the dam provides is critical to the community and that service cannot be provided by alternative means.

3. Estimated time required to repair the damage sufficiently to return the critical or major infrastructure to normal operation.

Table 2. Determination of Dam Classification

Assessed Damage Level	Population at risk (par)
		Critical or major infrastructure
	0	1 to 10	11 to 100	More than 100	Community recovery time
Catastrophic	High potential impact	High	High	High	Many years
Major	Medium potential impact	medium/High (see note 4)	High	High	Years
Moderate	Low potential impact	Low/Medium/High (see notes 3 & 4)	Medium/High (see note 4)	Medium/High (see notes 2 & 4)	Months
Minimal	Low potential impact	Low/Medium/High (see notes 1,3 & 4)	Low/Medium/High (see notes 1,3 & 4)	Low/Medium/High (see notes 1, 3 & 4)	Days to weeks

Notes.

1. With a PAR of 5 or more people, it is unlikely that the potential impact will be low.

2. With a PAR of more than 100 people, it is unlikely that the potential impact will be medium.

3. Use a medium classification if it is highly likely that a life will be lost.

4. Use a high classification if it is highly likely that 2 or more lives will be lost.

The following provides more information about the previous tables and how to use them.

The tables use a number of technical terms. To assist with interpreting these terms, there is a glossary of terms in Appendix D.

Table 1: Determination of Assessed Damage Level

The damage level needs to be assessed by considering the impact on:

• residential houses
• critical and major infrastructure (both damage caused and estimated time to restore to normal operation)
• natural environment
• community recovery time.

a) The dam owner must determine and/or estimate the damage that would be caused by an uncontrolled release of the reservoir when full due to a dam breach - that is, if the dam fails, what would likely occur?

b) The dam owner may do the assessment themselves and use a Recognised Engineer to verify the classification, or the dam owner may use a Recognised Engineer to handle the whole classification process. The Recognised Engineer must be either a Category A or Category B Recognised Engineer, as discussed in 4.10 of this guide.

In some situations an estimate of flood areas may be carried out using the downstream topography - ie, valley shape and slope - as it may be obvious whether the flow is going to impact on houses, infrastructure, or the natural environment, or find its way to a larger water course and not cause much damage. For straightforward dam layout and topography, it will be a matter of examining where the water might flow using an on-site assessment. If required, a suitably qualified professional engineer will be able to create an inundation/flood map.

Note: More complex layout or topography may require engineers experienced in hydraulic modelling to map the inundation level. Once the flood map has been created, it can be used to assist in classifying the PIC of the large dam.

d) The damage level is determined by assessing whether the damage level in each of the specified categories is catastrophic, major, moderate or minimal, and then selecting the highest damage level.

Example: An assessment determines that in the event that a particular dam failed, it would result in:

• three houses becoming uninhabitable with the likely loss of two or more lives
• minor damage to a state highway
• flooding of a protected ecosystem resulting in destruction of the habitat of endangered species
• extensive damage to the natural environment and costly restoration
• it would take several months for the community to recover.

In this example, the damage to residential houses is moderate, damage to critical and major infrastructure is minimal, and time for the community to recover and damage to the natural environment is major. The damage to the natural environment is the highest out of all of the columns, so the assessed damage level is 'major'.

Table 2: Determination of Dam Classification

Dams must be classified as high, medium or low PIC. Using Table 2, the classification depends on the population at risk (PAR) and on the assessed damage level (as determined in Table 1).

The assessor determines:

(1) how many people would likely be affected by inundation greater than 0.5 metres in depth; and
(2) how many lives would be lost (this can be done at the same time as estimating the assessed damage level).

Example: In the example above the three houses indicate a PAR in the range of 1-10. With a 'major' damage level from Table 1, the dam could be either medium or high PIC from Table 2. The location of the houses indicates that two or more lives are likely to be lost. On the basis of Note 4 in Table 2 the dam is classified as high PIC. This assessment is submitted to a Category A Recognised Engineer for review and certification, before being submitted to the regional authority.

The PAR and the potential damage must be determined on the basis of a breach or failure of the dam. For this purpose, a breach or failure of a dam occurs when it is at full service level and all retained fluid is released over a short period of time. The PAR is determined as those likely to be affected by a flood greater than half a metre deep. When considering PAR, the following issues should be taken into account:

• groups of dwellings
• camping areas and occupancy times
  allowance for temporary populations (eg, fishermen, bushwalkers, birdwatchers, picnickers)
• river crossings and bridges
• the number of people using nearby schools, hospitals and other institutions (eg, prisons) as well as commercial and retail areas.

4.5 Submission of the classification certificate and registration of dams

The owner of an existing large dam will first need to submit the classification certificate to their regional authority within three months of the Regulations coming into effect (that is, by September 2010). Owners of new dams will need to submit the classification certificate to the regional authority within three months of the dam being commissioned.

A Dam Classification Certificate is in Appendix A. You can also get one from the Department's website: http://www.dbh.govt.nz/bofficials-dam-safety

Once the regional authority has received the Dam Classification Certificate, the classification of the dam is placed on the regional dam register. For more information on this, refer to sections 134 to 139 of the Act.

An owner of a large dam who fails to comply with section 134 of the Act is liable for a fine not exceeding $20,000 or an infringement fee¹ of $500.

4.6 When to review the classification

An owner of a large dam must review the dam’s classification and resubmit it with a Recognised Engineer’s certificate in accordance with section 139 of the Act, as follows:

• within five years after the regional authority approves the classification and at intervals of not more than five years
• after the first review, at intervals of not more than five years
• if at any time building work that requires building consent is carried out on the dam, which results in or could result in a change to the potential failure impact on people, property, or the environment.

4.7 Dam Safety Assurance Programme

Sections 140 to 148 of the Act outline the requirements for a Dam Safety Assurance Programme. The owner of a medium or high PIC dam is required to prepare a Dam Safety Assurance Programme.

The purpose of a Dam Safety Assurance Programme is to assist the owner of a large dam to ensure good safety management of the dam through the life of the structure and to manage the resolution of any potential deficiencies that may arise. A Dam Safety Assurance Programme is basically a document that sets out the dam owner’s procedures for checking the safety of their dam, including an emergency action plan, and a plan for repairing any non-urgent deficiencies with their dam.

The owner of a medium or high PIC large dam must:

• prepare, or arrange for the preparation of, a Dam Safety Assurance Programme for the dam (using the form in the Regulations)
• have the Dam Safety Assurance Programme audited by a Category A Recognised Engineer
• submit to the appropriate regional authority the audited Dam Safety Assurance Programme within one year (if a high PIC) or two years (if a medium PIC dam) of the dam’s classification
• have the Dam Safety Assurance Programme audited and reviewed within five years (if a high PIC dam) or ten years (if a medium PIC dam) of the regional authority originally approving the Dam Safety Assurance Programme, and every five years thereafter.

A Dam Safety Assurance Programme must be appropriate for the type, size and classification of a dam.

A Dam Safety Assurance Programme must contain the following:

(a) requirements for and frequency of, routine visual inspections, instrument monitoring, data evaluation, and reporting to the large dam owner
(b) requirements for annual dam safety reviews
(c) requirements for comprehensive dam safety reviews
(d) details of an emergency action plan
(e) requirements for inspection of appurtenant structures, including testing of gates and valves that contribute to reservoir safety, and
(f) procedures for the investigation, assessment and resolution of dam safety deficiencies.²

The Dam Safety Assurance Programme must be consistent with the New Zealand Society On Large Dams’ (NZSOLD) New Zealand Dam Safety Guidelines (2000). The NZSOLD Dam Safety Guidelines (2000) can be viewed on NZSOLD’s  website: http://www.ipenz.org.nz/nzsold/.

The Dam Safety Assurance Programme should be structured so that the assurance of safe performance of the dam is achieved, while allowing enough flexibility for unforeseen disruptions.

The Dam Safety Scheme is one of strict compliance. It does not allow for partial compliance with the Dam Safety Assurance Programme. Accordingly, when designing a Dam Safety Assurance Programme, the dam owner and Recognised Engineer should ensure that the programme is flexible enough to reflect the risk that routine surveillance, monitoring and inspection can potentially be disrupted. This can delay planned Dam Safety Assurance Programme activities and the timeframe to ensure full compliance with the annual Dam Compliance Certificate. Disruptive factors to take into account may include:

• high or low inflows
• extreme weather conditions
• staff leave
• resource availability
• acts of God
• how it will affect ensuring full compliance with the annual Dam Compliance Certificate.

The Dam Safety Assurance Programme form is in Appendix B or on the Department’s website:  www.dbh.govt.nz/bofficials-dam-safety

Once the Dam Safety Assurance Programme form has been prepared and audited by a Category A Recognised Engineer, it must be sent to the regional authority. The regional authority must approve the form, unless it considers on reasonable grounds that the engineer who audited and signed off on the Dam Safety Assurance Programme is not a Category A Recognised Engineer.

The timeframe for submitting a Dam Safety Assurance Programme and form is one year after the regional authority approved the classification for a high PIC dam and two years for a medium PIC dam.

A medium or high PIC large dam owner who fails to submit a Dam Safety Assurance Programme by the statutory date required is liable for a fine not exceeding $20,000 or an infringement fee of $500.

If a regional authority refuses to approve the Dam Safety Assurance Programme, it must direct the dam owner to have the Dam Safety Assurance Programme audited by a Recognised Engineer.

The dam owner will then have 15 working days, unless a later date is agreed on by the regional authority, to have their Dam Safety Assurance Programme re-audited and submitted with the Dam Safety Assurance Programme form. Failure to do so may result in a fine of up to $10,000 or an infringement fee of $250.

Once the Dam Safety Assurance Programme has been approved by the regional authority, the dam owner must keep the Dam Safety Assurance Programme document either:

• on the dam, or
• in another building in the region of the regional authority, or
• in some other place agreed on by the owner of the large dam and the regional authority.

The Dam Safety Assurance Programme document must be available for inspection by the regional authority and any person or organisation that has a right to inspect the dam under any Act.

4.8 Review of a Dam Safety Assurance Programme

Section 146 of the Act states that the owner of a high PIC dam must review their Dam Safety Assurance Programme:

• within five years of it being approved by the regional authority
• after the first review, at intervals of no more than five years.

The owner of a medium PIC dam must review their Dam Safety Assurance Programme:

• within 10 years of it being approved by the regional authority
• after the first review, at intervals of no more than five years.

Owners of large dams must, at all times, review their Dam Safety Assurance Programme whenever building work is done on the dam that requires a building consent and that could result in a change to the PIC. Owners of large dams that are earthquakeprone or flood-prone must also review their Dam Safety Assurance Programme upon the request of the relevant regional authority.

4.9 Annual Dam Compliance Certificate

Section 150 of the Act states that every owner of a dam for which a Dam Safety Assurance Programme has been approved must provide the regional authority with an annual Dam Compliance Certificate on each anniversary of their Dam Safety Assurance Programme having been approved. The certificate must include confirmation from a Category A Recognised Engineer that all procedures in the Dam Safety Assurance Programme have been complied with during the previous twelve months.

By submitting the annual Dam Compliance Certificate to the regional authority, the owner provides ongoing evidence of doing surveillance and maintenance in line with the approved Dam Safety Assurance Programme.

An owner may face an infringement fee of $250 if they fail to display an annual Dam Compliance Certificate, under section 150 of the Act. An owner of a large dam may also face an infringement fee of $1000 if they knowingly:

• display a false or misleading annual Dam Compliance Certificate
• fail to display an annual Dam Compliance Certificate that is required to be displayed under section 150 of the Act
• displays an annual Dam Compliance Certificate otherwise than in accordance with section 150 of the Act.

The offences listed above also carry a fine of up to $5,000.

4.10 Category A and B Recognised Engineers

Compliance with the Dam Safety Scheme requires the exercise of professional knowledge and judgement. Under the Scheme, the classification of dams and Dam Safety Assurance Programmes must be certified by a Recognised Engineer, a term specific to the Act. These requirements aim to ensure that a large dam is correctly classified and that a Dam Safety Assurance Programme is appropriate to the dam and meets the prescribed criteria and standards for dam safety.

A Recognised Engineer is someone who has no financial interest in the dam, is registered under the Chartered Professional Engineers of New Zealand Act 2002, and meets the competencies listed in the Regulations.

There are two categories of Recognised Engineers, Categories A and B.

Category A Recognised Engineers have specific dam engineering and safety assurance competencies. Category A Recognised Engineers may:

• certify dam classifications
• certify Dam Safety Assurance Programmes
• certify annual Dam Compliance Certificates for dams.

The Institution of Professional Engineers New Zealand (IPENZ) oversees the assessment process. IPENZ uses a a pool of assessors to assess engineers on the requirements of a Category A Recognised Engineer. Engineers may be assessed against some or all of the following competencies:

(a) geotechnical principles
(b) design principles including structural geotechnical seismic hydrologic and hydraulic principles
(c) dam construction techniques
(d) operation and maintenance of dams
(e) surveillance processes
(f) response to dam safety issues
(g) emergency planning
(h) emergency response
(i) resolution of potential dam safety deficiencies
(j) dam safety critical plant systems.

A Category A Recognised Engineer is assessed by the Competency Assessment Board as demonstrating that he or she is able to practise competently in the area of dam safety engineering to the standard of a reasonable professional engineer practising in the area.

Category B Recognised Engineers have general civil engineering ability and experience and may only certify the classification of low PIC dams. Unlike Category A Recognised Engineers, Category B Recognised Engineers are not required to be formally assessed.

A Recognised Engineer must comply with the Chartered Professional Engineers of New Zealand Code of Ethical Behaviour. A Recognised Engineer must also comply with Chartered Professional Engineers of New Zealand Rules (No. 2) 2002. These state that a chartered professional engineer must not misrepresent his or her competence and only do engineering activities within his or her competence.

IPENZ will manage an online list of Recognised Engineers. The list will have contact details for Recognised Engineers who have agreed to make their details available. The list of Recognised Engineers will be updated as the Scheme progresses. This list can be found at:

www.ipenz.org.nz  

For more information on who is a Recognised Engineer, refer to section 149 of the Act.

4.11 Timeline for implementation of the Dam Safety Scheme

4.12 Register of large dams

Section 151 of the Act requires each regional authority to establish and maintain a register of all large dams in its region.

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1 Under Section 372 of the Building Act 2004, an infringement notice may be served on a person if an enforcement officer (a) observes the person committing an infringement offence, or (b) has reasonable cause to believe that an infringement offence is being or has been committed by that person. The Building (Infringement Offences, Fees, and Forms) Regulations 2007 are available from http://www.dbh.govt.nz/bofficials-bca or free phone 0800 242 243.