Peat assessments and wind farms

3rd May 2013

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Conrad Trevelyan examines the interactions between environmental impact assessment (EIA) specialisms during peat assessment for wind farm proposals

In a previous IEMA EIA Quality Mark article, Julia Tindale of RPS Group discussed the Joint Nature Conservation Committee and other statutory consultees’ currently emerging guidance on the assessment of peat resources, with particular regard to wind farm development.

The article identified the key features of the guidance, such as the need to avoid peat deposits where possible; to reduce impacts; and to quantify any potential impact on the peat resource and mitigate where appropriate.

The article touched upon the multidisciplinary nature of some features of the required assessment and this article attempts to expand upon this aspect of peat impact assessment for wind farm proposals.

Owing to the relatively recent nature of peat assessment guidance and the involvement of multiple consultee interests, it is important to comprehensively scope the nature of the assessment work required before commencing. Regular briefings on the progress of the work will often help to maintain consultee confidence in the adequacy and appropriateness of the assessment.

Interaction between EIA specialisms is reasonably commonplace. For instance, close cross-working between ecologists and hydrologists is a prerequisite of a successful assessment during wind farm design in an upland environment where changes to either watercourse or surface water characteristics may have profound and lasting changes on flora and fauna, through changes to water flow quality or quantity. Correspondingly, notable changes to ecological habitats such as the felling of forestry trees may have impacts upon the rainfall run-off into local watercourses.

Recent experience has shown that the assessment of peat resource is a particularly multidisciplinary process due to the various characteristics and features that need to be understood.

First, peat-based habitats such as bog pools need to be surveyed and their relative rarity and sensitivity understood.

Second, the importance of the peat bodies in maintaining water quality (or indeed the potential for polluting watercourses if incorrectly handled) should be assessed.

Third, peat slide risk must be determined and mapped. And, lastly, the carbon storage and sequestration properties of the peat and peat habitats must be quantified to satisfy consultee guidance requirements.

Initially, baseline work from each specialism may be best gathered independently to understand the large scale sensitivities that will drive the design of site layout, in effect drawing upon the independent surveys required from each topic area, irrespective of the peat resource. This data may then be synthesised with desktop assessment of the peat resource drawing on sources of high level soil surveys, aerial photography and the like, and used to inform the site layout such that the most sensitive areas of peat are avoided.

However, once preferred areas for turbine and track location are defined, optimisation of survey effort may be achieved by conducting peat-focused site work in multi-disciplinary teams of ecologists, hydrologists and civil engineers to map and quantify the resource which may be impacted upon in respect of each specialism.

This peat-specific site survey work is likely to require:

  • peat probing at each proposed turbine base and track line;
  • peat sampling via coring and laboratory analysis;
  • measurement of peat shear strength with hand vanes;
  • observations on peat habitat and quality, and
  • observations or recording of the water tables present during survey or over a period of time.

Agreement should be reached with consultees on the sampling resolutions for probing and other measurement activities. Dependent on the potential development area, a site-wide survey at the level of detail described above may well be an impractical (and unnecessary) proposition and this should also be discussed with the relevant consultees. With this in mind, it is also important to be able to present evidence as the design progresses that areas of greatest sensitivity have been avoided during the early desktop stage wherever possible.

The more detailed, peat-focused site survey work may then be used primarily to microsite turbines and tracks, and to quantify the final impact of the proposal.

The requirement to discuss different elements of assessment with different consultees, for example within a Scottish context Sepa (Scottish Environment Protection Agency) for carbon analysis and waste management of peat and Scottish National Heritage for the protection of sensitive habitats, potentially complicates matters and there is a need to agree the nature of the potentially significant sensitivities with consultees to focus survey effort appropriately.

In Wales a single body, Natural Resources Wales, drawn from and replacing the roles played by Countryside Council for Wales, Environment Agency Wales and Forestry Commission Wales, is in place as of April 2013 and should be well placed to deal effectively with such topics and issues. It remains to be seen how this body develops in this respect and more generally, and whether this model will be followed elsewhere within the UK.

This article was written as a contribution to the EIA Quality Mark’s commitment to improving EIA practice.

Conrad Trevelyan is senior project manager, wind development services, at Dulas


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