The recent Scottish Natural Heritage (SNH) draft guidance on wind farm repowering, published in June 2018, is out for consultation until 31st August. Jason McGray, TNEI’s environment and consents lead, sets out his thoughts on the approach to assessment that is proposed and implications for commercial scale wind farms.
The draft guidance specifically focuses on repowering existing operational wind farms. It does not cover life extension or increasing the design envelope of consented but unbuilt schemes. SNH naturally focuses on its areas of responsibility; landscape and ecology, although the document is likely to provide guidance on the approach to assessment that could be adopted by other topic areas. While the guidance will apply only to Scotland, it is likely that, in the absence of anything similar, the determining authorities in England, Wales and Ireland would look to it as has been the case with previous guidance, such as for production of visualisations and ornithological survey methods.
Establishing the Landscape and Visual Baseline
The key question that is the focus of the draft is how to establish the baseline for assessment. The SNH proposed approach is to adopt a baseline for assessment where the current operational wind farm has been decommissioned in line with a decommissioning statement, if one is available. The rationale, set out in Annex A of the guidance, is not unreasonable. SNH is seeking to avoid “‘gap assessments’ where the findings of the Landscape and Visual Impact Assessment (LVIA) are limited to the difference in the effects that would be experienced between the development of the repowered wind farm and the existing operational scheme. In other words, it seeks to avoid impact creep.
Fundamental to this approach is the assumption that the most likely evolution of the current baseline that includes the operational wind farm, is its decommissioning at the end of its consented life. As the majority of wind farms have time-limited consents (something that needs to be addressed for future decision making) it is reasonable to assess a scenario where decommissioning takes place at the end of that consented period. Where there is a decommissioning plan in place then it is also reasonable to assume that this is followed. In practice however, the majority of older wind farms do not have an agreed decommissioning plan and so it will be necessary to make assumptions based on current common practice.
Where the operational wind farm is not at the end of its consented life however, consideration of the baseline should ideally take into account the remaining life of the existing wind farm and other changes that might occur during that time, and then its decommissioning. The temporal aspect is tricky. What if a wind farm consent has 10 years left and an application is made for a 25-year repowering project? Should assessment factor in the existing wind farm remaining in place for the next 10 years and then assume that restoration would occur such that the change in effects due to the repowered scheme occurs in 10 years from now and lasts for a further 15? The argument may be made that this is unrealistic and would lead to under assessment of effects as repowering is proposed now and must be assessed from day one. By the same logic the reality would be that the operational wind farm would be replaced very quickly by the new repowered scheme and so the artificial decommissioned baseline will result in exaggerated effects over the next 10 years. Perhaps the most accurate assessment would be one that presents a “‘gap assessment’ for effects that would last for the remaining 10-year life of the operational consent and then the level of those effects would increase and be considered to occur at the point that the existing wind farm should have been decommissioned for a further 15 years.
The wind energy industry needs to avoid any situations where decision makers feel that landscape effects are acceptable for the next 10 years but then unacceptable beyond that and could be tempted to seek shorter time limited consents. For that reason, assessing repowering schemes as proposed by SNH seems to be a safer option.
Cumulative Development
There is also a question about what happens to cumulative wind farm developments that would overlap the repowering of the project in question. Consistent application of the proposed guidance would mean that you assume that the current operational wind farms in the surrounding area are all decommissioned at the end of their consented lives. If life extension and/or repowering are the norm then it would be unreasonable to assume that this would be the case.
The responsibility of assessing future cumulative impacts resulting from the repowering of a nearby scheme will rest with the developer of that scheme. Decision makers considering the first repowering application would need to take care to consistently apply the assumption of decommissioning at the end of the time limited consents for cumulative wind farms and to consider in detail the future evolution of development.
Comparative Assessment
The draft guidance recommends also submitting comparative visualisations showing existing and proposed turbines and that the scope and format of assessments are agreed through the Scoping process. SNH stresses that the existence of an operational wind farm should be given substantial weight in decision making. It will be key that decision makers view the LVIA findings in the context of a landscape whose character has included the existing wind farm for a substantial length of time.
Ecology and Ornithology
The proposed fundamental baseline assessment approach is a reasonable EIA start point in relation to ornithological and ecological assessment too. However, the draft guidance suggests that no additional ornithological surveys should be carried out to assess the impacts of repowering. Conversely, it advocates new and updated surveys for non-avian ecology.
Establishing the ornithological baseline (following assumed decommissioning of the operational scheme) would be more difficult without gaining an understanding of current bird activity as there is likely to be a lack of original data/assessment and the presence and behaviour of birds in and around the wind farm is likely to have changed substantially since the original assessment. Existing operational turbines will have altered behaviour, including flight paths, roosting and nesting and birds will have habituated over the life of the operational wind farm, to different degrees depending on the species.
SNH considers that the current presence and behaviour of birds within the study area does not need to be understood to establish the baseline or assess the future likely effects. However, surveys of current behaviour would likely be of value for a number of reasons:
- In relation to collision risk, repowered turbine locations are likely to differ to existing turbine locations due to spacing requirements and constraints. Therefore, it may be valuable to understand current flightlines and have more insight into avoidance rates, flight heights and behaviour such as flight displays in order to inform the assessment.
- Where the current turbines have created a barrier effect it is logical to survey the operational scheme to better understand this; which species are being affected and how the new design might be able to reduce effects (e.g. by avoiding certain areas or adopting larger separation distances).
- There is a lack of existing data which allows accurate prediction of disturbance effects. It would be valuable to understand which species are breeding and roosting in proximity to the existing operational turbines and also where they are located, having habituated to the operational scheme. This can then inform the assessment of impacts for the larger turbines.
The guidance suggests reasoned judgements based on available local population data, reference to the original assessment and operational monitoring data (both of which may be limited for older schemes) and any other available site survey data, such as habitat survey data. This approach would result in increased levels of uncertainty in the assessment findings and therefore greater project risks as, should operational monitoring of the repowered scheme identify larger level effects, this could lead to curtailment requirements.
The guidance notes the opportunity to assess the effectiveness of existing habitat management and enhancement (which may be limited for older wind farms). Opportunities to further improve habitats should be identified and committed to as part of the repowering EIA which is in line with the process for new wind farm development.
Other Topics
The key elements of the draft guidance are that it suggests assessments should adopt a baseline assuming decommissioning of the operational scheme and that it suggests that no ornithological surveys would be undertaken. These principles have implications for other topics. For example, it is worth considering noise modelling and assessment that will be required within repowering EIAs.
Wind turbine noise limits are set relative to background noise levels in accordance with the guidance contained in ETSU-R-97 “‘The assessment and rating of noise from wind farms’. ETSU-R-97 makes it clear that background noise levels should be measured in the absence of turbine noise. The number of operational turbines has increased enormously since ETSU-R-97 was written in 1996, which means that in many areas, particularly where wind farms have clustered together, undertaking measurements which are not influenced by wind turbine noise has become much more difficult. Good practice guidance produced by the Institute of Acoustics details a number of methods which can be used to obtain suitable background noise measurements including:
- Switching the turbines off (which is not always practical, particularly when turbines are not under the control of the applicant);
- Directionally filtering the data or subtracting predicted noise (which is not always possible depending on the spread of turbines around a location and other noise sources in the area);
- Utilising a suitable “‘proxy’ location outside of the sphere of influence of the existing turbines (if such a comparable proxy exists); or
- Utilising data collected for previous applications (if available and representative).
The approach to collecting new baseline data needs to be carefully considered on a site by site (and sometimes even a dwelling by dwelling) basis to ensure that a robust dataset is collected without placing unreasonable burdens on applicants. It will often be necessary to agree the approach with the relevant stakeholders at an early stage to avoid abortive work and expenditure.
The fact that an existing scheme has been operating without issue does not automatically mean that a repowering scheme will be acceptable in relation to noise. Many schemes that are being considered for repowering were consented before ETSU-R-97 was written and it is therefore possible that those schemes, if proposed today, would not meet the current guidance. Even more critical is the concept of limit apportionment. ETSU-R-97 provides a methodology to establish suitable limits for wind turbine noise; those limits apply to all wind turbines in an area. It is not uncommon for limits to be apportioned or shared between a number of schemes in an area and for older developments this may have been undertaken retrospectively based on the amount of the ETSU-R-97 limit that a scheme could realistically use. Consideration of the available “‘noise budget’ is another topic which should be considered with the relevant stakeholders at an early stage.
Conclusions
The SNH guidance is well timed and proactive ahead of what most expect to be an important future development for onshore wind. Notwithstanding the suggestions in the guidance, there remain a number of topic specific subtleties which will need to be carefully considered at an early stage in repowering proposals to ensure robust, proportionate assessments can be undertaken. TNEI will continue to work with stakeholders to refine and agree the scope of assessments at an early stage so that an efficient and proportionate EIA process can effectively inform decision making.
For further information on the implications of the guidance or to discuss any aspect of your wind farm development, please email Jason McGray or call 0191 211 1430.
