Duddon Estuary Tidal Energy

Technical Summary

All photographs, drawings and graphics copyright of their originators, whose permission to reproduce is gratefully acknowledged.

Duddon Tidal Energy Study

• Alignment Options

Potential Options

• Energy Yield From Potential Options

Environmental Considerations Nature Conservation Status

© Crown Copyright: (MAgiC)

• Key interest features• Intertidal mudflats and sandflats• Pioneer and established saltmarsh• Internationally important populations

of ‘Annex 1’ bird species• Internationally important populations

of regularly occurring migratory species

• Internationally important assemblage of waterfowl

Morecambe Bay & DuddonEstuary European Marine Site

• “Natura 2000” conservation network

• Morecambe Bay SAC• Duddon Estuary SPA & Ramsar

Redshank and Knot

© British Trust for Ornithology / Nigel ClarkSandscale Haws towards Askam

Environmental Considerations Nature Conservation Status & Flood Risk

Duddon Estuary Ramsar• Wetland site of international importance• Nationally important numbers of the rare

Natterjack Toad (18% of British population)• Rich assemblage of rare wetland plants and

invertebratesOther environmental receptors

• The Estuary and its rivers have generally good water quality

• Listed major salmon and sea-trout fishery• Low level of commercial fishing activity• Marine mammals

Flood Risk• Areas around the estuary are at risk of

flooding under a 1:100 year scenario including urban areas, railway and A-roads

• Barrage could offer reduced flood risk benefit• Potential protection from surge tides

Environmental Considerations The Estuary Environment & Potential Project Effects

The Estuary• Mostly sandy with some muddy sediments• Highly dynamic estuary - influencing nature of

the benthic invertebrate communitiesKey considerations for the project

• Effects on estuarine and marine fishCommercial & recreational fishing

• Appropriate Assessment will be required• Reduced intertidal area and exposure time • Most affected area is also key bird habitat,

including Scarth Bight and up to Askam• Differences in effects between conventional

barrage and the low head barrage• Response of Estuary under a new regime• Natterjack toad breeding area

Potential impacts upon the inundation regime and groundwater levels

• Effect on “Landscape of County Importance”Average number of all waterfowl species combined feeding at low tide on each count area (winter 1991/92)

Preferred Alignment

• Water Levels and Power Generation – Springs

Preferred Alignment

• Loss of Inter-tidal Habitats (simplified assessment based on MLWS and Preferred Alignment)

Existing Spring tide

Before After

Habitats Directive

• Habitats Directive• A Habitat Regulations Assessment (HRA) is likely to conclude that legally

protected sites within the Duddon Estuary would be affected. Consequently the HRA would need to consider whether

• there were any less damaging alternatives, • There are over-riding reasons of public interest to take forward a

scheme and• The feasibility of providing compensation to maintain the coherence of

the Natura 2000 network

• For the purposes of this study, compensatory habitats are assumed to be feasible but specific sites have not been identified. Costs have been estimated on the basis that:

• There is a net loss of 4sq km of inter-tidal habitat within the Special Area of Conservation (SAC) under the Habitats Directive

• A replacement ratio of 2:1 would be required as new habitat would not be as effective as existing habitats

• A cost of £65,000 per ha is used for land purchase and construction of compensatory habitats.

Regional Considerations

• Regional Issues

• Impacts on existing estuarial users• Fishing• Navigation• Visual• Disruption during construction

• Opportunities• Tourism• Improved flood risk• Economic Development from better transport links, including improving supply chain

opportunities for new Nuclear in Cumbria• Employment – during and after construction – direct and indirect • Removal of through traffic from sensitive areas

Duddon Tidal Energy Study

Assessment Framework

Proposed Barrage Option

• Plan – Haverigg to Sandscale Haws

Sandscale Haws

• National Trust own Sandscale Haws and landing a Barrage on Sandscale Haws is therefore challenging

• Alternative landing sites are not available• An indicative technical solution to landing at Sandscale Haws has been identified to

inform the study.

Embankment morphs into a beach as it transitions to Sandscale Haws

Road crossing diverges from embankment and is carried on a shallow bridge to the shore

Proposed Barrage Option

• Cross Section through embankment

Proposed Barrage Option

• Cross Section through Turbine Caisson

Proposed Barrage Option

• Cross Section through Sluice Gate Caisson

Transport Links

• Key Drivers:• Improved road access to Sellafield and new nuclear build – particularly

from potential supply chain at Barrow / Vickers• Reduction in local journey times• Reduction in accidents• Bridge vs reduction in cost if aligned with a tidal energy structure in the

Duddon

• Key Challenge• What is the preferred route (with or without a tidal power scheme)?

• Study Conclusions• The additional cost of providing a bridge rather than a barrage to achieve

a transport link across the Duddon Estuary is approximately £140m.

Conclusions

A Tidal Barrage generating 280GWh per year is technically feasible and could be constructed by 2020 (at the earliest) at acost of between £650m and £750m

• Progress in developing tidal energy from the Duddon would be subject to many commercial and environmental / regional considerations

Conclusions

• Commercial Considerations:• DECC Marine Action Plan (March 2010) is assuming a cost of £229/MWh @ 8% for non

Severn tidal range potential by 2050.• Current energy cost estimates for Duddon are similar, particularly if credit is applied for the

construction of a new road crossing• As embryonic technologies develop (eg low head turbines and venturi fence), this may

reduce cost of energy – to be confirmed following subsequent research – but would not be ready in same timeframe.

• Environmental and Regional Considerations• Landing zone at Sandscale Haws requires careful attention• Uncertainties relate to impact of tidal energy on, inter-alia, natterjack toads, protected bird

species, fish, saltmarsh, inter-tidal habitat loss and associated mitigation / compensatory measures

• Geomorphological change and rate of sedimentation are also key areas of uncertainty• Other regional tidal power schemes may have an impact on energy yield from the Duddon• Navigation requirements may change depending upon Millom Port’s success in securing

work arising from the offshore wind sector.• Benefits include reduced flood risk from storm surges and sea level rise, improved travel

times and road safety, increased direct and indirect employment during and after construction.