THE closeness of houses to the Dublin Port Tunnel would make the controversial New Austrian Tunnelling Method (NATM) proposed for its construction "highly questionable", according to an independent assessment of the environmental impact study of the scheme.
The assessment of the £130 million project, carried out in the School of Engineering at Trinity College, Dublin, warns that further hydrogeological work is needed to determine the effects of using shot blasting to bore the twin tunnel through hard limestone under more than 270 houses in Marino.
Though the EIS insisted that full adherence to the relevant British Standard would prevent damage to buildings, the TCD assessment says shotblasting would "take place simultaneously with draw down effects on the water table" and this could cause structural damage.
It notes that a design and build contract is recommended, with the tunnelling technique to be specified by the contractor. "If NATM is to be used, the contractor will be responsible for adherence to a safety code which has yet to be developed," says the report's author.
"It is not clear to me that this code can be left to the discretion of the contractor and yet the client (the National Roads Authority) may not wish to be involved".
In fact, I personally believe that the closeness of property to the tunnel would make the NATM method highly questionable."
While the predictions in the EIS were based on science engineering, the assessments residual effects were "subjective", the report says. "In particular, I disagree with the conclusion that the long term effects on property values in the vicinity of the tunnel will be negligible."
The TCD report suggests the EIS authors "seriously underestimate" the resistance of house holders. They also implied monitoring would only be necessary for the construction phase, whereas it would "need to continue for several years".
It queries a lack of detail in the EIS on ventilation requirements for the tunnel and on the proportion of port traffic which would be unable to use it - such as car transporters - as well as whether the permanent provision of a heavy breakdown tow vehicle, to deal with emergencies, had been costed.
Though the EIS was "competently presented and demonstrates great care in its detailing", the £130 million budget had not been subjected to cost over run analysis. "A cost over run or bids (from contractors) in excess of £130 million should he anticipated," the TCD assessment says.
And while the decision to build the planned dual carriageway route was now almost a fait accompli, the £130 million cost had been justified by the "extensive use of the tunnel by cars" - and not just the port related traffic it was intended for.
"This goes against the current perceived wisdom that the basis of future transportation planning should be to squeeze people out of cars and onto public transport," the study says.
