Standards New Zealand has recently released the draft revised standard DZ6808: Acoustics – Wind farm noise (Draft Standard) for public submission. When approved, this standard will replace the existing standard NZS6808:1998 Acoustics – the assessment and measurement of sound from wind turbine generators (referred to in this article as the 1998 Standard).
Why was the 1998 Standard reviewed?
The 1998 Standard has attracted considerable comment in Environment Court and local authority hearings of wind farm applications, including in decisions such as Meridian Energy Limited v Wellington City Council* and Motorimu Wind Farm Limited v Palmerston North City Council**. In both cases wind farm opponents questioned the relevancy of the 1998 Standard, and the degree of protection it provided. The Environment Court in both instances imposed conditions (or the applicant agreed to the imposition of conditions) which required the wind farm to comply with noise limits which were more stringent than those in the 1998 Standard. The imposition of more stringent noise levels in these cases may have created an expectation within communities that such conditions (termed "sub-6808 conditions") were necessary in all cases. This created uncertainty for wind farm developers in the development and assessment of their projects.
The 1998 Standard was written prior to significant wind farm development in New Zealand. Scoping meetings and workshops held over the last few years, and involving a range of stakeholders, found that while the basic methodology of the 1998 Standard was robust, it should be revised to include numerous refinements and enhancements developed over the decade since the 1998 Standard was prepared.
How does the Draft Standard differ from the 1998 Standard?
The Draft Standard retains the primary noise limit in the 1998 Standard of background sound level plus 5dB, or a level of 40dB L90, whichever is the greater. This primary noise limit continues to apply at every point within the notional boundary of noise sensitive locations such as residences.
The Draft Standard also provides a secondary noise limit, which should only be considered in particular circumstances, including where evening or night time background sound levels are very low, or where objectives, policies or rules in a district plan promote a higher degree of protection of amenity in the particular location of the development, when compared to the district generally. The secondary noise limit is background sound level plus 5dB, or 35dB L90, whichever is the greater.
The Draft Standard clarifies a number of matters upon which it has been necessary to present evidence in recent hearings for wind farm resource consent applications.
Matters of clarification include:
- The noise limits recommended in the Draft Standard balance the need to avoid disturbance to people living in the vicinity, with the need to provide for a source of renewable energy. This contrasts with statements in the 1998 Standard that recommended noise limits were "appropriate", without further explanation;
- Definition of noise sensitive activities and locations;
- That audibility is not an appropriate basis for setting noise limits;
- Noise limits for wind farms in district plans should be based on those recommended in the Standard;
- The primary noise limit should provide a satisfactory level of protection against sleep disturbance, and is also appropriate for protecting the health of residents and maintaining reasonable amenity for most noise sensitive locations;
- The primary noise limit should always apply during day time and for higher wind speeds;
- Wind farm noise limits should not be set lower than 35dB L90 at any time;
- The sound levels of wind farms developed in stages shall be compared against the background sound level which existed before the first stage of the wind farm was developed; and
- Wind speeds should be measured at hub height levels.
The Draft Standard also helpfully contains model consent conditions which are more simple than those recently imposed by the Environment Court and consent authorities. Model resource consent conditions are likely to be well received by the Environment Court, consent authorities, applicants and submitters alike. However, the first condition's requirement for noise measurements to be assessed "at any point within the notional boundary of any noise sensitive locations existing or for which a building or resource consent [application] had been filed" would benefit from further refinement. Such measurements would serve no purpose if building or resource consents were not in fact granted as a result of the applications described in the condition.
Room for improvement?
In respect of other matters, the Draft Standard could lead to confusion, and may benefit from comments to the Standards Authority. Examples of these matters include:
- The Draft Standard states that it is intended to "protect noise sensitive locations which existed, or for which building consent or resource consent application has been filed, at the time the application for resource consent or for a notice of requirement for a designation for a new or altered wind farm is filed". This explanation of the "existing environment" for the purposes of noise assessment is not wholly consistent with that generally applied by the Environment Court when considering effects on the environment;
- The Draft Standard requires an adjustment of plus 5dB to be applied to a wind farm which is "deemed subjectively to create sound with a clearly audible modulation". It is not clear who would deem such a condition to exist; and
- The Draft Standard introduces the concept of building vibrations induced by incident airborne sound (or "secondary vibration"). While the Standard states "such rattling is known to exacerbate annoyance", it does not require any prediction of vibration induced rattling, or set boundaries to avoid it occurring.
How to make comments
Copies of the Draft Standard can be downloaded from the Standards New Zealand website (www.standards.co.nz). Comments on the Draft Standard can be made online or by completing the forms included in the first few pages of the Draft Standard. Comments on the Draft Standard must be submitted by 30 April 2009.
If you would like to discuss the Draft Standard with us, or if you would like assistance with preparing your comments on the Draft Standard, we would be happy to assist.