IARNROD Eireann will seek planning permission early next year to build an underground DART line in Dublin costing up to €3bn.
The proposed new line would run from the Docklands to Inchicore. Capacity would be 20 trains in each direction per hour, potentially allowing 64,000 commuters to use the line every 60 minutes.
The completed line would connect the Northern and Kildare rail lines and link all rail systems -- DART, commuter, intercity, Luas and Metro North -- into an integrated and cohesive network.
The rail operator intends to seek planning permission in the New Year to build the 7.5km line under Dublin city, which would be financed under a public-private partnership (PPP) model.
This means the private sector would build the line and receive annual payments over a concessionary period -- generally up to 20 years -- from the railway company to pay off construction costs.
Despite the economic downturn, the Government has told both Iarnrod Eireann and the Railway Procurement Agency -- which is planning the €3.7bn Metro North link from the city centre to Swords -- to continue designing the projects and secure planning permission so they are ready to go.
Transport Minister Noel Dempsey has said both projects are priorities. However, a decision on funding will not be made until planning permission is granted.
Iarnrod Eireann says the underground DART is the "single-most important piece of infrastructure" to ensure a shift from private to public transport.
It said all options in relation to the PPP were being considered, including the length of time over which the project cost would be repaid.
"All options are being explored in relation to PPP including the concessionary period and the type of contract," a spokesman said.
"The Government has stated to us it is our number one priority for infrastructure and we are proceeding on that basis."
Five of the six stations on the 7.5km line would be constructed below ground, with an overground station at Inchicore.
The planned underground stations are located at Heuston, Christchurch, St Stephen's Green, Pearse Street and Docklands, and all are being designed to cater for a capacity of 60,000 people an hour to facilitate the future growth of the capital's transport service.
The company said the station entrances are being designed as "distinctive identifiable landmark structures", and that natural lighting would be used where possible.
The underground stations would be constructed using underground mining techniques that would minimise the effect on local residents.
Two tunnels, each containing a single track, would be excavated using Tunnel Boring Machines (TBMs).
Each tunnel would have an average depth of 24 metres, over 80 feet, below ground level.
If the project gets the go-ahead, between 6,000 and 7,000 jobs in each year of the construction phase would be created.
Work would begin in 2011 and should be completed by 2016.