LONDON — A proposed onshore wind farm development in Sutherland, Scotland has been substantially reduced in size following an environmental impact consultation.
Developer SSE’s proposal for its Strathy South wind farm, which has been in the planning stage since 2007, has been reduced from 77 turbines to 47. In addition, the number of access tracks has been reduced; the grid route has been moved; the distance from the turbines, access tracks and surrounding development to designated areas and watercourses has been lengthened, and a bird corridor has been introduced. SSE said it had “undertaken a considerable amount of further work and consultation to address the feedback from consultees and improve the design.”
At issue were potential impacts on surrounding peatland, the landscape and wildlife, notably local bird species.
Health, safety and sustainability consultancy Environ worked with SSE to make the changes. Matt Davies, head of Environ’s environmental planning practice, said multiple potential environmental impacts were taken into account. “One risk was with birds that breed and feed on the ground-based habitat, which might be lost or disturbed by the physical presence of infrastructure and access tracks. The other principal impact was associated with the risk that birds, particularly raptors, will collide with the turbine blades.” Potential disturbance of peat land, which emits stored CO2, was also considered, he said.
The Scottish government will now hold a formal consultation on the revised plans. The wind farm site lies several km south of another SSE project, Strathy North, which will contain 33 turbines and is scheduled to begin main construction later this year.
Davies said the reduction in the wind farm’s proposed size is unlikely to affect SSE’s business case for the development. “This doesn’t affect it materially,” he said. “Without having had discussion with our client on this matter, I can’t imagine that any developer would progress an application that was uneconomic. The scale has been reduced and this will probably mean the number of megawatts will have been reduced from what was anticipated,” he said. SSE has not confirmed what Strathy South’s new capacity will be, but a spokesperson said that while the old plan specified 77 2.3 MW turbines, the new plan’s 47 turbines “can be up to 3.4 MW”, for a total capacity of up to 139.8 MW or a reduction of around 37 MW.
SSE also said the turbine tip height in the new plan has been increased from 110 to 135 metres.
Regarding the wind project’s potential impact on local bird species, Davies pointed to early-stage work by scientists that suggests that certain bird species tend to habituate more readily than was previously thought to construction noise and disturbance. To calculate potential bird impacts, Environ uses the widely-accepted Band model to describe the potential for bird-turbine collisions, and additional results from Scottish National Heritage’s seven-year empirical bird monitoring study.
Recently published information has slightly refined how the Band model is used in relation to bird and wildfowl species, Davies said. The model relies on a concept known as the avoidance rate, a percentage which represents the number of bird species flying toward the face of a wind turbine that will take evasive action. Typical avoidance factors are around the 98 or 99 percent mark, Davies said, and Scottish National Heritage (SNH) has recently published new research that suggests a slightly higher degree of avoidance for certain species, such as the Scottish white-fronted goose. The figure previously stood at 99 percent and has been revised by SNH to 99.8 percent.
It is not uncommon that developers amend applications as circumstances change or additional environmental impact information is collected, said Davies. “If the impacts are shown to be potentially significant,” he said, “reducing the size and scale of development to mitigate any significant effects is something developers take seriously.” Size and scale reductions through a process of assessment, investigation and analysis are common, he explained.
The typical time from initial conceptual design and discussion with stakeholders to determine the appropriate scope of an impact assessment to an application supported by an environmental statement is normally two to three years, Davies said. Once the application is submitted, the process of determination leading to planning permission can take one to two years.