CONTRACTORS EYEING the £156M design and build contract to construct the 4.6km road tunnel under Dublin Port are considering using tunnel boring machines on the project, despite the prospect of adding up to 20% to the cost of the job.
News that contractors might not use the controversial New Austrian Tunnelling Method for the central 2.6km bored section of the tunnel was revealed during the third week of the public inquiry into the scheme.
Under cross-examination, Dublin Corporation engineer Gerry Murphy said contractors had shown interest in using boring machines for the work during discussions at tender pre-qualification meetings.
But project engineer for Austrian tunnelling consultant Geoconsult Johannes Wageneder said earlier that using a TBM for the work would add 10% - 20% to the cost of the project.
Murphy also said the contract will be based on the traditional ICE form of contract with a slight variation that required the contractor to use separate design and checking engineers. This will be in addition to the client's own resident engineer, he said.
The Corporation insists the tunnel is essential to cater for a massive increase in city traffic. It also says that while the initial design and estimate have been carried out using NATM, the final decision will be left to the contractor.
Local residents have opposed the tunnel since it was first suggested in 1992. They fear the project, which has been costed by consultants Ove Arup and Geoconsult using NATM, cannot be built safely within the current £156M estimate.