Dorset Wildlife Trust
Position Statement
Title Navitus Bay offshore wind park
1. Scope
The scope of this position statement in relation to the proposed Navitus Bay development is restricted to wildlife and environmental impacts. It does not cover for example landscape value perceptions, economic growth, employment opportunities, viability, feasibility, or aesthetics. This document lays out DWT’s view and position on a range of natural environment related issues.
2. DWT position
a. DWT can only comment on the wildlife and natural environment implications of this development. Our aim at this stage, with the information available, is to clearly state our expectations rather than to pass judgement as to whether the development should progress.
b. Dorset Wildlife Trust is in principle supportive of renewable energy production because it is important to significantly reduce carbon emissions to prevent the worst effects of anthropogenic climate change and ocean acidification.
c. Our default position will then begin with support for such projects, providing negative impacts on the natural environment are fully assessed, and shown to be minimal. Adequate avoidance, mitigation and compensation must have taken place and the development needs to provide an appropriate net biodiversity gain.
d. Several potential benefits for wildlife from the proposed development are possible, if it goes ahead, such as habitat for encrusting and hard substrate marine species as well as physical protection from capture for mobile species attracted to the turbine bases. There is also scope for restoration of terrestrial habitats such as heathland and linking of key wildlife sites along and around the pipeline routes.
e. The provision of hard marine habitat, different from that currently present, is likely to increase biodiversity, but that is not necessarily advantageous if the background habitat is artificially altered.
f. There are however concerns regarding negative impacts, including the effect of rotor strikes on sensitive or rare local populations of migratory birds (such as nightjar and hobby) and seabirds (such as gannets), and also heathland damaged by the onshore pipeline development.
g. If the development proceeds, DWT urges Navitus Bay Development Ltd to commission independent surveys during the development and operational phases to ensure sensitive local bird populations and heathland are not being harmed.
h. The lethal and sub-lethal effects of high energy noise on cetaceans and fish during construction of the footings is also a concern.
i. If the development is approved, the standard protocol for dealing with negative impacts must be employed, i.e. in order of decreasing preference: avoid, reduce, restore, offset.
j. There must be a net gain for the environment on which this development is dependant. A small but significant percentage of operating profit reserved for community support should be put back into the environment managed by independent bodies such as the government established Local Nature Partnerships.
3. Background
There is a proposal currently out to consultation for the development of a large wind park sited in offshore Poole Bay 14km SW of Durlston Head. As of the date of publication of this position paper, the wind park will consist of a maximum of 194, 177m high or 121 200m high (base of column to tip of rotor) turbines over an area of 153 km2 (59 sq miles). The turbines will each produce 5 – 8 MW totalling up to 1.1 GW generating 3.3 TWh per year. This is the expected output based on 35% of installed capacity. Numbers of turbines, production capacity and dimensions are though changing with technological advances and available finance. The turbines will be held in place with either mono-piles, a rock covered gravity base, or several piles.
Additionally a network of cables will connect the turbines with a cable to shore near Barton-on-Sea linking a 35 km on-shore, underground cable route to a national grid connection point at Mannington sub-station, West Moors.
The cable export corridor runs through sandy habitat in Christchurch Bay, one branch crossing the tip of Christchurch Ledge and one cutting through Dolphin Sand/Dolphin Bank. The corridor continues across mostly coarse sediment to meet the turbine array area.
The seabed in the turbine array area is characterised by exposed rock (described as high energy circa-littoral rock) or coarse, consolidated sediment, with encrusting fauna such as sponges, ascidians, soft corals, hydroids and bryozoans. In places, this is overlain by a thin veneer of mobile sediment. The offshore section of the turbine array area contains chalk bedrock, chalk cobbles. Small patches of piddock-bored clay were found in limited locations. The development site sits between the Studland to Portland Reefs Special Area of Conservation (SAC – a European designation) and the Wight-Barfleur reefs SAC.
On land the cable passes through several areas of protection. In Dorset, these include internationally important heathlands and the River Avon designated as Special Protection Areas (SPA), Ramsar Sites and Special Areas of Conservations. There are also nationally designated habitats such as the Moors River and many Sites of Nature Conservation Interest (SNCI) designated at a county level, mainly for
heathland and grassland habitats. These habitats support a range of rare and protected species such as nightjar, Dartford warbler, sand lizard and smooth snake.
No port has yet been chosen for the construction facility though Poole and Portland have been mentioned as possible bases.
A decision is expected from the Secretary of State for Energy & Climate Change in 2015. The timing of the start of construction would depend on the consent, but then last 4.5 years. The wind park is expected to be decommissioned by total removal at the end of the operational phase.
4. Phases of development
There are at least 4 main phases of the wind park that have implications for the natural environment:
Surveying. One of two major concerns within this phase is related to the lethal and sub-lethal effects of seismic testing on fish and cetaceans if this was actually conducted. Large mobile species, if given warning in the form of lower intensity sound, can avoid the area, but some species such as seahorses in Studland Bay and nesting fish may be unable to avoid the damaging levels of sound. Damaging impacts on cetaceans and protected species need to avoided, and minimised on other species. See references for a code of practice on the use of acoustic surveys such as multi-beam expected to be far less damaging.
The second concern relates to test drilling or pile driving. Impacts from the vibrations of both activities need to be minimised as per seismic surveying. No cutting muds should be discharged and should be water-based. Suspended solids transported away from the site should be minimised.
Construction. DWT would expect the impacts of piling or drilling, as described in Surveying above, to be minimised. A supply base may need to be constructed noting that Poole Harbour is covered by a wide range of environmental designations. In particular Brownsea Island and the western side of Poole Harbour support internationally important bird reserves that are easily disturbed by excessive noise and activity.
Operational. The routine operations, maintenance and refit of equipment pose risks for wildlife through disturbance and direct physical impact such as rotor blade strikes. With the exception of blade strikes (see ‘Negative impacts’ and ‘Rotors’ below) this phase, once operational stability has been achieved, is less likely to be a serious concern. There remains a concern over the potential for non-native invasive species, such as Undaria pinnatifida, which is already well established in Poole Harbour and the Solent, but not yet on the seabed in the open sea, to spread from the construction/servicing port to the turbine array and then to the wider environment.
Decommissioning. All subsea materials to within 1 m depth of the seabed need to be removed at the end of the wind park life. Within-substrate structures may be better left in situ because their removal operations may cause more environmental damage than their abandonment. A bond in the form of a deposit should be established at the start of the project that would fund decommissioning should the operator get into financial difficulties. A model for this, both good and bad, is provided by the North Sea oil & gas industry. A plan for removal, including impact assessments needs to be lodged prior to project approval.
5. Structural elements
The following main structural elements of the development are of varying levels of concern for DWT:
Footings. The type of footings have yet to be chosen, but will comprise either piles or a gravity base (held down by its own weight). The former will have serious sound / vibration impacts during
construction and will need considerable mitigation. A gravity base will smother the substrate over the footprint on which it stands, but this will be a small proportion of the total seabed of the area.
Rotors. These are a primary concern for DWT as they are likely to cause strikes with flying species. DWT expects that the operator will monitor strikes throughout the operational phase and take remedial action if these prove to have harmful impacts on species populations especially local populations. It may for example be necessary to stop the rotors during periods of peak migrations, as indicated by observation rather than inherently uncertain estimates of expected migration periods.
Subsea cables. It is likely that subsea cables will be trenched and backfilled for their own protection. This will also reduce electro-magnetic force impacts on elasmobranchs. The trenching process can cause significant quantities of suspended solids that are damaging for filter feeders and can smother plants and sessile animals. DWT expects that solids transport will be minimised particularly in hard substrate areas with sessile organisms.
Onshore cables and facilities. The cable route is planned to go through several designated areas, primarily heathland, as well as across the River Avon. This will be one of the most serious impacts of the development. DWT seeks assessment of habitats and working methodologies to determine the least damaging construction methods and most effective restoration of sites and biodiversity gains within the scheme. DWT will expect the developers, irrespective of minimum legal requirements, to ensure best practice methods, such as directional drilling under river systems, are employed so that wherever possible designated sites are avoided completely and that it can be ascertained that the proposal will not adversely affect the integrity of any internationally designated site. If unavoidable, mitigation of impacts on important but non-statutory sites is preferable to compensation. Sites will need to be restored to their former quality, and funding from the development used for their ongoing maintenance and that of the wider area.
The same principles apply to facilities such as new sub-stations.
Protected species also occur outside of designated sites and will require due consideration and protection.
The construction base. Impacts at the site of the construction base where materials are stored and turbine infrastructure is assembled are as important as the wind park itself. The base has yet to be chosen and would be expected to be used during all phases of the project, not just construction. Impacts that need to be minimised include noise, vibration and physical damage within the development footprint should new facilities be required. Particular care will be needed to establish sufficient ballast water treatment and hull cleaning facilities to reduce the spread of invasive species depending on the source of the materials.
Land-based transport infrastructure. Road links to Poole and Portland have been identified by the Dorset Local Enterprise Partnership (LEP) as amongst their priorities for improvement. Roads to both locations pass through important designations and so great care will be required to ensure damage to the natural environment is avoided and mitigated. DWT will campaign for a net gain in biodiversity for all developments.
6. Natural benefits
DWT supports the benefits of renewable technologies that reduce the greenhouse gas emissions that are leading to climate change and ocean acidification. Additionally there are several possible local scale positive impacts on the natural environment that would be expected from the development.
Protection for pelagic and demersal fish populations. The UK, like most of the world’s countries and seas, has suffered from over a century of commercial overfishing that has decimated fish populations with disastrous knock-on effects for the wider ecosystem and the viability of the
fishing industry. Marine Protected Areas (MPAs) are being designated at a national and European level and have been shown to be highly successful at restoring both sites and fisheries. If exclusion zones around each turbine are established they will act as de facto MPAs and contribute to the network of protection that is so important around the UK coast. It is likely that habitats (Sheehan, et al., 2013) fisheries and fishermen will benefit in the medium to long term, as they have done in the Lyme Bay exclusion zone, as fish grow larger and have a greater chance of breeding success. It is though likely that there will only be exclusion zones of 500m during the construction phase and there may be zones of 50m (corresponding to the area taken up by a gravity base structure) only if DECC require it. 50m zones would represent less than 1% of the total area at only 1.7km2.
ï‚· Creation of artificial reefs. It is well documented that artificial reefs attract mobile species, particularly pelagic fish, but also crustaceans. The footings of the wind park may not add to the number of fish in a population in the short-term, but they will probably concentrate them in protected areas within the turbine exclusion zones. It may be possible to use the footings as a site for the restocking of crustaceans such as edible crab and lobster, which has occurred on artificial reefs in Studland and Weymouth Bays. As suitable habitat is unlikely to be lacking in the area, it is the possible protection afforded, such as from dredging and trawling, that may produce the benefit rather than the rocks themselves. There are pros and cons to the creation of hard substrate where there was previously none or little. On the positive side this may lead to an increase in biodiversity by offering a wider range of habitats. On the negative side the natural habitat is lost and changed.
On-shore biodiversity enhancements. There is scope for this scheme to provide biodiversity enhancements by restoring and linking habitats. For example, areas of low ecological value within forestry plantations could be restored to heathland/acid grassland and associated habitats through sensitive pine/scrub removal and long-term management to create corridors connecting designated sites.
Provision of data. The development team will need to conduct a wide range of surveys prior to application, during and after the operational phase. Such data will be extremely useful to aid our understanding and management of species and habitats in the area. DWT therefore expects that this data will be of a sufficiently high quality and will be made openly and freely available and will be provided to the Dorset Environmental Records Centre.
7. Potential negative impacts on habitats and species
This section lists possible impacts on a range of terrestrial and marine habitats and species. At this stage DWT is not stating that all of these impacts would occur were the development to go ahead, but that they could occur if the development is not well planned and suitable methods and mitigation are not employed. Some may prove unavoidable and this possibility is discussed in Section 8.
Bats. In terms of offshore wind development, the main potential threat to bats is to any which have major migratory patterns through the turbine area. The onshore development area needs to be assessed for potential impacts on bat roosts and foraging, but such impacts should be possible to mitigate with careful planning. At this stage the extent of likely migration of UK species across areas of sea has not been quantified. The bat species at high risk from onshore wind turbines are Nathusius’ pipistrelle, Leisler’s and Noctule. Of these, we know Nathusius’ pipistrelle does migrate across the Channel, but the extent of this, and migration of other species, is still being researched. There is a lack of data particularly during migration periods. Realistically, significant impacts on bat populations are unlikely because the rotors are not within a multi-pass foraging area, as opposed to a single pass migration route.
Birds. Impacts on heathland migrants such as nightjar, hobby, merlin and hen harrier are critical because they move to and from their bases in Dorset and the New Forest. Impacts on heathland are difficult to assess. Two summer migrant species, hobby (Schedule 1) and nightjar are of particular concern. It is proposed to undertake land-based construction operations outside the nesting season, but onshore heathland operations in winter may potentially impact on two other Schedule 1 species, i.e. hen harrier and merlin. Additional modelling has apparently been conducted for nightjar, though not yet reviewed by DWT. Hen harrier and merlin are winter visitors and passage migrants into Dorset with probably limited movement from the near continent. The Dorset population is mostly found in the Poole basin. Nightjar and Hobby may pass through the turbine area on annual migration, though little is known about nightjar movements such as time of day and height, etc, hence the additional report was commissioned.
Of particular concern is the damage to migrating birds and resident seabirds that have sensitive or small local populations. These populations would be at risk from collision with rotors. The developer has conducted surveys and constructed somewhat more conservative worst-case models (95% rather 99% probability of impacts – preferable from a conservation perspective). Many of the resident seabirds may be expected to move repeatedly through the project area throughout the year. It is not the overall number of strikes, assessed against nationally occurring populations, that is of greatest concern, but rather the impact on local populations, e.g. gannets from Alderney which houses 2% of the world population and which forage in the proposed wind park area.
The low level of records of both seabirds and other migrants, based on monitoring and modelling, is a critical issue. Ornithological surveys submitted by the developer were though professional and robust.
Flying invertebrates. This is not thought to be a major consideration.
Temporary disturbance to seabed habitats during construction – including preparation of the seabed prior to installation, impact of the feet of jack-up barges, cable-laying and cable-vessel anchoring – these are direct physical impacts and habitats may fully recover in time.
Temporary increase in suspended sediment concentrations – from ground preparation, piling, drilling, cable trenching/jetting. Fine sediment from chalk drilling is of concern as it is known to persist longer than other sediments. The impacts include increased turbidity/reduced available light affecting photosynthetic species and clogging or abrasion of filter-feeding apparatus of benthic organisms. When the increased sediment settles out of the water column, there is the potential for smothering of benthic organisms, particularly close to the site of the works. This could also affect spawning fish
Net loss of seabed habitat – caused by placement of turbine bases, scour protection and cable protection material.
Habitat change – in many cases the seabed habitat is changed by replacing a sediment seabed habitat with a hard substrate – be that rock armour of the turbine base itself. This new habitat will extend to the surface, in the case of turbine bases and a zonation of communities is expected to develop. One particular concern over this array of new habitats is the potential to act as stepping stones for the introduction and subsequent spread of non-native species.
Hydrodynamic changes – the placement of an array of large structures on the seabed is likely to have a localised effect on water movement and sediment transport, including scouring around the turbine bases.
Underwater noise – particularly that caused by piling operations. This can cause injury or mortality to fish and marine mammals close to the piling activity and is likely to cause many mobile species to move away. The deterrent effect of the piling noise may affect spawning migrations of some species.
Increased vessel activity – an increase in vessel movements between construction base/servicing base and the wind-farm will increase the opportunity for collision with marine megafauna. There is a particular concern about seals and fatal “corkscrew” injuries which are thought to be the result of impact with ducted propellers, often used on vessels with a dynamic positioning system
Soft substrate marine species. As stated above, there are 3 main types of impact on these animals: direct covering by the footings; smothering by suspended solids from trenching and other activities; damage to filter feeders through inert suspended material. As described above, DWT expects that the developer will monitor the extent and abundance of such populations and minimise solids transport.
Marine filter feeders. These species groups such as hydroids, bryozoans, sea squirts and sponges are particularly sensitive to seabed activity on soft substrates. The feeding structures become swamped by inert material from solids suspended by development activity. These solids have a low nutritional value and so the animals become energetically compromised. The filter mechanisms may also become blocked in extreme cases. As stated above, DWT expects that populations will be surveyed and monitored and remedial action taking if damage occurs. It is also expected that the suspension of solids will be minimised.
Fish and cetaceans. The primary impact of concern to DWT on these species will be disturbance and possibly death caused by piling noise (vibration). Of particular concern will be seismic and piling operations (see above), though greatly increased ship traffic may be an issue, e.g. to seahorses in Studland Bay and Poole Harbour. While fish may be less disturbed by day-to-day operations, cetaceans are more likely to be disturbed. It is expected that high energy noise will be minimised and mitigated, the effect monitored and remedial action taken, such as seasonal stoppages.
Heathlands. The main impact on heathland and associated habitats would be habitat loss and damage during the construction and decommissioning phases, particularly where open trenches are cut for cable installation. In addition, fauna may be disturbed or displaced and surrounding habitats degraded through release of dust and pollutants. DWT supports trenchless crossing techniques to avoid or minimise damage and disturbance to the most sensitive sites. It should be noted that in forestry plantations, it is the rides or beneath power lines where the most valuable surviving heath habitat is likely to occur. DWT expects the developers to employ mitigation and best working practices to minimise impacts such as: a very strict protocol to work at the least damaging time; to keep the working width to the minimum; to keep dug material separated from the intact surface; and humus (with seed bank), soil and subsoil all to be kept separate, stored for minimum time and each replaced in the correct sequence.
Rivers and streams. The scheme could cause significant impacts on the River Avon and its floodplain grassland which supports overwintering birds, and the Moors River. Trenchless crossing techniques could avoid or minimise damage and disturbance to this habitat and species. Mitigation is also expected to minimise or avoid the risk of pollution.
On-shore protected and key species. All six native reptiles, amphibians, badgers, otters, water voles, bats, dormice and scarce aquatic invertebrates are known to occur on or near the on-shore route and could be affected either through direct impact resulting in death or injury, or through loss of habitat. Mitigation measures will be required to ensure these species are protected and impacts minimised.
8. Compensation
The goal of biodiversity offsetting or compensation is, “To achieve no net loss and preferably a net gain of biodiversity on the ground with respect to species composition, habitat structure and ecosystem function and people’s use and cultural values associated with biodiversity.”
DWT’s position is that if the development is approved, the standard protocol for dealing with negative impacts must be employed, i.e. in order of decreasing preference: avoid, reduce, restore, offset.
Certain impacts such as the death of cetaceans must be entirely avoided and tests under UK law and EU Habitats Regulations will need to be met in respect of protected species. There are also well-established procedures for many forms of mitigation.
DWT believes however that it is not sufficient to either just avoid and mitigate impacts, though avoidance is of course the preferred route whenever possible. There must, with all developments, be a net gain for biodiversity, not merely a status quo. Services are being provided by the natural environment with a commercial economic benefit. Such a benefit is entirely acceptable, but as with the provision of services from supporting companies, these benefits should be remunerated. In this way resources can be put into the natural environment to manage it in a sustainable way and in many cases restore the natural function (e.g. fisheries or heathland) to the benefit of species, habitats and future human exploitation.
It is DWT’s view that a significant, but not commercially damaging fund needs to be established, along the lines of ecosystem credits. This fund should be established as a small but significant percentage of operating profit managed by independent bodies such as the government established Dorset Local Nature Partnership (LNP) and Solent LNP with representatives from industry, local authorities, agencies and NGOs. Not only would this benefit the environment which underpins all development, but it would benefit the operators and greatly assist their commercial case. A similar precedent has been established by the landfill industry with great success for all parties.
9. Consultation
Consultation is an important but onerous process for the consultees. The developer must understand that most individuals and organisations have limited capacity to respond and allow sufficient time for a meaningful response. Any primary research required to establish likely ecological impacts, where these have not already been researched adequately elsewhere, should be funded by the developer. The onus should lie with the developer to demonstrate that their proposal is appropriate rather than NGOs such as DWT being expected to fund studies into potential impacts. DWT further expects that sensible, useful responses will be acted upon and that the consultation exercise is open, transparent and genuine, not merely a means to get out information and tick a consultation box. Dorset has a long reputation of collaborative working exemplified by organisations such as the Dorset Coast Forum, that will aid a genuine consultation.
10. Conclusions
- DWT can only comment on the wildlife and natural environment implications of this development. Our aim at this stage, with the information available, is to clearly state our expectations rather to pass judgement as to whether the development should progress.
- DWT is in principle supportive of renewable energy development that will reduce emissions of greenhouse gases because climate change and ocean acidification are imminent threats to species and habitats in Dorset and around the world. This does not however mean that DWT will agree that every proposal is appropriate or acceptable. A net gain for nature is an essential requirement.
- There are several phases of the development and elements of the infrastructure that are a concern for DWT as they may adversely impact the natural environment.
- It is possible that there will be marine ecosystem benefits from the development primarily resulting from the physical protection of mobile species from capture afforded by the small areas of restricted access around the base of the turbines.
- The provision of hard marine habitat, different from that currently present, is likely to increase biodiversity, but that is not necessarily advantageous if the background habitat is artificially altered.
- The developer has conducted some detailed bird surveys and constructed robust worst case models, however it is not the overall number of strikes within a national population alone that is of concern, but rather the effect on the local population especially if it is small or vulnerable, such as Alderney’s gannets.
- The lethal and sub-lethal effects of high energy noise on cetaceans and fish during construction of the footings is also a concern.
- There must be a net gain for the environment on which this development is dependant. A small but significant percentage of operating profit should be put back into the environment.
11. References and further reading
BBOP (2012a). Standard on Biodiversity Offsets. Available at: https://www.forest-trends.org/documents/files/doc_3078.pdf.
BBOP (2013). To No Net Loss and Beyond: An Overview of the Business and Biodiversity Offsets Programme (BBOP). Washington, D.C. Available at: https://www.forest-trends.org/documents/files/doc_3319.pdf.
Blyth-Skyrme, R. (2010). Options and Opportunities for marine fisheries mitigation associated with windfarms. COWRIE report.
DECC (2011). National Policy Statement for Renewable Energy Infrastructure (EN-3).Defra (2012a). Biodiversity Offsetting Pilots. Guidance for developers. March 2012. Available at: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/69528/pb13743-bio-guide-developers.pdf.
Natural England (2010). Guidance Note: European Protected Species and the Planning Process, Natural England’s Application of the ‘Three Tests’ to Licence Applications.
Natural England (2012). TIN051: Bats and onshore wind turbines, interim guidance.
Navitus Bay (2013). Proposed Navitus Bay wind park. Phase three community consultation February 2013. Navitus Bay Developments Ltd, 50pp.
Navitus Bay (2013). Preliminary Environmental Information 3 (PEI3).
HM Government (2011). UK Marine Policy Statement.
Sheehan, E., et al. (2013). Recovery of a temperate reef assemblage in a marine protected area following the exclusion of towed demersal fishing. Plos One, 8 (12), 1 – 12.
The Planning Inspectorate (2013). Advice note ten: Habitat Regulations Assessment relevant to nationally significant infrastructure projects.
12. Further information
Authors
Simon Cripps, Peter Tinsley, Imogen Davenport, Nicki Brunt & Chris Thain
Contact
Peter Tinsley
DWT email
Web
www.dorsetwildlifetrust.org.uk
Revision date
Dependant on the progress of the proposal