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EspañolSEVERN BARRAGE
Barrage locations considered over the years
The 'Severn Barrage' is the name of a number of ideas for building a barrage from the English coast to the Welsh coast over the Severn tidal estuary. Ideas for damming or barraging the Severn estuary (and Bristol Channel) have existed since the 19th century. The purposes of such a project has typically been one, or several of: transport links, flood protection, harbour creation, or tidal power generation. In recent decades it is the last that has grown to be the primary focus for barrage ideas, and the others are now seen as useful side-effects.
The building of such a barrage would be a huge engineering feat, comparable with some of the world's biggest construction projects. The huge size and cost of most of the ideas over the years are what have kept plans firmly on the drawing board.
Various projects
There have been numerous proposed projects over the years, some more rational than others.
Thomas Fulljames - 1849
Thomas Fulljames's own impression of his proposed Barrage
Thomas Fulljames proposed a barrage from Beachley to Aust (now the site of the first Severn crossing), a span of just over a mile. Since this was before serious electricity demand, the first proposals were based on the desire for a large shipping harbour in the Severn Estuary, and also railway transport and flood protection.
Study - 1925
In 1925 an official study group was commissioned. A scheme of 800MW was proposed at English Stones and although considered technically possible, it was prevented on economic grounds (then costing £25 million).
Prototype - 1931
Paul Shishkoff, a Russian immigrant, demonstrates a 300 horsepower prototype tidal generator at Avonmouth. It included a novel mechanism to spreading the power output over 24 hours. The full barrage was estimated at £5 million at the time.
Severn Barrage Committee - 1933
In 1933 the Severn Barrage Committee (HMSO) Report recommended that a barrage across the English Stones area would be the best option.
Nazis - 1940s
The Nazis drew up plans for a barrage for when they had conquered Britain.
Study - 1948
The Government looked at barrage options. Cost estimated at £60 million.
Study - 1953
The Government looked at more barrage options. Cost now estimated at £200 million.
Tom Shaw - 1971
Tidal Power expert, Dr Tom Shaw, proposes a barrage from Brean Down to Lavernock Point. Estimated cost £500 million.
CEGB - 1975
In 1975 the Central Electricity Generating Board (CEGB), published a study with evidence from Bristol and Salford universities for the Secretary of State’s Advisory Council on Research and Development for Fuel and Power. As this was the era of cheap oil, the council established that a barrage could not be economically viable unless the energy situation deteriorated significantly.
Severn Barrage Committee - 1981
Proposed location of Bondi Committee Barrage
After just such a deterioration (due to the Iranian Revolution and oil shock) the plans were reinvestigated by the ''Severn Barrage Committee'' in 1981. This committee was known as the 'Bondi Committee' (after Professor Sir Hermann Bondi). The committee investigated 6 possible barrage locations, from English Stones at the top of estaury, down to a location largely at sea in the Bristol Channel between Lynmouth in North Devon and Porthcawl in South Wales. It produced a major energy paper , which recommended a 16 km long barrage of concrete powerhouse between Brean Down and Lavernock Point, sluice and plain caissons together with sand and rock-fill embankments. It would have generated 7200 MW on the flow of the tides (the largest barrage considered could have produced double that power output). This set of plans was strongly built on a few years later by the Severn Tidal Power Group.
Wimpey Atkins - 1984
Wimpey Atkins proposed a smaller barrage at English Stones, in the hope of creating a smaller more economically viable project that would avoid the environmental impact of a large barrage.
Hooker Barrage - 1987
Cross section of Shoots Barrage turbine housing
Arthur Hooker OBE (a former partner of WS Atkins) in conjunction with Parsons Brinckerhoff prepared a revised barrage proposed at English Stones to better tackle the issue of silting, after the earlier Wimpey Atkins scheme in the same location had been criticised by an STPG study for this reason.
Parsons Brinckerhoff further updated this proposal in 2006 and current estimates for this barrage (now known as the 'Shoots Barrage') would cost £1.4 to £1.8 billion to build, and generate 2.75 TWh of power per year. At the highest tidal range, it would develop a peak output of 1050 MW, and 313 MW output on average throughout the year. Thus the Shoots Barrage is about 1/7th of the size and cost of the SPTG proposals.
Cross section of embankment
The barrage would be located just below the Second Severn Crossing; i.e. above Cardiff and Bristol on the estuary - and so much smaller locks would be needed for upstream access to Sharpness and Gloucester docks as the large ports of Portbury and Avonmouth would be unaffected.
Like the SPTG proposal, Hooker generates only on the Ebb tide. Construction time would be 4 years. It would be built of rockfill embankment at the coastal sides (more like the proposals for "Tidal Lagoons"), but like the STPG would be sluice Caissons and turbines with powerhouse in the middle section.
Severn Tidal Power Group - 1989
The £4.2 million study by Severn Tidal Power Group (STPG) built on the work of the Severn Barrage Committee, but also examined other possible barrages, and produced another major energy paper . They concluded that the 1981 plans were the best location for a barrage, but calculated that the power output could be larger, at 8640 MW during flow, or 2000 MW average power. This would provide 17 TWh of power per year (about 6% of UK consumption), equivalent to about 18 million tons of coal or 3 nuclear reactors. The cost in 1989 was calculated to be about £8 billion (£12 billion in 2006 money - about the same as 6 nuclear reactors, but different lifespan), and running costs would be £70 million per year (about the same as 1.5 nuclear reactors).
Diagram of the STPG Barrage
The barrage would use existing technology as used in the Rance tidal barrage in France and the Dutch sea barrages. Power would be most efficiently generated only in the flow direction, and this effect on tidal range would mean that the tidal extent would be halved by losing the low tide rather than the high tide. That is, that the tide would only go out as far as the current tidal mid-point, but high tides would be unaffected (unless the barrage was deliberately closed to prevent a high-tide).
Construction in prefab caissons
The barrage would contain 216 x 40 MW turbines for the 8640 MW total. Arrays of sluices would let the tide in and then close to force it out through the turbines after the tide has gone out some distance outside the barrage. This deliberate building of a ''head'' on the water builds pressure that makes the turbines more efficient.
Artist's impression of cross-section
The barrage would contain a huge set of shipping locks, designed to handle the largest container vessels. Construction would take about 8 years and would require 35,000 employees at peak build time. The minimum lifespan of the barrage would be 120 years (about 3 times that of a nuclear reactor), but could easily be 200 years if decent maintenance was performed.
Artist's impression of aerial view of STPG Barrage
The STPG appraisal concluded that the electricity generated from the barrage would make the scheme economically viable if given certain "green" advantages, and that the environmental impact was acceptable. Margaret Thatcher's government did not accept this, and shelved the plans. However, since then global warming has radically altered the public perception of environmental damage; and soaring oil, gas and energy costs have made the economics of the barrage much more favourable. The advent of renewable energy discounts favours electricity generated from "green" sources; and in addition, much lower interest rates make the cost of loans much lower, and long-term financing of such massive projects is now more viable. Consequently, there have been renewed calls for these plans to be re-appraised.
Gareth Woodham - 2006
In 2006 Gareth Woodham, a businessman from Neath in Wales, submitted plans to Sedgemoor District Council in the name of Combined Innovations Ltd for a barrage from Brean Down near Weston-super-Mare, to Lavernock Point near Cardiff [1]. According to Woodham, the barrage would feature 14 electricity generating turbines, a dual carriageway, a light-railway, four marinas, and two lock gates to give ships passage. It would supply electricity for the whole of the South West, and according to Woodham it would cost about £650 million and take up to 20 years to complete.
However, it isn't clear how Woodham's plans, which are more ambitious than those of the STPG, can be delivered for 1/20th of the cost.
Benefits and Disadvantages
Benefits
★ Predictable source of "green" energy during lifetime of barrage
★ Home-grown facility, independent of foreign uncertainties
★ Flood protection for the vulnerable Severn estuary, including against global warming sea level rises
★ Transport links for road and/or rail
★ Better shipping and boating conditions behind the barrier
★ Boost to local economy - construction industry in the short term, tourism and infrastructure in the long term
★ Reduced turbidity (cloudiness) of water will improve the density and spread of invertebrate colonies in the estuary. This should lead to better carrying capacity for migratory fish and birds.
Disadvantages
★ Existing ecosystems would be heavily altered, with new species moving in and perhaps dominating old species
★ Some of the low-tide mud-flats would be lost, displacing some of the wading birds that make the estuary a protected area
★ Enormous project of a size that the UK is unused to dealing with
★ Likely to stimulate silting in some areas and coastal erosion in others
★ Enhance flood risk on the seawardside because only a proportion of the water that presently flows up stream will pass through the barrage leaving the remainder to rise up outside possibly raising levels by as much as a metre.
★ Shipping would have to navigate locks
★ Severn bore weakened
★ All industry discharges into the Severn (eg Avonmouth) will have to be reassessed.
Dangers?
Unlike river dams, there is no danger associated with collapse of a tidal barrage. If a freak earthquake (or a ship collision) were to break the barrage, the water would flow out (or in) at the speed of the tide, just as it does now, and just as it would during construction. This would only represent a danger to those caught directly in the current, as it does now.
Environmental impact
The Severn Estuary is a Special Area for Conservation due to the European importance of its ecology. The inter-tidal area provides food for over 85,000 migratory and wintering water birds, and represents 7% of the UK's total estuaries.[2]
The Barrage was not supported in the 2003 Energy Review due to "strong environmental concerns" (The same paper also described nuclear power as "an unattractive option"). [3]
The RSPB opposes any Severn Barrage because of the effect it will have the feeding grounds 85,000 birds depend on, stating "The impact a barrage would have is huge. This is one of the most important sites in the UK for wild birds and the chances of them surviving if it went ahead are fairly slim. There wouldn't be enough room left for all the birds and there wouldn't be enough food for those that remained. The estuary is one of the UK's most important sites for water birds and its wildlife value must be taken fully into account"[4]
Possible effect of turbidity reductions in Severn Estuary
The present strong tidal currents in the estuary serve to lift up silt sediment and so keep the water thick with fine particles. This blocks light-penetration and means that the Severn Estuary marine environment is actually a relative desert, in terms of both plant and fish life (Kirby and Shaw 2004, Proceedings of the ICE) .
The barrage will not create a "lagoon" - as both opponents and supporters have sometimes claimed. Tidal power stations by definition require that the tide flows through the barrage, but the tidal range in the Severn would be halved.[5]
DEFRA claims that the environmental effects of the barrage still need more analysis before final conclusions can be drawn. The Sustainable Development Commission is investigating UK tidal resources, including tidal power in the Severn Estuary and its environmental impact, and should report mid-2007. [6]
Tidal lagoon alternative
Friends of the Earth support the idea of tidal power, but oppose barrages because of the environmental impact. They have proposed their own plans based on the concept of ''tidal lagoons'' (see references), whereby man-made lagoons in the estuary would fill and drain through turbines. Their proposals would include lagoons covering up to 60% of the area covered by the barrage, which in some smaller configurations would not impound water in the ecologically sensitive inter-tidal areas of the estuary. The lagoons could be sub-divided so power would be generated at more states of the tide than a barrage, with lower peak output, giving economic advantages to set against the higher construction cost of longer barriers. This idea is based on a prototype now being designed at Swansea bay. However leading figures in the construction industry are sceptical that the lagoons can be economic.[7]
Effects of different site locations
One of the complicating factors in assessing the impacts of a barrage is the large number of possible locations and sizes for the barrage. Generally, the larger the barrage the bigger its environmental impact, and the bigger the amount of energy it could create - and therefore the bigger climate change offset it could have by way of its renewable power generation.
The largest barrages (sited beyond Hinkley Point and towards Minehead) would significantly affect the entire Severn Estuary and much of the Bristol Channel, but could generate 15 GW peak power and protect the whole of the Somerset levels against flooding and sea-level rise caused by Global Warming. The smallest barrages (sited at Aust/Chepstow) would affect only the river and estuary in Gloucestershire, but would also only generate perhaps 0.75 GW peak power.
Construction costs
The estimated costs of the most recent plans are huge - perhaps £10-15 billion. However, the recent plans have assumed that the project would be privately financed, and so in effect the matter of cost becomes a private one between the building consortium and their banks. If the banks feel that the project is viable and decide to lend the money then the projects will go ahead. None of this cost would directly fall on the tax-payer. There would though be secondary knock-on costs from the barrage that might be met by the tax-payer, such as modifying existing ports and dealing with environmental change. However, these would be offset by the positive knock-on effects, such as transport links and flood protection - which would have otherwise also cost tax-payer money. Whether the parties actually decided to exchange monies for these knock-on effects would be a matter for Government negotiation.
Vested interests
It has been suggested that powerful construction industry based vested interests are the main force behind Severn Barrage proposals. Clearly, any project with a budget of several billion pounds will rouse numerous vested interests both for and against it. However, in order to understand where the vested interests might lie, it is necessary to see the wider picture. The alternative to any Severn Barrage would probably be three nuclear power stations; and these are huge facilities that would have to be built by someone - the same construction industry that stands to gain from the barrage. Friends of the Earth state that their proposals for "lagoons" would require 20 times as much construction material as the Barrage to build, and so should be even more desirable for the construction industry if driven by vested interests. In the end, the vested interests of those wanting the Barrage built will come up against the vested interests of those who do not want it built; and these include not only bird protection and environmental groups, but also the nuclear and oil industries.
Opinions
Backers
★ The former Prime Minister of the United Kingdom, Tony Blair [1] (who backed it in the last weeks of his tenure)
★ The Secretary of State for Wales, Peter Hain
★ The Welsh Assembly
★ The Commons Welsh Affairs Select Committee
★ Welsh First Minister, Rhodri Morgan[2]
★ The South West Regional Assembly
★ Weston Super Mare MP, John Penrose[3]
★ Cardiff Central MP, Jenny Willott[4]
★ Northavon MP, Steve Webb[5] [6]
★ Ogmore MP, Huw Irranca-Davies[7]
★ Kingswood MP, Roger Berry[8]
★ Bristol City Council has passed a motion calling for an urgent reappraisal [9]
★ Bristol West MP, Stephen Williams has also said that the project must be urgently investigated, and has proposed an EDM on the subject[10][11]
★ North Somerset Council has also called for a new appraisal[12]
★ Scientist and "Gaia" theorist, Dr James Lovelock CBE[2]
★ The Minister for Local Environment, Marine and Animal Welfare at Defra, Ben Bradshaw[14]
★ The Secretary of State for Environment, Food and Rural Affairs, David Miliband, has said that the project "Has to be worthy of very serious consideration" [15]
★ The Secretary of State for Trade and Industry, Alistair Darling [16]
Opponents
★ Former UK Science Minster, Lord Sainsbury
★ MP for Woodspring, Liam Fox
★ Bristol Green Party[17]
★ Gloucestershire Green Party [18]
★ South West Green Party [19]
★ RSPB Cymru[9]
★ Friends of the Earth Cymru[9]
★ World Wildlife Fund Cymru [22]
★ Gwent Wildlife Trust[23]
★ Avon Wildlife Trust[24]
★ Political commentator, George Monbiot[25]
See also
★ Energy policy of the United Kingdom
★ Energy use and conservation in the United Kingdom
References
★ "Tidal power from the Severn Estuary"-Volume 1: Energy Paper 46; HMSO 1981
★ "The Severn Barrage Project: General Report": Energy Paper 57; HMSO 1989
★ Kirby, R. and Shaw, T.L. (2004) "Severn Barrage, UK – environmental reappraisal" Proceedings of the Institute of Civil Engineering
1. http://thisisbristol.co.uk/displayNode.jsp?nodeId=144936&command=displayContent&sourceNode=144919&contentPK=17565890&moduleName=InternalSearch&formname=sidebarsearch
2. http://news.bbc.co.uk/1/hi/wales/5039918.stm
3. http://www.epolitix.com/EN/MPWebsites/John+Penrose/46df5559-c191-4af4-bf06-4a53a0192893.htm#7
4. http://edmi.parliament.uk/EDMi/EDMDetails.aspx?EDMID=30613%09%09%09%09%09%09%09&SESSION=875
5. http://thisisbristol.co.uk/displayNode.jsp?nodeId=144936&command=displayContent&sourceNode=144919&contentPK=16976765&moduleName=InternalSearch&formname=sidebarsearch
6. http://webbsteve.blogspot.com/2007/03/time-to-put-some-energy-into-power-from.html
7. http://www.publications.parliament.uk/pa/cm200203/cmhansrd/vo030204/halltext/30204h05.htm
8. http://thisisbristol.co.uk/displayNode.jsp?nodeId=144936&command=displayContent&sourceNode=144919&contentPK=17372301&moduleName=InternalSearch&formname=sidebarsearch
9. http://politics.guardian.co.uk/green/story/0,,1761552,00.html
10. http://edmi.parliament.uk/EDMi/EDMDetails.aspx?EDMID=33263
11. http://edmi.parliament.uk/EDMi/EDMDetails.aspx?EDMID=30352
12. http://www.n-somerset.gov.uk/cairo/docs/doc8174.htm
13. http://news.bbc.co.uk/1/hi/wales/5039918.stm
14. http://www.defra.gov.uk/corporate/ministers/speeches/ben-bradshaw/bb070316.htm
15. http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2007/05/21/nbrown221.xml
16. http://icwales.icnetwork.co.uk/0100news/0200wales/tm_headline=ministers-support-severn-barrage&method=full&objectid=19140299&siteid=50082-name_page.html
17. http://www.bristolgreenparty.org.uk/nr/060307severnbarrage.htm
18. http://www.glosgreenparty.org.uk/index.php?option=com_content&task=view&id=1807&Itemid=2
19. http://southwest.greenparty.org.uk/southwest_greens_support_tidal_power_in_severn_estuary
20. http://politics.guardian.co.uk/green/story/0,,1761552,00.html
21. http://politics.guardian.co.uk/green/story/0,,1761552,00.html
22. http://news.bbc.co.uk/1/hi/wales/4898514.stm
23. http://thisisbristol.co.uk/displayNode.jsp?nodeId=144936&command=displayContent&sourceNode=144919&contentPK=14355106&moduleName=InternalSearch&formname=sidebarsearch
24. http://www.wildlifetrust.org.uk/avon/wildlife/78-severn_estuary.htm
25. http://news.bbc.co.uk/1/hi/wales/6696915.stm
External links
★ Friends of the Earth "Tidal Lagoons" Plans
★
★ Independent report on "Tidal Lagoons" for the DTI and the Welsh Development Agency
★ BBC Gloucestershire background videos and information
★ Severn Lake Official Website
★ World Wildlife Fund "Turning the Tide"
★ Severn Tidal Power Group report for UK Government DTI
★
★ Appendices to - Severn Tidal Power Group report for UK Government DTI
★ Institute of Civil Engineers Severn Barrage environmental reappraisal
★ Estuary energy plan makes waves The Guardian 26th April 2006
★ Institute of Electronic Engineers Severn Barrage Tidal power appraisal
★ Memorandum by the Severn Tidal Power Group to Parliamentary Committee
★ Standing Conference on Severnside Local Authorities (SCOSLA)
★ Westminster Hall Debate on the Severn Barrage
★ Sustainable Development Commission project looking at 'Tidal Power in the UK'
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