The Austrian engineering firm convicted in London yesterday of safety failures over a tunnel collapse at Heathrow Airport in 1994 is involved in designing the £180 million Dublin Port Tunnel project.
Geoconsult, dubbed in court as the "watchdogs who didn't bark", was fined £500,000 sterling for its role in the collapse of part of a tunnel for the Heathrow Express rail link. It was "one of the worst civil engineering disasters in the UK in the last quarter of a century".
The firm had pioneered the New Austrian Tunnelling Method (NATM), which involves spraying each section of a newly-excavated tunnel with concrete to form a retaining shell. Conventional tunnelling relies on building a concrete structure to retain a tunnel as it is bored. Geoconsult's involvement in Dublin dates back to 1992, when the firm was engaged by Ove Arup and Partners, consulting engineers, to advise on tunnelling options for the proposed Eastern Bypass motorway. It recommended the use of NATM, partly because it is cheaper.
Subsequently, after the Eastern Bypass had been officially shelved (at least temporarily), Ove Arup and Geoconsult formed a consortium for a successful bid to design the Dublin Port Access Route, conceived largely as a tunnel between the M1 at Santry and the north port area.
Again, NATM was to be the preferred tunnelling technique, though Dublin Corporation's project team - acting on behalf of the National Roads Authority - has emphasised that other options could be put forward by civil engineering contractors at tender stage.
Geoconsult was embarrassed by a British Health and Safety Executive report on the Heathrow collapse, which queried the use of NATM.
But it pointed out that the Dublin Port Tunnel would be cutting through hard limestone rather than soft boulder clay for much of its length
The HSE report made 97 recommendations covering legislation, risk management, organisation, control, communication, competence, planning, design, monitoring and construction of NATM tunnels - a list so onerous that it could eliminate the method's competitive edge.
The report noted that closely-juxtaposed tunnels - such as the twin-bore envisaged for Dublin - required "particular review". They would also have to be "robust" and based on a thorough ground investigation to minimise the risk of running into unexpected conditions.
Balfour Beatty, fined £1.2 million as main contractors for the Heathrow rail link, was running a self-certification system which gave it control of construction and design. Only one Geoconsult engineer was employed to monitor soil shifts and interpret any data.
It is anticipated that the Dublin Port Tunnel will be put out to tender as a "design and build" project.
However, the project team has been at pains to stress that it would be properly designed and that detailed day-to-day monitoring would ensure the required level of safety.
Two major changes have already been made in the design of the project. Its depth running underneath some 300 houses in the Marino area of the city has been significantly increased while the tunnel's northern portals are relocated from Whitehall to Santry. These changes have increased the cost by some £30 million, bringing the latest estimate to £180 million.
There is general agreement that the port tunnel will cost considerably more by the time it is finally finished in 2003 - at least two years behind the original schedule. Many residents of Marino remain firmly opposed to the scheme, especially those living in houses above the proposed tunnel alignment. They will join other opponents from Santry and East Wall in making their case at the public inquiry, due to start by the end of March.
