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Environmental Impact

Introduction   Assessment   References  


To date no full scale Marine Current Turbine (hereafter referred to as MCTs) development has been installed - only small short-duration trials have made it into the water. As a result no environmental impact has been carried out. Our development, if given the go ahead would require an EIA to be completed and therefore we looked at the impact of MCTs on the following areas:
  1. Visual Disturbance
  2. Environment
  3. Ecology
  4. Construction
  5. Geology
  6. Others
Any impact from an underwater development would fall into one of two categories:
  • Effects common to construction projects such as noise & visual impact, disturbances during installation and access for construction and maintenance.

  • Effect that are unique to a tidal scheme such as the interaction between the blades and marine animals and the influence of tidal energy extraction on other costal processes.
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  1. Geographical Description of Areas

  2. This environmental assessment would require undertaken for the proposed developments of MCTs in the following areas:
    • Mull of Kintyre
    • Islay
    • South Ronaldsay
    • Dorus Mor / Dorus Ledges
    • Kyle of Rhea
    To the best of our knowledge, each of the sites selected are in relatively remote coastal areas around the coast of Scotland (with the exception of Kyle of Rhea) with little or no human interaction. All of the locations are out with Sites of Specific Scientific Interest (SSSI).

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  3. Economic Description of the Areas

  4. This includes fishing activities, ports, shipping, dumping, MOD and recreational activities.

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  1. Visual Disturbance

  2. As the development will be mostly underwater, visual impact is expected to be minimal during routine operation - only the relatively short cylindrical towers of the MCT devices will be visible. It is expected that when the sites are operational, power transmission lines located on the foreshore will be visible and these installations will undergo a routine land based planning application procedure. All steps will be taken to integrate the transmission system into the natural environment.

    During construction the visual impact on the surrounding areas will be high due to the physical work required to install the turbines. This will however be removed upon completion, returning the site close to its natural state.

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  3. Environment

  4. Environmental considerations play an important part in the location, design, construction, operation and public acceptability of all major energy developments. At the present time, since MCTs are still a relatively new technology there are no comparable facilities in place to use as a reference.

    However, since the locations we have selected experience high tidal velocity the seabed tends to be scoured, leaving very little organic matter. Thus habitat loss and risk to species of conservation would be deemed to be low as many sources state that sites such as the proposed locations are relatively “species poor”. However, it should be noted that Scottish Natural Heritage believe that there may be specific flora and fauna in these sites (in small quantities) that cannot be found elsewhere. This area requires extensive research to evaluate the specific impact of development on each site.

    MCTs have the environmental benefit that they emit no greenhouse gas emissions or pollutants during routine operation. Marine pollution would be restricted to matters related to leakage of lubricants and the type of paint or coating that the subsurface structures would use to prevent excessive growth of marine organisms, some of which can be extremely toxic (however, those used in the MCT design are non TBT, so should not be poisonous). Any materials used during construction and operation of the turbine would need to be carefully selected with any implications fully considered. There may be some issues related to the construction of the MCTs such as energy use and heavy metals.

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    1. Global Issues

    2. Electricity generation using tidal currents would use a very small fraction of the overall energy input to the oceans from the gravitational interplay between the Earth and the Moon. Considering the scale of the schemes proposed in global tidal energy terms, the amount of energy being extracted by an MCT farm would likely have a tiny effect on the macro tidal energy balance. As stated above MCTs do not produce any discharges or emissions and would therefore make almost zero contribution to the problems of air pollution or global climate change (only construction to factor in).

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    3. Regional Effects

    4. It is predicted that there is unlikely to be any meaningful change in tidal height or timing due to the installation of MCTs. However, immediately downstream form the units there may be a decrease of about 10% in the current velocity. It is uncertain what biological effects may result from this change. At first sight, it would seem reasonable that changes, of the magnitude suggested, would be unlikely to affect physical processes such as sediment suspension and deposition. On the one hand, it may be argued that tidal currents are naturally and continually changing and that the change predicted here falls within that range of normal variation. If this were so then we would not expect to see any adverse effects. On the other hand, effects on biological processes may be subtle and telling on some species.

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  5. Ecology

  6. The issue of the effect of MCTs on fish and marine mammals is a major environmental concern and as previously noted very little information exists on the subject. The MCT blades rotate much slower in relation to hydroelectric and wind turbines, in the order of a small number of revolutions per minute depending on the equipment size and tidal current. As a result it is considered unlikely by the manufacturers that marine life will be affected by the gently rotation of the blades.

    If upon installation this transpires not to be the case then it could be possible to retrofit the MCTs with a screen to keep fish from entering blade area (though this may impact performance). In addition other behavioral means of keeping fish and mammals away e.g. tickle voltages and strobe lights could also be used [1].

    It has been stated that the low frequency sub-sea noise that would be emitted during operation would not interfere with the echolocation capability of cetaceans and also serve to warn marine mammals to keep away.

    Public concern may arise over the rotor of a MCT potentially hitting fish or mammals. However this is unlikely because small and medium sized creatures would tend to be pushed out of the way by the blades (due to fluid dynamics) and larger mammals, such as seals, whales and dolphins, are known to avoid ships and ships propellers and could be expected to exhibit that same behaviour with MCTs. Also, a ship's propeller, which is accepted without question for widespread use at sea, is a far greater hazard as it rotates at far greater speeds, e.g. up to 10 times faster, and it is attached to a moving vessel that may travel faster than the fauna.

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  7. Construction

  8. During construction there will be considerable movement of vessels between nearby ports and the MCT locations. In the worst-case situation, the construction vessel movements are additional to existing movements, with no accompanying diminution of existing commercial or recreational navigation traffic in the area. Even in such a situation there may only be a small increase in the risk of collision in the vicinity of the main routes used to service the farm. Similarly, the risk of having to deviate from well-established routes to avoid construction traffic/activities may be small. Such deviation can have cost implications to shipping companies and fishermen as well as representing a ‘nuisance’ to sea users. It is expected that this will not be a major issue as the sites chosen for the MCT farms are relatively remote - however, there will doubtless be some impact.

    Each MCT will require construction work in and around the seabed to keep the turbine in place and to secure the electrical transmission cables. This would result in temporary impacts associated with excavation, including possibly blasting, material deposition, and grouting. Species at risk would be those least likely to be able to move out of the way quickly such as some benthic fauna and flora. In the case of blasting, fish near the blast zone would be vulnerable to the effects of the blast shock waves. It would be necessary to assess these effects and where possible select areas where impacts may be avoided and, in others, establish procedures whereby the adverse effects of these activities may be minimized. With prudent planning and execution these impacts would be temporary in nature.

    The timing of work needs to be considered in light of seasonal migrations of sea animals. Oil and fuel storage and use on barges, in inter tidal zones and at port facilities will need to be well managed. Standard practices, already developed and in use in the maritime industry should be effective.

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  9. Geology

  10. Installation of the individual MCTs and transmission cables may cause sediment displacement, which in turn could cause dangerous particles already lying in the seabed to be dispersed and contaminate the local environment e.g. radioactive particles. The proposed sites will have to be analysed for contaminants.

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  11. Others

    1. Military Exercise Areas

    2. The MoD assesses proposals for offshore developments on a case-by-case basis as part of the planning process. Each of the MCT farm sites has been chosen to avoif areas of military usage wherever possible, though these sites may be used by the MOD at times for through-routes. More detailed investigation will be required to assess if such developments would cause a problem to the MOD.

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    3. Commercial & Recreational Shipping

    4. The presence of a tidal current power plant in narrow and well-used waterways would be a concern for all marine traffic. This includes barges, cruise liners and recreational and commercial fishing boats. If the entire structure could be a distance below the water line so that the water column that would not interfere with the largest vessels using these water ways, the impact on shipping could be substantially reduced. For configurations where support structures are above the ocean surface (such as that of the MCT design), it would be necessary to deny access to all vessels over the full area of the power farm. Given that ships/boats do from time to time lose power and are vulnerable to storm conditions, which blow them off course, the fully submerged option clearly has some advantages. Both commercial and recreational fishing would probably be impossible over the area of the power farm. It is likely that an "exclusion zone" would have to be designated where the site was installed.

      Each of the sites have been chosen to minimise contact with commercial shipping routes. As a result it is expected that the developments proposed as part of this project will have only a small impact on shipping. Each of the MCTs will have an Automotive Identification Systems (AIS) installed on board to alert shipping to their presence.

      Current Government policy is to encourage active participation in recreation and sport including yacht cruising and racing, power boating, dingy racing, windsurfing and power boat racing. Trends in boat ownership show that the size and mast height of privately owned yachts is increasing. In addition, demands for boating facilities continue to outstrip supply indicating a growing recreational sector. At present the proposed areas for the farms are often used by small yachts and pleasure craft, so there would be an impact in this case, especially if the installations are to be large in area, as in the maximum storage scenario.

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  1. Triton Consultants Ltd (2002), Green Energy Study for British Columbia Phase 2: Mainland, Vancouver BC, Triton Consultants Ltd.

  2. Binnie, Black & Veatch in association with IT Power(2001), The commercial prospects for tidal stream power, ETSU T/06/00209/REP, HMSO.

  3. Scottish Hydraulics Study Group (March 2004), Proceedings from the Sixteenth Annual Seminar on Hydraulic Aspects of Renewable Energy, Institution of Civil Engineers.
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