Designs for the Qatar-Bahrain Causeway are being substantially revised after contractors realised the original gradient for the bridge would be too steep for trains to use the proposed rail link.

Revisions to the design are under way and contractors say the extra work required on the 45-kilometre-long causeway could add $1bn to the final cost, raising it to about $4bn.

First mooted in 1999, the bridge, known as the Friendship Causeway, was originally designed to allow ships up to 40 metres high to pass underneath in a 400-metre-wide shipping lane, but was only intended to comprise a dual carriageway crossing for road vehicles, which can handle steeper gradients, rather than a rail link.

“It has been decided to stop the old design,” one source close to the project tells MEED. “The road bridge was designed to have a 3 per cent gradient to reach the 40 metre clearance height for shipping, but trains can do 1.2 per cent maximum.”

In November 2008, the Qatar-Bahrain Causeway Foundation, which comprises members of both governments, decided to add a railway to the project that will link to Qatar’s national rail system and from there to the forthcoming GCC rail network, and offer passenger and freight services.

The rail link fundamentally alters the scope of the project. The designers must now soften the gradient to accommodate the railway. Such a major change has ramifications for the whole design.

“We will build two additional rail tracks at the side of the road bridge,” says the source. “This means that the concept for the foundations has to be quite different to how it was just for the road. For the road bridge we need a single pile, but with a rail bridge attached we need three piles in some places. We also have to increase the length of the bridge by 7km to allow the 400 metre span in the marine channel as well. And the whole design has to be much more rigid than it does for a road bridge alone.”

Work on the new design remains ongoing but contractors are not expecting major delays to the project. In May 2008, a consortium led by state-owned developer Qatari Diar and French contractor Vinci Construction Grand Projets won the construction contract to build the causeway. The group also includes Germany’s Hochtief, Athens-based Consolidated Contractors Company, Dredging International from Belgium, and the Qatari Middle East Dredging Company. Denmark’s Cowi is working as the design consultant on behalf of the consortium.

In December 2008, the foundation selected the US’ KBR and UK group Halcrow to provide programme management services on the project.

“The consortium and Cowi are still working on the new design,” says the source. “These are very significant changes to incorporate. Two more tracks, two more bridges and a longer bridge. It is a completely different animal.”

These alterations will inevitably have an impact on the final cost. The price tag for the previous road bridge design was estimated at about $3bn.

Sources close to the project say the addition of a rail link will push that up by about $1bn, although the cost of the extra work will be partially offset by the recent slump in raw materials prices.

“The increase in the cost has still not been defined, but I expect the cost could rise by about 30 per cent,” says the source.

“We will not know for sure until we have finalised the specifications. In particular, the cost will depend on the foundations and a decision on the type of train we are going to use.”

The Qatar-Bahrain Causeway Foundation was unavailable for comment, but the source says there have been “no complaints from the client” about the increased cost.

Despite the changes and the ongoing efforts on the new design, contractors on the project remain confident that early-stage work can begin in the coming months.

“We still expect preliminary work to begin this summer,” says the source. “We will begin with the marine works, but there is still much to be done, including a lot of environmental considerations to take into account.”

Once work begins in earnest, the foundation expects the Friendship Causeway to take about four years to build.

Unveiled a decade ago, it is one of the most ambitious projects planned for the Gulf. The project also symbolises the growing links between Manama and Doha since they resolved a territorial dispute over the Hawar islands in 2001 (MEED 9:5:08).

Doha is currently developing plans for its own rail network with rail service operator Deutsche Bahn. The railway would join a high-speed link from New Doha International airport through the centre of the capital.

The line across the bridge would also give Bahrain a connection to the GCC railway. That 1,500km project will run down the east coast of the Arabian peninsula, from Kuwait’s border with Iraq to the Omani port of Salalah.

Member states are expected to endorse the $14bn project in the summer.