How much noise do turbines generate?
The main source of sound from wind turbines is aerodynamic sound, which is created as air passes around the blades. This sound is heard as a swishing or whooshing near to the turbines. Turbines can also produce mechanical sound from the generator and gear box (if present), and adjacent to the turbine the electrical transformer can be heard.
At the typical distance of the nearest houses to a wind farm (500m to 1km) the overall sound is generally a bland indistinct low level sound, sometimes compared to the sound of waves on a beach.
When standing underneath or in the vicinity of the wind turbines (within approximately 100 metres) the sound levels are typically in the range of 55 to 60 dB, which is similar to sound levels experienced during normal conversation between people.
At the nearest houses (eg 500m to 1km) sound levels from wind farms are usually in the range of 35 to 40 dB outside houses. These sound levels outside houses are similar to the sound levels normally experienced inside a quiet library, or from people talking in hushed voices.
Does the geography of the area proposed for the turbines add to the noise they emit?
Topographic contours are integral to the acoustics computer model for the wind farm, and the interaction of sound waves with the ground between each wind turbine and each house is included in the calculations. At some frequencies the sound is partially absorbed by the ground, but at other frequencies it is amplified. These effects are included in sound level predictions.
Reflections from surrounding terrain in the wider area do not noticeably increase sound levels because of the increased propagation distance of sound travelling out to the valley side and back compared to the direct sound path, and losses due to absorption and scattering at the reflection from the valley side.
Also, the inclination of valley sides is such that sound is reflected predominantly upwards rather than down towards houses. Reflections from hillsides of impulsive or short duration sound are often clearly audible as echoes, but this does not relate to a significant increase in level for continuous wind farm sound.
In rural valleys people often refer to experiencing ‘amphitheatre’ effects. In many cases this relates to the fact that the area is quiet at times so sounds from surrounding activities are still audible at a significant distance. Another reason is that sheltered valleys can support the development of temperature inversions, under which condition sound propagation is enhanced. However, with respect to wind farms, strong temperature inversions only develop in stable air conditions which can only exist with low wind speeds when wind farms do not operate.
Is there a difference in decibel level and tone between 90m and 207m wind turbine blades?
Yes - There are differences between different size wind turbines. When comparing modern designs, a single large wind turbine produces more sound than a single small wind turbine. However, a single large wind turbine produces less sound than multiple small wind turbines that would be required to generate the same electrical power.
Wind turbine rotation speeds are limited by the speed of the blade tip. A larger wind turbine therefore rotates at a slower speed than a small turbine, altering the timing of the blade swish heard when standing close to turbines.
Noise effects vary between specific sites and are not universally better or worse with larger or smaller wind turbines.
What noise monitoring has been carried out?
In March 2017 monitoring was conducted at a property in Thorp Road and another in Rawhiti Road to gain an appreciation of the existing environment used in conjunction with site observations. Further baseline measurements for establishing noise limits will be required prior to construction, and compliance measurements will be required when turbines start operating. These additional measurements will be undertaken at three representative locations, which are proposed at three properties in Thorp, Rawhiti and Rotokohu Roads.
Were different wind conditions and weather factored into the noise readings?
Yes – sound level measurements are analysed relative to the measured wind speed and direction in each 10 minute period during the survey. This is required by NZS 6808.
Will an acoustics plan be prepared?
Prior to construction a prediction report in accordance with NZS 6808 will be prepared to confirm the sound from the final turbine type and layout (unless it is identical to the current assessment). A compliance assessment report will also be prepared once the wind farm is operating and will be submitted to the Council.
What impact will the turbines have on the ecology, fauna and birdlife in the area?
Environmental specialist, Kessels Ecology, was commissioned to undertake an ecological effects assessment of the proposed Kaimai wind farm and surrounding locality to determine existing ecological features and their relative sensitivity to the construction and operation of the proposed wind farm.
The field work for the investigation was undertaken from 2009 to 2017 enabling data to be collected across multiple years on the distribution and habitat utilisation of the locality by birds and bats. Further desktop analysis was undertaken to determine the effects of the proposal on aquatic freshwater biota, indigenous vegetation, lizards and terrestrial invertebrates. Below is a summary of the investigation –
Effects on Vegetation
The wind farm area can generally be described as a mosaic of rolling pasture land with a number of exotic plantations and indigenous forest remnants scattered throughout. Some 72% of the site is covered in pasture. Smaller stands of secondary broadleaved forest are mainly present within the gully systems in the northern half of the site, while larger areas of logged tawa forest remain along the eastern margin of the site (i.e. the Kaimai Ranges), as well as in the southern extent of the site and near the quarry at the north-western margin of the site.
While indigenous forest and scrubland is situated within 100 m from the edge of some of the turbine locations, since all the centres of the turbines are located in the pastoral land no indigenous vegetation will be removed in the turbine footprint. No ecologically significant indigenous vegetation or nationally threatened plant species would be affected by the proposal.
The introduction of new weeds, diseases and the spread of existing weed species will need to be managed to protect the ecological health of the existing indigenous vegetation remnants in the locality.
All machinery and aggregate brought onto site will need to be cleaned, or otherwise guaranteed free of attached seed or plant matter before being brought on to site.
Provided due care and initial weed control is carried out as and when required, it is expected that the pasture or indigenous scrubland species will quickly gain a foot-hold and dominate vegetative cover along access road batters and cuts.
Effects on Freshwater Aquatic Habitats
No fish or aquatic macroinvertebrate habitats would be adversely affected provided appropriate sediment control measures are adopted. No upgrades to existing access stream crossing are proposed with the current roading design. Although water abstraction requirements have not be defined at this point in time, abstraction points should result in no more than minor adverse effects on in-stream biota provided suitable storage and/or non-fully allocated water sources can be devised and found.
Sediment control measures include, but are not restricted to, controlling run off, the prevention of slumping of batters, cuts and side casting, maintain slope stability and contingency measures for heavy rainfall events.
Effects on Lizards, Frogs and Terrestrial Invertebrates
As no ecologically significant indigenous vegetation will be disturbed during the construction phase adverse ecological effects on lizards and indigenous terrestrial invertebrates is likely to be minimal. However, it is possible that areas of non-ecologically significant vegetation (both exotic and indigenous) cleared or trimmed for infrastructure development or tower placement will include lizard and invertebrate habitat.
The consequential relatively minor adverse effects on these fauna groups can be managed through appropriate mitigation and monitoring measures. Details of these measures can be dealt with as part of the consent conditions.
Effects on Birds
According to international best practice guidelines a summary of the main bird habitat areas which should be avoided when locating a wind farm are: (1) Areas with a high density of wintering or migratory waterfowl and waders where important habitat might be affected by disturbance or where there is potential for significant collision mortality; (2) Areas with a high level of raptor activity, especially core areas of individuals breeding ranges and in cases where local topography focuses flight activity which would cause a large number of flights to pass through the wind farm; and (3) Breeding, wintering or migrating populations of less abundant species, particularly those of conservation concern, which may be sensitive to increased mortality as a result of collision.
The main bird groups impacted by wind farm developments internationally have been swans, geese, ducks, waders, gulls, terns, large soaring raptors, owls and nocturnally migrating passerines. Most resident bird species within the study site are common and widespread with the potential exceptions of New Zealand pipit, North Island kaka and New Zealand falcon, which are all found in the local area. There is a risk of collision with the turbine blades, especially along the forest edge. It is possible that New Zealand falcon and kaka will suffer occasional strike, particularly by the turbines along the forest edge of the Kaimai-Mamaku Conservation Park. Australasian bittern may be also be at risk from strike while moving between the Bay of Plenty and Kopuatai Peat Dome. However; of these species, only pipit was detected during the bird surveys or by the acoustic surveys, so while non-detection does not necessarily mean these birds are absent from the locality, it does suggest that they may be present in low densities. While the ability of these key forest and wetland bird species to adapt to the turbines and become accustomed to associated noise and movement is likely, and the birds should be able to fly around the turbines to gain access to other remnant bush areas within the locality, there is a likelihood that strike will occur from time to time.
There is insufficient data for this site to determine the strike level, but modelling and carcass searches at other similarly situated New Zealand wind farms suggest strike rates will be low. Nonetheless, the local effects of this mortality may be more than minor on threatened species, so some form of offset mitigation, such as a contribution to local animal pest control to increase bird productivity, is recommended.
The impact of the wind farm on migratory birds is dependent on any flight path these species may take between key habitats in the Bay of Plenty and Firth of Thames. Wader and shorebird species, such as bar-tailed godwit, wrybill and South Island pied oystercatcher, may move between the Firth of Thames and Tauranga Harbour on a regular basis and in doing so traverse the proposed windfarm footprint. The sound recorders detected two flocks of South Island pied oystercatchers crossing the proposed wind farm site on one occasion in January 2013, from a total recording effort of some 4,000 hours. These detected South Island pied oystercatchers were crossing the southern section of the windfarm over the Kaimai range. This indicates that the site is likely part of a seasonal commuting route for waders between the Haruaki Gulf and Tauranga Harbour.
Initial strike risk analysis at similar New Zealand sites indicates that turbine strike is possible for wader species and it will be in the range of less than 2-5 birds per annum for the proposed Kaimai wind farm. This level of strike risk is considered to have a minor adverse effect on the target shorebird species. However, given that several species are threatened, such as wrybill, offset mitigation may be required to compensate for any residual adverse effects on wader bird species. Quantification of this offset can be addressed at the consenting stage, but could involve a contribution to conservation activities by community groups at Miranda, which is a key site for international and national wader birds.
Effects on Bats
The nationally threatened North Island long-tailed bat is known to be present within the Kaimai Ranges and was detected during the surveys for this proposal. The survey results showed longtailed bat activity during 4-17 January 2013, and from 22 September to 27 October 2015 at the study site. In the 2015 survey 63% (eight) of all of the surveyed sites contained long-tailed bats, while in the 2013 bat survey 55% (11) of the sites contained bats. In total 59% (19) of the surveyed sites detected bats. No publicly accessible studies have investigated the impacts of wind farms on the spatial use of either of New Zealand’s native bat species. Therefore, it is not clear whether avoidance behaviour occurs in either native bat species.
Based on review of international studies it is considered possible that long-tailed bats will suffer mortality as a result of interactions with the turbines. Thus, bats are considered to be at moderate risk of being killed or injured by turbine strike at this proposed wind farm site. A combination of habitat restoration and pest control would enhance the local North Island longtailed bat population, producing a healthy source population which could mitigate against any declines at the proposed wind farm site.
Avoidance, Remediation and Mitigation Recommendations
The proposed Kaimai wind farm is situated within a largely pastoral environment, heavily modified by human activities and animal pests. No ecologically significant or legally protected natural features will be directly affected by the proposed wind farm. However, there are several threatened birds and one bat species which could be adversely affected by the turbines in the form of turbine blade strike. The biodiversity consequences of this risk are low to moderate at a local level, and the effects are likely to be minor at a regional, national and international scale.
It is recommended that measures are taken to avoid, remedy or mitigate the adverse effects of turbine strike on these key animals and their habitats, as well as address the localised potential adverse effects associated with construction. A range of measures that will avoid, remedy or mitigate the adverse effects of the project (inclusive of the wind turbines, access roads and the transmission lines) are required. They should include:
- Ensuring all aspects of the construction and operation of the wind farm minimise any potential adverse effects associated with indigenous flora and fauna habitat disturbance, sediment runoff, water abstraction and stream crossings (if any);
- Preparation and implementation of a mitigation package to compensate for potential turbine strike on key indigenous fauna which incorporates enhancing productivity of the target species through ongoing animal pest control and ecological enhancement of targeted natural features; and
- Monitoring of key fauna species, as well as carcass searches under the operational turbines, for a specified period, in order to ensure that the risks associated with the operation of the wind farm are low and to allow for adaptive management risk minimisation contingencies if required.
What impact have windfarms had on property values where they have been established in New Zealand?
Research carried out by Colliers International indicates that in New Zealand thus far, there will be no or negligible long term ongoing negative value impacts on the values of rural properties surrounding the proposed Kaimai Wind Farm, caused by the wind farm being visible to the rural properties or parts of properties.
In summary, studies have shown that there may be a potential difference in the impact on property values arising from the proximity of wind turbines, depending on the property type. Rural properties have been shown to be least affected of all; and in some studies affected positively. Lifestyle blocks generally occupied by city office workers may potentially be affected if turbines are within hearing distance or very close to dwellings, at wind farms close to cities. At some other lifestyle locations, however, not near cities; where wind farms have been established nearby, such as at Te Apiti near Palmerston North, no fears over value erosion have arisen or been expressed in the resource consent process. It appears (and this is borne out from anecdotal experience) that residents largely support the environmental benefits derived from sustainable electricity generation.
In conclusion, Colliers’ introductory study has confirmed earlier findings that there are no discernible negative value impacts on rural property values caused by wind farms being visible to parts of properties.
What is the predicted traffic use on local roads?
Kaimai Wind Ltd is proposing that extra-heavy transportation be limited to one route – Rawhiti Road – to contain effects and need for bridge and roadside upgrades.
Eight to 16 tonne truck units may use Rotokohu Road and Rawhiti Road.
Lighter traffic – utes, cars and light trucks (less than 8 tonne) – may use Rotokohu Road which is convenient for staff accommodation and supply of equipment from outlets in Paeroa.
How will the local community benefit from the establishment of the windfarm?
We expect a good level of commerce will be generated in Paeroa during pre-construction, construction and commissioning of the wind farm.
At least two staff will reside in Paeroa and we will also establish a warehouse in the town to store key parts and consumables. There will therefore be advantage to the local community from personnel living in town and from local people being employed and trained for the wind farm.
The rating base for the Hauraki District Council will also increase with potential benefit via council services.
Aren’t there more remote locations where the windfarm could be established?
There are lots of remote locations in New Zealand, however the main constraint, when it comes to developing a wind farm, is remoteness from a grid connection and transport routes. To justify a remote wind farm (which has a high cost of grid connection and roads) wind farm projects have to be larger – often much larger – eg the now cancelled HMR project on the west cost of the Waikato. A wind farm in New Zealand needs to of moderate scale (to fit into a demand gap in the market) and needs to be close to roads and grid connection. It also needs to have an excellent wind resource and be consentable.
How will you keep the local and wider community informed?
Communication is a two-way path – the first part is ours, providing you with regular updates on what is happening so you feel informed. The second part is yours – if you have questions or concerns, let us know so we can answer them.
One tactic won’t achieve the level of engagement we want with the local community so we will be using a variety – from regular update letters to neighbours, to regular updates on our website, public meetings and via local media. Our aim is to be as transparent as possible so you understand what is proposed for your district.
Will the turbines be lit at night?
The wind farm is likely to have suitable lighting to comply with the requirements of CAANZ Rule Part 77.21(d) and appendix B and marked on aeronautical charts. This would be a CAANZ decision.
Do you plan to extend the windfarm beyond the current proposal?
There are currently no plans to extend the wind farm beyond the current proposal.
Will public meetings be held to provide local people with an opportunity to have their questions answered?
Public meetings have a place in public consultation and engagement – not simply as a means for us to tell you about the project, but to provide you with an opportunity to meet the people behind the project, and have your questions and concerns answered. We have conducted a few over the last year, most recently with residents of Rotokohu and Thorp Roads. We have also met – and will continue to meet – with residents in their own homes so we can experience and understand their concerns.
Are you talking with local Iwi?
Yes, we are consulting with local Iwi.
The Kaimai Range is popular with paragliders – what steps are you taking to talk to, and answer, their concerns?
We have had a number of conversations with the local Soaring Club and with commercial and recreational flyers and, as a result, reduced the number of turbines from 26 to 24 to accommodate flight paths. We would also consider shutting down specific turbines during gliding competitions.
Peet Aviation also conducted a comprehensive aviation report which concluded that the proposed wind farm will not represent a physical obstacle to glider operations over the proposed site. Likewise, turbulence and wind shear will not be an issue when wind speeds in the area are approximately 16 knots, which is the norm. Glider operations over the proposed site may, however, be affected when wind speeds are more than 20 knots – although this would account for potentially 15% of the time, and needs to be considered against the fact that glider activity would remain viable and subject to pilots conducting flights ina safe and secure manner at an appropriate altitude.
What considerations are you able to give for people who have an emotional or special affiliation with the area proposed for the turbines?
We understand that people may have emotional connections to the land that we are proposing for the wind farm. If you, or someone you know, has particular concerns about any area of the proposed windfarm (see attached map), then we want to know. Please contact us via the website.
What is the proposed timeline for the proposal?
The consent application has been lodged with the Hauraki District and Waikato Regional Councils and was notified in December 2018. This enabled the sharing of a range of detailed reports and analyses on the project empowering the public to make submissions on the proposal.
Submissions closed on 31 January 2019. The next steps in the process are now being finalised but will include some pre-hearing meetings to try to reach some agreement and narrow down the issues to be heard at a later hearing. The pre-hearing meetings are expected to be held in July. The hearing itself is expected to take place in the fourth quarter of the year and will give submitters the opportunity to present their views verbally to independent commissioners who will be appointed by both councils to make a decision on the proposal.
You can check out the application here: https://www.hauraki-dc.govt.nz/services/resource-consents/kaimai-wind-farm-project/
Got any questions?
If you have any questions about any aspect of the proposal to construct and operate a wind farm on the lower Kaimai Ranges, please let us know – simply fill out the form on the website www.kaimaiwind.nz and we will respond to you directly and include your question and our answer in this Q&A.