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Your questions answered: Thames Estuary Airport

Our expert panel answers your questions on plans to build a Thames estuary airport. Stephen Harris reports

Thames Estuary airport is back on the agenda, thanks to opposition to expanding Heathrow and enthusiasm from the mayor of London, Boris Johnson. As the government’s Airports Commission considers the best way of expanding the UK’s air travel capacity (although they’re mainly looking at south-east England), we put your questions to two of the
teams who have put forward proposals for a new hub in the Thames Estuary.

• The Thames Reach Airport consortium has been working for more than 10 years on plans for a privately funded £29bn two-to-four-runway airport on reclaimed land on the Hoo peninsular that would also include the Metrotidal project to build a tunnel under the estuary providing new road and rail loops, flood defences and tidal energy generation.

• Architecture firm Foster + Partners has proposed building a privately funded £24bn four-runway ‘Thames Hub’ airport on a raised platform on the Isle of Grain in the model of its artificial island airport in Hong Kong, linked to London via several rail lines, including HS1 and Crossrail.

Why would a Thames Estuary airport be preferable to expanding our existing infrastructure at Heathrow, Gatwick and/or Stansted, given the considerable extra costs involved and the extra time it will add to passengers’ journeys?

Foster + Partners: For many passengers using high-speed rail, a Thames Estuary airport could be reached in less time than it currently takes to get to Heathrow and the £24bn cost of a brand-new airport is less than two new runways at Heathrow. [Heathrow estimates building a third runway would cost £14bn–£18bn, of which £4bn–£6bn might come from government. A fourth runway would cost a further £8bn–£14bn.] Passengers would be able to take a direct train from St Pancras to the new airport in approximately 26 minutes using HS1; and journey times for passengers from Birmingham or Manchester would be drastically reduced. Heathrow requires major surface access improvements in an already congested area. Gatwick is as far, and Stansted further, than Thames Hub and they would both require substantial surface access improvements.

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Foster + Partners’ proposed Thames Hub airport, showing transport links

There are many other advantages to a four-runway Thames Estuary airport, not least the opportunity to relieve five million Londoners of the noise, pollution and dangers of flight paths over the capital. Without the constraints of an urban site, the airport would be more cost-effective to build and, unlike Heathrow, it can operate 24 hours a day, due to the sparsely populated area. It can open with capacity for 110 million passengers per annum within 16 years — the same timeframe as a third Heathrow runway, which would be full within a decade of opening. The proposed site is also strategically located close to the south-east’s major ports to enable the successful economic integration of rail, sea and air freight.

Thames Reach: Thames Reach Airport with the surface access provided by Metrotidal Tunnel will have a much larger catchment area and better connectivity for lower cost than expanding Heathrow, Stansted or Gatwick. The longer travel distance from northwest and west of London to the estuary location is more than made up by the more efficient travel time airside and landside when passing through the purpose-designed, new-build airport. Despite the billions proposed to expand and improve the capacity at Heathrow, the dispersed arrangement of gates between widely separated main terminals and two runway infields results in an inefficient airport configuration with higher travels times. Even with a modern mass-transit people-mover, a distance of up to 7.8km between train and satellite will result in substantially longer average transit times than a purpose-designed system.

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Artist’s impression of an airliner on final approach to Thames Reach airport

At Thames Reach Airport, with the airport station directly beneath and beside the airport terminals, a maximum of 2.7km from station to satellite on a single passenger transit axis and a compact airfield with offset runways, there are savings of 30 minutes on average when passing through the airport system landside and airside, resulting in a 10-minute comparative proximity benefit. If the route for HS2 did not go out of its way to help Heathrow, the benefit of Thames Reach Airport would be even better. With a site to the east of London close to HS1, the comparative proximity of Thames Reach Airport is also much better than Heathrow for all areas northeast, east and south from Central London, including northern Europe as far as Paris, Brussels and Amsterdam.

Why combine the airport with the Metrotidal Tunnel project when this will increase the costs even further?

TR: Metrotidal Tunnel, integrated with new flood defences and tidal power, is funded independently by the private sector and these costs do not fall on the aviation agenda. So, contrary to increasing the aviation costs, Metrotidal Tunnel substantially reduces the residual cost of the new hub airport, enabling it to be funded by the aviation market and private sector. Metrotidal Tunnel also provides the necessary surface access improvements for both passengers and employees, including shorter routes from Cambridge, Ipswich and Gatwick/Crawley that avoid inner-London congestion so these areas will all be within the one-hour catchment using conventional rail services. The stopping service on an extended Crossrail and express rail services to St Pancras and Waterloo would also extend the one-hour catchment to surrounding areas of London and the West End.

What would be the biggest engineering challenges involved in the project and how do you intend to overcome these?

FP:Although it is a large project, it is relatively straightforward in engineering terms. The construction of the airport platform would use well-established civil engineering technologies, which have been used to build major airports on reclaimed land elsewhere in the world, such as Chek Lap Kok airport in Hong Kong. In Europe, similar reclaimed land techniques have been used extensively in Holland for many decades.

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The train station below Foster + Partners’ proposed airport

TR:The biggest civil engineering challenges are: the construction of the Metrotidal pool impoundment and weirs so that they are environmentally and hydrodynamically neutral for the Thames tideway while providing maximum flood-storage capacity and tidal pumped-storage output; and the subsequent timely construction of the airport platform within the pools. The configuration for the pool impoundment and weirs will be tested and refined on numeric models of the Thames tideway. This will optimise the flood-defence benefits during storm surges, while managing flow rates and sedimentation during normal tidal cycles, and provide a stable self-scouring system that requires no more maintenance dredging than at present.

Why have you chosen the site your plans are based on? Why has the 1970s plan to build at Maplin Sands not been pursued?

FP:The 2003 South East and East of England Regional Air Services Study (SERAS) study supplanted the work done on Maplin Sands and showed an inner-estuary location as the optimal site. We refined this work and settled on a proposal to the west of Maplin and to the east of Cliffe, where the impact on people and wildlife habitats could be minimised. Maplin still has a large amount of unexploded ordnance, the north of the Thames is more heavily populated and it is further away in terms of surface access. The Isle of Grain also emerged as the best location in the mayor of London’s recent assessment of 16 different airport sites in the south east.

TR:For the Metrotidal integration, the volume of a flood-storage system would have to be very much larger at Maplin to provide the same reduction of flood risk upstream. Similarly, the pools for a tidal power plant at Maplin, with a lower tidal range, would have to be very much larger to provide the same output. As a result the flood-storage and tidal-power functions would not be viable. For Maplin to provide benefits for the Thames Estuary region, the road and rail umbilical to the airport would need to loop back under the estuary to the Isle of Grain. Not only would this tunnel be more than twice as long but the associated road and rail orbitals around the estuary would be very much longer, which together trebles the construction costs of the airport surface access and creates longer journey times while significantly reducing the wider benefits.

How would the airport impact on tidal defences and flood risk and what measures do your plans include to mitigate against this?

FP: The airport itself does not change the nature of wider flood risks, but the development is an opportunity to integrate future flood protection with a wider infrastructure strategy. The Thames Estuary 2100 report from the Environment Agency looks closely at the impact on flood defences and habitat loss in the light of thermal expansion in the oceans and storm severity. This validates earlier work that we based our designs on to found the base level for the airport platform 7m above sea level, negating any flood risk.

TR: Metrotidal Tunnel is designed to provide the next generation of London’s flood defences without requiring a permanent barrier across the shipping channel, by using the controlled flood-storage capacity of the pools. The pools would provide a throttle for storm surges and a reduction in tidal squeeze (loss of intertidal areas due to rising sea levels) upstream while not throttling the tideway in normal tidal cycles, and provide tidal-pumped-storage renewable energy output to offset transport energy demands. They would also reduce the cost of the tunnel by increasing the proportion of cut-and-cover areas protected from the tides during construction, and create a balance of materials on site for raising the airport platform, while minimising the embodied energy and carbon audit of the platform construction.

How much of a threat is the sunken US warship SS Richard Montgomery that lies in the estuary and still contains around 1,400 tonnes of explosives, and what measures would you include to protect against the potential tsunami that may occur if the explosives were detonated?

FP:As the ship is close to one of Europe’s busiest shipping lanes, it is already closely monitored by the Maritime and Coastguard Agency — its latest report stated that the hull is reasonably stable, but the explosives are degrading. We believe there will come a point when the risks in doing nothing are greater than the risks involved in a carefully planned intervention, irrespective of whether or not the airport is built. At this stage, we are proposing further government-led studies to determine the future of the ship.

TR:The SS Richard Montgomery falls well outside the Metrotidal Tunnel and Thames Reach Airport impoundment. However, the risk of explosion should not be allowed to influence such an important infrastructure decision for the UK so there is a case for the Environment Agency to tender solutions and resolve the matter now. Solutions include raising a blast levee by pumping sediment around the north, west and south sides of the wreck and laying time-co-ordinated directional explosive charges to direct blast and associated waves towards the outer estuary. The Metrotidal pool impoundment would protect the airport from residual wave propagation westwards.

What specific measures would you take to replace the environments for internationally important breeding and migratory marine and bird species that will be lost during construction, and to where will the species be displaced?

FP:These natural habitats are already under threat from rising sea levels and storm surges yet there is limited funding available to protect them. An airport could be a catalyst for conservation initiatives, not only to mitigate the impacts of the airport development but to address wider habitat loss. Existing schemes, such as Wallasea Island have shown that estuary birds will readily use newly created habitats, so long as conditions are suitable.

TR: The loss of intertidal area within the pools is offset by intertidal areas upstream that will be protected from tidal squeeze by the tunnel and airport system. Similarly the area of low-lying freshwater meadows and creeks within the pools is offset by the substantial freshwater habitat area upstream that will benefit from improved flood protection. There are two strategies for providing replacement intertidal area and low-lying land. The first is to determine sites where managed retreat would be an economical solution to provide new designated intertidal areas without loss of existing sites. The second is to research sites in the outer estuary away from the airport platform where a stable new island habitat surrounded by intertidal areas can be formed by raising an impoundment on or beside existing shallows using tidal pumped-storage energy from the London Array.

One reader raised the prospect of installing nearby photobioreactors to capture carbon emissions from the airport that produce algae for sale as fishmeal. Do you think it would be worth pursuing this idea and how easily could it be done?

TR:Prevailing winds indicate that the carbon emissions and associated NOX contours will mostly fall over the open estuary to the northeast of the airport platform, where they will be rapidly dispersed by the winds and tides. If analysis can demonstrate a significant proportion of the carbon emissions can be captured in this area, there may be a case for exploring use of photo-bioreactors although concerns will arise from the associated capture of pollutants that would otherwise be dispersed. This area may also be suitable for the generation of energy from tidal-stream devices to compliment the predominant and more secure tidal-head output from the pools. Other wind directions will direct the airport emissions over the pools where for similar reasons there may be a case to explore the use of photo-bioreactors, with similar limitations.


Readers' comments (17)

  • Did not answer the increased flood risk associated with development upon the river Thames natural marsh flood defences adding that no reference was made to the coastal squeeze effect that this development would cause...a very unsatisfactory response.

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  • Something that I have not seen discussed in any detail is the changes that would be required to the UK's already extremely busy airspace.

    Heathrow, along with the other airports mentioned are already very well protected by large areas of controlled airspace monitored and controlled by a network of controllers.

    The addition of a new major hub airport would require the implementation of further controlled airspace in the South East, which would not only be expensive to set up and run but would also place further restrictions in the area effectively crippling General Aviation is the South East.

    Although not against the plan as a whole, it is time the CAA looked closely at rationalising controlled airspace to ensure space is maintained for all users and is not purely in place just to support commercial traffic. Should this go ahead, and I hope it does, I hope some middle ground can be found to make it beneficial for all of aviation.

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  • The 10,353 bombs estimated to be left inside the Montgomery after 50% were removed during the war in 1944, have always been safe to remove and yet the Department of Transport who have managerial responsibility for this wreck for the last 30 years since 1983 have never employed a single expert in the many fields of explosives expertise to even understand the managerial problems associated the technical aspects of this danger to the public.

    It is being even more irresponsible. They have sought legal advice on the many criminal laws that protect people from explosives that they have broken.

    Nor did they raise any concerns at the building of Europe's largest storage of liquid natural gas on the Isle of Grain, the proposed location of Boris Johnson's latest scatterbrain idea.

    I offered to have the risks associated with the wreck computer modelled in 2007 that was refused and found later that in 1997 the MoD establishment DERA , that I spent my career at under its former names of DRA and RARDE, also in their report that was commissioned by the DFT that the bombs were safe to remove and that they might be able to have the risks computer modeled with a view to define a safe zone, that is required by law to makes sure people are safe while decisions are taken on how to remove the risk.

    The current situation is that if the wreck did explode from a collision, capsize, movement of the cargo or it breaking up that have been stated as reasons why the DFT. It would completely demolish the surface silos holding the gas on the Isle of grain which when vaporise and mixed with four times its mass of oxygen from the air would produce the explosive power of 156 Hiroshima nuclear bombs that would kill all of us in the south-east of England including her Majesty and possibly many millions in France, dependent upon meteorological and prevailing wind conditions extant at the time

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  • @Mike Baker.
    Hmm! Terrorists are now acquiring scuba gear and underwater demolitions training?

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  • Mike Barker, I've told you a million times not to exaggerate.

    If I remember correctly, the Hiroshima bomb was about 15kton.

    Even if we assume that the calorific value of LPG plus the appropriate quantity of Oxygen was the same as dynamite,this would imply that there is half a million tons of LPG on the Isle of Grain. This seems unlikely, not to mention the fact that rather than exploding in a few microseconds it would take days or weeks to burn.

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  • I originally asked about the environmental impacts. The responses do not answer the question.

    FP Suggest the vast and unique estuary habitats can be recreated elsewhere or alternative habitats created. That is factually correct, but it wouldn't be where it's needed in the Thames Estuary, so you'd condemn species to history.

    TR suggests fragmenting habitats and further meddling with the estuary by engineering a new built-up habitat. This completely ignores the fact that the estuary is a busy shipping lane with complex inter-tidal flows that is prone to flooding and coastal squeeze.

    May I also draw your attention to the recent announcement from Sir Howard Davies, chair of the Airports Commission, stating that any environmentally damaging proposal will not be included in his interim report due out in December, and certainly won't feature in his final recommendation due in 2015.

    A Thames Estuary Airport is the most environmentally damaging of the 48 proposals submitted to Sir Howard.

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  • We need to start to relocate these species now and implement a new nature protected zone away from the new airport.

    We should not wait another 3 years until they decide to build an airport. If we want environmental habitats to exist in this country we need to be proactive with the governments ambitions and appeal for funding to trial and implement such rehoming projects. The government would then consider reclaiming areas for nature and Capturing land spaces to recreate examples where we can show any signs of a success story.

    The airport is just one modification planned for this area, what about the new crossing, London sea ports, tidal defence systems and hydro energy plants in planning? These will ultimately change the current tidal path and swaying water currents will destroy the marshes in decades? We should take this last opportunity to work with reason before we risk endangering wildlife or humans, just to say "I told you so!"

    With issues such as population growth and concerns over wider environmental issues caused by Heathrow, Gatwick and Stansted a new airport is the best choice. The Thames estuary airport even combines the option of international rail which heavily reduces the number of flights taken each year. The argument should be about it's design that will be more environmentally friendly than Heathrow now and certainly in the future.

    Environmental concerns cover a wide scope of issues including air pollution, noise pollution and then pollution to the local and wider environments.

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  • Why not use aircraft that can land on both water & land. No airport required. Just land on the Thames instead. All you would need is a landing & boarding area. This would be very cheap and more convenient!

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  • How cheap would it be to replace the world's passenger aircraft fleet with seaplanes?

  • I have no idea who Peter Higgins is but in fact the Hiroshima bomb had an estimated yield equivalent of 16 K tons of TNT, as can be seen in Wikipedia.

    We are not talking about the LNG burning but exploding when mixed with four times its mass of oxygen in the air, as happens when LPG is used to power vehicle engines that Mr Higgins may have heard about.

    LNG has a density just under half of water and the chemistry is easy for its complete combustion but the oxygen depleted atmosphere would lead to other products being formed in addition to carbon dioxide that would notably be the very poisonous carbon monoxide adding to the lethality of the gas cloud.

    Methane reacts with oxygen in the ratio of 1:4 for carbon dioxide to be formed which is a simplistic overview because the metrological and prevailing winds, if present, would alter the mixes of carbon products formed but the total mass of the one million m3 of LNG stored on the Isle of Grain does equate to 156 x 16 K tons of TNT equivalent as I stated.

    This can be seen in the National Grid Brochure reassuring LNG is so safe it cannot burn without oxygen that is true but they are economic with the facts when mixed with four times its mass of oxygen, it actually becomes an explosive gaseous mix that powers vehicles to run on LPG methane and propane.

    It is reassuring there is a strict speed limit of 15 mph on the site and a smoking ban.

    I am not too sure if any ban on vehicle exhausts is in place but when other countries who store their LNG in disused mines or insist such silos were buried, are ignored I get concerned.

    In the case of the Montgomery exploding, buried silos would not lead to the gas being vaporized to explode but a likely ignition of the damaged super structure on the site that might lead to fires that may be possible to extinguish or burn out with little chance of a significant explosion.

    Other countries insist on their supplies being piped in underground pipes because there has been no test carried out to determine the likely events of a collision or sinking of these massive super tanker vessels that hold a quarter of the total supply on the Isle of Grain and would have an equivalent of 39 Hiroshima bombs.

    The concern of LNG being a terrorist option was raised by Cindy Hurst in her paper. Google Terrorist Threat to Liquefied Natural Gas. Fact or Fiction

    There is no World LNG Authority to advise on the safest means of its transport and storage but the UK have chosen the worst of the options and located it in the worst possible place within the danger zone of the Montgomery exploding.

    This makes it the world’s largest IED with more explosive than all the explosives laid by all the terrorists in the world conveniently in one place.

    The HSE carried out a risk assessment before the first silos were built in 1982 and failed to mention the Montgomery close by.

    OFGEN has responsibility of importing our energy requirements but kept quiet also but if the DfT had any explosives experts employed, they would have certainly raised the concerns that I am doing now.

    A ten tonne boiler section landed on the Isle of grain See Princess Irene on Wikipedia.

    No need for a scuba course.

    A jet ski packed with explosives would do Morkullen!

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  • It would be a lot cheaper than the airports or extra runways spoken about in this article & not take up any more land space. Plus it would not have to be done all at once. It may also be possible to adapt present aircraft to this idea.

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