The building and land costs of the Shannon tunnel will be €420 million, 18 per cent more than the original estimate, according to the National Roads Authority (NRA).
The authority has signed a deal with the Irish-led international consortium, Direct Route, worth €660 million. This figure covers maintenance and reinvestment in the project over 30 years as well as €420 million for building and land purchase.
When the then transport minister, Séamus Brennan, announced the project in 2004, he estimated the cost at €355 million. This covered building and land purchase, but not maintenance and renewal.
An authority spokesman said yesterday that Mr Brennan's estimate did not include maintenance and renewal, as it would not have been possible to project what these figures would have been. The spokesman explained that as private companies were bidding to build and operate the tunnel, Mr Brennan could not say how they would value the maintenance and reinvestment deal.
Direct Route will be entirely responsible for the tunnel for 30 years, and will charge a toll for using the road.
The company is expected to earn €456 million from tolling over that period.
This means that the tunnel will cost a total of €1.1 billion over 30 years.
The State will be the tunnel's ultimate owner.
Excluding the €420 million bill for building the tunnel, on the basis of the contract value and the estimates of tolling turnover, Direct Route can expect to generate €696 million over the 30-year period.
This represents an average turnover of €23.2 million a year.