February 19, 2019
Scotland

Windfarm planning change leads to peat slide risk row

By Claire Smith | Ground Engineering | 19 February 2019 | www.geplus.co.uk

An application by Viking Energy to use larger turbines at its planned Viking Wind Farm project in Shetland has led to calls for further investigation of the ground condition risks to the project.

The onshore wind farm could become the UK’s third biggest if it gains planning approval, however, campaign group Sustainable Shetland believes that ground risk issues have been overlooked.

In an open letter to the Shetland Islands Council’s planning committee, Sustainable Shetland vice chair James Mackenzie has called for greater scrutiny of the risk of peat slides within the scheme site.

Mackenzie said that the details of the risk were revealed in a report by Andy Mills of AM Geomorpholgy which was appended to the planning officer’s report on the Viking Wind Farm variation application.

Mackenzie said, in his open letter: “Mills’ report concerns the issue of peat slides, which are known to occur in Shetland with increasing frequency and with potentially devastating, even life-threatening, consequences. It is of great significance that new Scottish government guidelines on peat stability assessment (PSA) issued in 2017 recognize the special characteristics of peat. Please note the following extract, the final paragraph (bolded and italicised) of which implies that the original PSA supplied by Viking Energy in its 2009 environmental impact assessment, and submitted, without amendment, for its Variation Application, is inappropriate and/or unreliable.”

Mills’ report states: “Peat landslides are a characteristic landscape response of peat uplands to intense rainfall events, and the importance of understanding their impacts and the potential for their occurrence is now well understood. It is estimated that Scotland’s peatlands hold approximately 50% of the UK’s total soil carbon store (Cummins et al., 2011), and as infrastructure pressure on peat uplands increases, the potential impacts of wind farm developments must be considered alongside their potential benefits.

“In recent years, costs and benefits have been considered not just in terms of the stability of the peatland (this guidance), but the volumes of peat excavated, reused and potentially lost during construction (Scottish Renewables and SEPA, 2012) and the carbon balance of the wind farm (Scottish Government, 2011). In recognition of the importance of peat as a carbon store, a number of policy documents and national plans make clear the Scottish Government’s intention to protect, manage and restore degraded peatlands to their natural functions, biodiversity and benefits, and in so doing create a source of carbon sequestration (Scottish Government, 2017; Scottish Natural Heritage, 2015a).

“Just as wind farms and their associated infrastructure may be affected by or cause peat landslides, other infrastructure such as road networks, flood defences, drainage, power lines, residential areas and farmland may also be affected. Terrestrial habitats in the path of a peat landslide may be damaged by ground displacement and by burial by debris, and aquatic habitats damaged by incorporation of landslide debris in watercourses (McCahon et al., 1987). In addition, the displacement and break-up of peaty debris after a landslide event will ultimately result in small scale depletion of the terrestrial carbon store (Nayak et al., 2008).

”Typically, slope instability and landslide hazard assessments have followed a standard approach, detailed in a number of statutory and guidance documents (e.g. BS5930, 1999; Department of Environment, 1990; 1996). However, previous investigations have illustrated that the geotechnical controls of peat landslides differ from landslides in mineral soils (dry peat is typically 90% – 95% organic matter) and that pre-conditions for failure are not well accounted for by site investigation methods detailed in existing documentation. For example, peat has special hydrological properties (90% water content), it has a very low density and is often very fibrous in nature (Hobbs, 1986, 1987). Therefore, this guidance has been developed to ensure that appropriate and reliable peat landslide hazard and risk assessments can be undertaken during the planning of upland electricity generation developments such as wind farms…”

Mackenzie has called on the planning committee to reject the planning variation “or at the very least I would hope that a condition requiring resubmission of the PSA is attached to any approval”.

Mackenzie added: “That the draft conditions do not include any consideration of peat stability is a major omission.”

GE understands that the application to increase the tip height of the turbines will raise the permitted maximum height from 145m to 155m to allow the project to benefit from the latest turbine innovation, which ahs moved on since outline permission was granted in 2012.