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Auld Reekie's hot tattie

Edinburgh rail link - Construction of new rail links to Edinburgh Airport have become a political hot potato. Andrew Mylius finds out what is planned.

Edinburgh Airport Rail Link (EARL) will have a reach far greater than its 14km length would suggest possible.

'You are connecting not just Edinburgh to the airport, but places as far away as Newcastle and Carlisle. By the time the rail link's complete the airport will have a huge catchment of 3M people, ' says Scott Wilson project director Gordon Crighton.

Scott Wilson is lead designer for the £610M EARL scheme, which was approved by the Scottish Parliament in March, but which is being fiercely opposed by the Scottish National Party (SNP) in its campaigning ahead of next week's Scottish elections (see box).

Promoter and client Transport Initiatives Edinburgh is an agency created by the Scottish Executive and owned by Edinburgh City Council. It started with a study of which towns and cities would most benefit from connection to Edinburgh Airport.

Consultant SKM produced a report in spring 2003 setting out options of a spur from Edinburgh to the airport with suggested links to Glasgow, Stirling and Dunblane, or to Fife, Aberdeen and Inverness.

NCE spoke to Crighton and Scott Wilson senior project manager Gail Jeffrey in February.

'In May 2003 there was a ministerial statement saying that connections would be made to both Glasgow and Fife, ' says Jeffrey. 'We were appointed to give technical and environmental advice and asked to develop the scheme to the point where the client could submit a private bill to build the railway.' It quickly became clear that, as well as giving access to the airport from across a wide geographical region, the airport would become a transport nexus, easing journeys across the region.

Last year a private bill was presented to the Scottish Parliament. It was approved in March this year and gained Royal Assent this month. Only the possibility of a Scottish Nationalist Party victory in the 3 May elections stands in the way.

'Preparation has been going ahead assuming that Assent will be granted, ' Jeffrey says.

'Designs and specications will be sufciently detailed to put out to tender. We aim to start construction next year and want to get on site with utility diversions and advance works this year.' All going to plan, the rail link will open in 2011.

Creating the rail link will involve construction of four new junctions and one junction upgrade. The new junctions will enable trains to split from existing intercity routes - 'we're not going to be running extra services; we'll be diverting eight to 10 trains per hour on the existing timetable via the airport', Jeffrey says.

The junction upgrade is needed at Winchborough on the Edinburgh-Glasgow Line, south west of the airport. 'It's a 50mph line at the moment and we aim to put the line speed up to 100mph, ' Jeffrey says.

Right in the middle of the EARL will be 1.8km of 6m diameter twin-bore and cut-and-cover tunnel, carrying the railway under Edinburgh Airport's runway.

'The tunnels are without doubt the project's biggest technical challenge and hold the biggest risk, ' says Crighton. 'They'll be driven with a tunnel boring machine (TBM), but cover is small - it's 6m - and the ground difcult. It's a mix of boulder clay with sand lenses and a high water table.' Tunnels will pass under the River Almond, which is prone to ooding.

Owner of Edinburgh Airport, BAA, has experience of tunnelling under taxiways at Heathrow as part of its Terminal 5 works.

'With runways no deection at the surface is allowed so we will need to carry out ground treatment prior to tunnelling, ' says Crighton.

He anticipates sinking shafts either side of the runway and injecting grout. 'The whole runway will be instrumented - we'll start putting that in this year. The tunnel has to be built without stopping air traffic so we'll be monitoring movement of millimetres, not inches.' As important as preventing settlement during excavation is guarding against heave during ground treatment. 'You need to make sure you are not pushing the runway up while you're injecting grout. We have a experienced stakeholder in BAA, but what this project needs is the best tunnelling contractors in the world, and a high-quality earth pressure balance TBM'.

Halcrow and Donaldson are carrying out tunnelling design and ground investigation, with Scott Wilson supervising and carrying out railway design, environmental compliance, safety management, quality, risk, and cost-management work, as well as procurement support, and stakeholder liaison.

While the rest of the engineering is 'conventional' there are challenges, Crighton notes. The lines will run across farm land, but the scheme has faced some fierce objections.

Disruption to the existing railway will be limited by keeping work to brief three to four-day 'long-weekend' possessions so design effort is being put into developing junctions that can be built entirely off-line and slid swiftly into place.

The airport's station will be designed for nine car trains.

'Most trains at the moment have six cars, ' Jeffrey says. But platforms at Edinburgh Waverley Station are being upgraded for eight-car trains. 'We're allowing for growth of capacity, ' he says.

Who's who

Client:

Transport Initiatives Edinburgh/ Transport Scotland Lead consultant:

Scott Wilson Tunnel designer:

Halcrow Ground investigation:

Donaldson Architect:

Aedas Environmental consultant:

ERM Cost and quality consultant:

Turner & Townsend

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