Guernsey Regional Environmental Assessment of Marine Energy


Title: Guernsey Regional Environmental Assessment of Marine Energy
Publication Date:
July 01, 2011
Pages: 59
Technology Type:

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Website: External Link
Attachment: Access File
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Guernsey Renewable Energy Team (2011). Guernsey Regional Environmental Assessment of Marine Energy. Report by Guernsey Renewable Energy Commission. pp 59.

The full report is available at the bottom of this page.


Background to the REA The Bailiwick of Guernsey is situated in the English Channel, thirty miles west of France’s Normandy coast, and is well positioned to harness the power of the sea. Potential exists to generate both tidal and wave energy; the area has some of the strongest tidal currents in the world and receives powerful waves from the Atlantic Ocean.


The States of Guernsey’s Energy Policy Report, published in June 2008, recommended the formation of the Guernsey Renewable Energy Commission (GREC) to progress the creation of local renewable electricity generation on a large (macro) scale. The Energy Policy Report of June 2008 recommended that the States should investigate targets to reduce the emissions of carbon dioxide by 30% on 1990 levels by 2020, and by 80% by 2050, and to generate 20% of electricity from local renewable sources by 2020.


GREC has undertaken investigations into the feasibility and promotion of marine renewable energy developments within the Territorial Waters (within three Nautical Miles) of the islands of Guernsey, Herm and Sark. A key aspect of GREC’s work has been producing a Regional Environmental Assessment (REA) which examines the likely environmental effects from the development of wave and tidal power production.


The REA is a strategic study that will underpin the development of marine environmental planning policy and will inform subsequent project specific Environmental Impact Assessments to be undertaken by individual energy developers. The results will be used to prepare and deliver the States of Guernsey’s strategy for the development of marine energy generation facilities and associated infrastructure in Guernsey’s waters.


Purpose In the UK, it is a legal requirement to produce a Strategic Environmental Assessment (SEA) for all spatial plans and development programmes. However, there is not presently a legislative requirement to perform a SEA as Guernsey falls outside the scope of both UK and EU laws. Although the document will be referred to as a Regional Environmental Assessment (see below), GREC has decided to adopt the general principles of the SEA framework in order to demonstrate transparency and to facilitate ease of understanding for potential developers.


The purpose of the REA is not simply to inform policy makers and the public of the possible environmental impacts of pursuing such targets. The important value of the REA is in its use as a tool to manage environmental risk. As a result, not only can appropriate mitigation measures be applied, but also Guernsey and Sark can properly benefit from reductions in greenhouse gas emissions and the security of supply that would be afforded by marine renewable energy.


The REA has been undertaken to provide a strategic assessment of the potential effects that marine renewable energy devices (wave and tidal) will have on the environment of Guernsey, Herm and Sark.


The REA aims to identify, evaluate and describe the likely significant effects, both positive and negative, of developing marine renewable energy. In keeping with UK best practice, the Precautionary Principle has been used throughout the assessment. This means that where there is uncertainty relating to potential effects, or a lack of information on which to make accurate predictions, then the assessment has assumed a ‘worst case’ scenario.


Scope The REA has taken account of shoreline wave, near-shore, tidal stream and potential combinations of the devices. The REA has also considered the impacts of infrastructure that is necessary to connect devices to shore, including electrical cables and shore-based control equipment. It was decided to exclude both tidal range and offshore wind devices from this initial report.


In doing this the REA considered in detail the following areas:


  • Physical Marine Environment
    • Geology
    • Marine Processes
    • Water Quality
  • Marine Biological Environment
    • Benthic Ecology
    • Pelagic Ecology
    • Birds
    • Marine Mammals
  • Marine Human Environment
    • Commercial Fisheries and Mariculture
    • Recreational Fishing
    • Marine Coastal Historic Environment
    • Existing Submarine Cables, Electrical Grid and Connectivity
    • Shipping and Navigation
    • Tourism and Recreation
  • Other Topics
    • Noise
    • Air Quality
    • Landscape and Seascape Character


Objectives As described in the Scoping Document of October 2009, the main objectives of the REA are:


  • To assess, at a strategic level, the potential effects of marine renewable energy devices on the environment
  • To advise and support the States of Guernsey in the development and implementation of its strategy for marine renewable energy
  • To inform the future development of planning guidance for marine developers
  • To provide information for use in the development of a separate Marine Spatial Plan for Guernsey
  • To form a vehicle for public and stakeholder engagement


Outputs Based on the above objectives, the main outputs of the REA process are:


  • A record of the baseline situation, based on available information
  • Identification of gaps and inconsistencies in the baseline data and the need for further survey work, studies and ongoing monitoring
  • Commencement of ongoing consultation
  • Assessment of the generic effects of marine renewable devices on the marine environment
  • Recommendation of generic mitigation measures to avoid, reduce or offset any significant adverse effects on the environment


Project Overview Initial studies into the waters surrounding the Channel Islands, such as the Tidal Stream Resource Assessment prepared by Robert Gordon University, demonstrate that there is a potentially valuable resource in the waters around Guernsey, Herm and Sark.


In collaboration with the government of Sark, and with technical specialists from Guernsey and the UK, who have formed the Guernsey Renewable Energy Forum (GREF), GREC has now completed the REA. This REA has been prepared for the purpose of consultation with the public, technical specialists and stakeholders.


To help meet Guernsey’s renewable energy targets, the focus of the REA has been on the development of large commercial sites. GREC is not looking for companies to test or develop designs for wave or tidal devices in its waters. It plans to only accept proposals from developers with a pre-tested, working device, with arrays that would contribute electricity to the Guernsey grid or to overseas markets.


The area of study for this REA covers the territorial waters (within three nautical miles of the shore) around Guernsey, and Sark. The other boundaries to the study are the oceanographic parameters under which current tidal and wave technologies are intended (and able) to operate in.


GREC has met with developers of marine renewable energy devices to learn about the operating characteristics of the devices and their potential environmental effects. Developers have also been invited to join GREF in order to continue to offer their advice.


A small number of development scenarios have been devised. These scenarios reflect the potential size of the marine energy resources that exist within the waters around Guernsey, as well as Guernsey’s targets for renewable energy. A feasibility study has been produced in support of the REA to act as a technical reference for environmental specialists in the delivery of their analyses.


  • Maximum development scenario (230MW) - This would utilise the resources to a maximum potential, and could include several large (>40MW) arrays. These could be located at sites that benefit from high velocity tidal flows such as the Big Russel, to the north of Guernsey and to the south-east of Sark, together with wave energy arrays to the north-west of Guernsey
  • Minimum development scenario (100MW) - This allows for the minimum deployment that would meet Guernsey’s renewable energy targets in the medium term future, and would require two 50MW tidal arrays.


The development scenarios did not specify actual development sites, as it was considered that to do this would have pre-judged the results of the REA, and prevented the authors from giving consideration to the sensitivities that exist throughout the whole of the study area. Site selection or ‘Zoning’ will be undertaken on completion of further strategic investigations and consideration of policy.


Different device technologies require different footprint areas and space between devices for deployment and safe effective operation. However, to allow the visualisation of the likely footprint of the arrays that could be deployed, the following was used:


Example tidal array:


A 50MW array, comprising up to 50 individual devices, would be expected to occupy approximately 0.5km2 of the sea-bed. The array would probably be arranged as two to four rows of devices, aligned at 90 degrees to the primary flow direction.


Example offshore wave array:


A 20MW array deployment area, comprising up to 50 individual point absorber (buoy) devices, or a smaller number of larger devices, would be expected to occupy approximately 8.0km2 of the surface of the sea, including the space between the devices. This array would probably be arranged as a 2 x 4 km rectangle, aligned so that the longest edge of the deployment area would face the primary wave direction.


Summary of Key Findings


Data Gaps


The assessment has found a number of areas of investigation that are hampered by a lack of knowledge. As the REA is a desk-study, it is acknowledged that some of these cannot be addressed within the scope of the study. Further investigative work has been recommended for future stages of the environmental planning process. The main reasons for data gaps are:


  1. Lack of baseline information.
  2. Lack of information with regard to likely deployment sites.
  3. Lack of information regarding device characteristics.
  4. Lack of information regarding the devices’ response to potential impacts.


The data gaps that have been identified on an area by area basis are identified as future studies and surveys are incorporated into an Environmental Action Plan (EAP) and a Regional Monitoring Plan (RMP) in Appendix K and L respectively.




The following locations were highlighted as being of significance with regards to the specific areas noted.


Bird breeding – Cliff areas are identified on all of the islands as actual and potential breeding sites.


Grid connections – Telecommunication cables are shown connecting Guernsey to the UK and France. There is also a power cable on the east coast of Guernsey, which connects to France via Jersey.


Tourism / Landscape – Areas of coast on all of the islands are identified as having important landscape value.


Commercial fishing – The most important areas for commercial fishing are focused over sand banks. The Boue Blondel to the west of Guernsey is an important fish spawning ground. The Great Bank off the east coast of Guernsey is extensively fished, as are the sandbanks to the south and north of Sark.


Geology – In the context of sediment dynamics, the critical areas of the Guernsey REA include the channels of the Big and Little Russels, where there is the highest potential for tidal generation. Although there is a general understanding of the sea bed geology and sediment distribution in these areas, the specific relationships between this and the deployment of energy devices on sedimentation is not yet established.


Marine mammals – There is a dolphin feeding ground off the southern tip of the Great Bank, which mostly comprises mackerel. There is also a seal haul-out site at the Humps, north of Herm, which supports a resident population of seals. There are believed to be resident populations of common dolphins off the north of Sark and the north and east coasts of Guernsey.


Marine and coastal historic environment – The areas identified as being of greatest importance are: the area surrounding Vazon Bay on the west of Guernsey; outside Guernsey Harbour; between Herm and Jethou; and to the north of Herm. These areas have been identified as having a high concentration of wrecks.


Navigation – The area through the Little Russel is the key shipping channel into and out of Guernsey. Less sea traffic uses the Big Russel, although it is still an important route.


Recreational fishing – Key sites are the Great Bank to the east of Guernsey and the north coasts of Herm and Sark.


There were no clear thresholds that emerged from the assessment. However, the analysis of several of the disciplines was hampered by a lack of baseline information, as well as a lack of prior industry experience of multi-device arrays. Therefore, the REA has concluded that the cumulative effects of multiple devices, or multiple arrays, are unknown at present.


Mitigation The primary mitigation measure would be the careful selection of deployment areas to reduce the visual impact as much as possible. This should be followed by careful design of devices to minimise visual impact. It is clear that some devices are more visible than others, and this may preclude the selection of certain types. On completion of site selections and initial enquiries from developers, detailed visual assessments of specific device proposals should be undertaken to inform project specific requirements. Developers should be encouraged to optimise their designs to minimise visual impact.


Monitoring and Action Plans The production of the REA has included the preparation of two key documents: the Regional Monitoring Plan (RMP) and the Environmental Action Plan (EAP). These may be used to manage the delivery of future investigations and the delivery of project-level mitigation measures. The documents identify the environmental survey work, studies and practical measures that should be undertaken through the development of actual projects, from their inception to decommissioning.


The RMP and EAP identify the organisations most likely to be responsible for the implementation of each of the actions. However, it is acknowledged that effective delivery of environmental mitigation can only be achieved through close collaboration between all parties involved. With this in mind, it is likely that tasks will be shared, by agreement, among the States of Guernsey, Sark and prospective developers.


The Regional Monitoring Plan The RMP lists scientific investigative work to be undertaken throughout the development of marine renewable energy facilities. This includes strategic-level investigations from project conception, which cover the whole study area, to project specific post-construction monitoring work, which will confirm the performance of individual arrays of generators and the effectiveness of mitigation measures undertaken.


The Environmental Action Plan (EAP) The EAP lists physical measures that could be taken to protect the environment during the design, deployment, operation and eventual decommissioning of generator arrays, depending on the nature and location of development.


Conclusions The REA concludes that, if appropriate mitigation measures are taken, the establishment of a generating capacity of 100MW can be achieved with generally minor effects on the environment. However, there are notable gaps in the knowledge that has been available to the study. Informing strategic planning and project-level decision-making are the key objectives of the REA. The following key issues require consideration.


  • There is a need to obtain better information with regard to:
    • Existing benthic-habitat mapping
    • The behaviour of large fish and mammals in response to the presence of devices
    • The feeding behaviour of seabirds
  • The severity of potential impacts has been found to be highly dependent on location. The progression of detailed development proposals requires the careful selection of preferred renewable energy deployment zones. The nature and severity of potential impacts is highly dependent on the mode of operation and the characteristics of the devices to be deployed.


Next Steps The REA should be considered as a working document. It may be reviewed and updated as necessary to account for additional survey information or the completion of research. As new technologies are developed, they may be assessed and incorporated into future versions of the REA.


The timescale for the deployment of marine renewable energy devices in Guernsey’s waters is difficult to determine. It is clear that an exploitable energy resource exists, particularly with respect to tidal energy. However, the time the industry requires to develop devices to the point that they can be manufactured and deployed at commercial scales is unknown. Furthermore, the cost of renewable energy is still high in relation to that produced from fossil fuels, and this may deter early adoption. Discussions with a number of developers indicate that they anticipate readiness for deployment (machines in the water generating electricity) on a commercial scale by 2015 at the earliest.

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