Dublin Port Tunnel

Dublin Port Tunnel Construction, 2004

December 2006, southbound entrance

The Dublin Port Tunnel (Tollán Calafoirt Bhaile Átha Cliath in Irish) is a road traffic tunnel in Dublin, Ireland, that forms part of the M50 motorway. It is the second-longest urban motorway tunnel in Europe after Södra Länken in Stockholm, Sweden. . However by European standards, it would not be considered a long road tunnel, being dwarfed by many other European road tunnels such as the Lærdal Tunnel in Norway (24.5 km), the St Gotthard Road Tunnel in Switzerland (16.4 km), the Mont Blanc Tunnel in France (11.6 km) and the Westerschelde Tunnel in The Netherlands (6.6km).

The twin tunnels form a two-lane dual carriageway connecting Dublin Port, which lies to the east of central Dublin, and the M1 motorway close to Dublin Airport. The tunnels are 4.5 km (2.8 miles) in length and total project length of 5.6 km (3.5 miles). It had final cost of approximately €752 million. Their has been much discussion as to the wisdom of building the tunnel in the first place as the Port of Dublin may be relocated in the medium term.

The tunnel was officially opened on 20 December 2006 by Taoiseach Bertie Ahern, TD, however it was initially only open to HGVs. It was opened to all traffic on 28 January 2007.

Purpose

The tunnel relieves surface road congestion in Dublin city centre by diverting heavy goods vehicles (HGVs) from Dublin Port directly onto the motorway network. This has positive knock-on effects for bus users, pedestrians and cyclists travelling along the city quays, including better air quality and safer travel.

To discourage commuters from using the tunnel, vehicles other than HGVs are heavily tolled. HGVs travelling north and west benefit from the expected six minute journey time through the tunnel. A tunnel was chosen as it was decided that a surface relief road was not feasible.

The Dublin Bus Route 142 uses the tunnel to get to the port area of the city from the northern suburbs.

Longer distance buses from Belfast, Derry and Letterkenny occasionally use the route as an alternative to the heavily congested surface roads.

Port tunnel project

The tunnel was first suggested in the 1990s after a number of transportation and engineering studies and was included in the Dublin City Development Plan 1999 – 2005. The project was approved following a public inquiry in 1999.

The tunnel forms part of the National Development Plan and funds have been provided under this plan to the National Roads Authority by the Department of Transport. The contract is managed by Dublin City Council and supervised by Brown & Root, a unit of Halliburton. The main contractor is a Japanese-British-Irish consortium Nishimatsu Mowlem Irishenco¹ (NMI), appointed in 2000.

The tender price for construction of the tunnel was €450 million. The final project cost was brought to €752 million by land acquisition, design, insurance, legal and other services, plus supervision by Brown & Root.

Construction commenced in June 2001 and the tunnel was originally due to open in 2005 after an elapsed time of 43 months. Dublin City Council had confirmed (15 November 2006) that the Port Tunnel was to open on 20 December 2006, giving an elapsed time of 66 months.

One reason for the project extension was to allay residents’ noise concerns. Under some areas such as Griffith Avenue and the Cloisters, boring was restricted to 16 hours per day. Under Annadale Crescent it was reduced to 13 hours.

Tunnel specifications

Interior of the port tunnel

• Length: 4.5 km (2.8 miles) - total project 5.6 km (3.5 miles)
• Bores: 2
• Bore width: 11.77 m (37 ft)
• Lane width (two per bore): 3.65 m (11 ft)
• Shoulder width (two per bore): 1 m (3 ft)
• Bore height: 4.9 m (16 ft)
• Operating height: 4.65 m (15 ft)
• Lowest point: -30 m (-95 ft) at Marino

Tunnel design

The tunnel is built in five distinct sections: two “cut and cover” sections, two bored sections, one through open-clay and one through hard limestone and a specialised pipe-jacked section under the Dublin-Belfast railway line.

Cut and cover

The “cut and cover” sections at both ends featured excavations as deep as 12 m into which horseshoe-shaped sections of cast concrete were dropped and backfilled. The southern section, at Fairview, is 500 m long while the northern cut and cover channel from Whitehall Church to Shantalla extends over 1500 m. This work was undertaken by the Mowlem and Irishenco units of the consortium.

Tunnel boring

Both bored sections were initiated from a shaft 33 m deep and 57 m in diameter created at Collins Avenue by Mowlem in a joint venture with Intrafor of France. From here, the Tunnel Boring Machines (TBM), managed by Nishimatsu, were sent north through open clay and south through hard limestone. As is traditional, both machines were named after women – Meghan for 650 m of open clay and Grainne for 2,600 m of limestone.

TBM-1 “Grainne” headed south, passing under Griffith Avenue, Marino and Fairview. It was then dismantled, turned around and used to bore a second tunnel for the southbound carriageway. The machine, designed by Herrenknecht of Germany, was 156 m long, 12 m in diameter and was delivered to Dublin port in 105 parts carried by three ships, taking one week to unload. Combined, these bores resulted in the removal of 500,000 m³ of rock.

A similar process was followed northwards by the 60 m long TBM-2 “Meghan” boring from Collins Avenue to Whitehall Church, first creating the southbound carriageway.

The bores were completed with breakthrough into the reception shaft on 18 November 2003 and 18 August 2004 for clay and rock, respectively. Much of the bored sections are 21-23 m below the surface, with the lowest point at Marino, towards the southern end, a point that also hosts the tunnel's drainage sump.

Pipe jacking

A particular challenge was faced near the southern portals where the tunnel passes under the Dublin to Belfast railway, a line that also carries suburban and commuter services. The railway was constructed on an elevated embankment made up of soft materials resting on alluvial deposits of sand and silt. Because the railway had to remain operational at all times, the cut and cover approach could not be used. Nishimatsu constructed a pipe-jacked supporting structure for the railway 3.5 m below the surface. The tunnel was then constructed in the supported space using horse-shoe sections and backfilled.

This 60 m section took 24 months to complete and resulted in the adjoining Alfie Byrne road being raised by 1.5 m. It also resulted in one incident of subsidence that closed the railway for three hours. This closure cost the contractor €300,000 in penalties - €100,000 per hour.

Other works

A new entrance and exit for the Dublin port was constructed including a new bridge over the Tolka river that connects to the toll plaza and southern portals. A new junction and underpass facilitates traffic from the East Wall Road towards the tunnel.

Southbound traffic approaching the tunnel on the M1 can utilise two tunnel-bound lanes or two surface lanes that continue the M1 toward Whitehall. Traffic emerging at the southern portal approaches the toll plaza outside the port.

Tunnel operation

Following a tender process in 2005, the NRA selected Transroute International, part of France’s Groupe Egis, to operate the tunnel for a period of five years with an optional renewal of two years. The service contract provides for operation, maintenance, safety, traffic management and toll collection. A new subsidiary, Transroute Tunnel Operations Ireland Ltd, has been set-up for the purpose. Tunnel operations, including tolling, employ between 50 and 60 people. The service contract is worth €15 million to Transroute over the five-year period.

Elsewhere, Egis was also selected to provide a central system to enable interoperability between different electronic toll collection systems in Ireland.

Tolling

A toll plaza operates from the southern tunnel control building by Transroute who collects tolls from cars and light commercial vehicles, paid in cash or electronically. HGVs use a toll-free lane. A toll of €12 (peak) and €6 (off-peak) is levied on cars and light commercial vehicles. Peak is defined as 6am to 10am southbound and 4pm to 7pm northbound, except Saturdays, Sundays and public holidays. There is a reduced toll between 10pm and 6am of €3 which applies to all non-exempt vehicles travelling north or south. Tolls collected are remitted to the Department of Transport.

BGA Fleming award

The northern cut and cover tunnel was joint winner in 2004 with the World Trade Center Project of a geo-technical award for the earth retaining works on the M1 motorway. This prize awarded each year by the British geo-technical association.

Safety features

There are 15 pedestrian crossing points (PCPs) situated 250 m apart with emergency telephone and fire fighting niches. Additional fire hose reels are located 125 m from each niche. There are four vehicle crossover points at 1 km intervals comprising a lay-by plus emergency and recovery area. These are located under Shantalla, Collins Avenue (site of the original launch shaft), Marino and Cloisters.

GSM telephone and FM radio coverage is carried into the tunnel with break-in facilities over public broadcasts in the event of an emergency.

There are 420 cameras attached to the vehicle management system (VMS). A maximum speed limit of 80 km/h is in place and HGVs are prevented from using the outside lane.

Overheight vehicles are detected up to 3 km from the tunnel portals and automatic signage is then deployed to stop the vehicle. If necessary, barriers can be lowered to protect the portals.

Controversies

House damage

During the hard-rock boring works vibration caused some damage. Houses in the Marino area were surveyed before and after tunnelling and necessary repairs reimbursed. There were 241 claims and these were adjudicated by a loss adjuster. A fund €1.5 million was set aside.

City centre ban

Dublin City Council's policy was to introduce a ban on trucks in the city centre between 7am and 7pm, but it agreed to delay this ban for a period of two months until 19 February 2007. This was because of opposition from the Irish Business and Employers Confederation (IBEC), the Irish Road Haulage Association and the Dublin Port Company. The hauliers cite unreasonable traffic congestion on the M50, especially during the imminent widening of the northern section while IBEC and the Port Company are concerned about restrictions on free movement of goods.

The Sunday Independent ran a story on 12 November 2006 revealing the ban that came into force soon after as the Tunnel opened. Taoiseach Bertie Ahern reportedly put pressure on the Council to abandon their phased approach and initiate the ban in one go. The plan has been criticised by opposition parties who said such a move would simply dump the problem on to an already "dangerously crowded M50".

East link tolls

One company located south of the Liffey, Marine Terminals Ltd, considered taking legal action against the Council if it went ahead with banning trucks from the city. This was because a ban would force the company to use the tunnel, which would mean crossing the privately owned and operated East-link toll bridge, incurring a €4.80 charge each way. In response, the council agreed with National Toll Roads (NTR), the operator of the bridge, to lift the toll for trucks.

Height controversy

Even before the commencement of construction, the tunnel was criticised for not being high enough. Critics argued that it would not be able to accommodate heavy goods vehicles higher than 4.65 m (15 ft) and that it should be built with an operating height of 5.5 m to accommodate virtually all sizes of trucks. Proponents of the chosen design argued that it made best economic sense and that it would be able to accommodate most heavy vehicles with only a minor percentage having to use the surface road network. Construction went ahead as planned, but speaking at the breakthrough ceremony, Jimmy Quinn of the Irish Road Haulage Association stated that a future generation may look back and say (about the tunnel not being high enough for very high trucks): "Maybe they should have done it when they were building it."

Water leaks

In Spring 2006, media reports revealed that the tunnel was leaking substantial amounts of water. This was as a result of sub-standard concrete being poured. When the concrete was removed during remedial works, protective membranes were punctured, resulting in leaks. Once the membranes and concrete were re-instated, the leaks ceased.

Cost overruns

While it is often claimed that the project is over-budget, this is not actually the case. The tender price at €450 million is for construction only while the total project cost is approximately €752 million.

In September 2005, it was reported that NMI was launching a claim for an additional €300 million . The Council has stated that this claim will not be met and that the total project cost remains at €752 million.

Exit positioning

The Irish Road Haulage Association has pointed to the problem facing drivers exiting the northbound tunnel. Recent changes in road traffic regulations prevent trucks and lorries from using the overtaking lane of motorways. As the tunnel exits in the "middle" of the M1 motorway, drivers therefore have to immediately cross two lanes of traffic to get into the correct driving lane. This is also the lane that trucks and lorries need to cross to in order to turn onto the M50. See: image. They will have just 1km of road to make this maneouvre.

On the day the tunnel opened, it was revealed that the National Roads Authority have drawn up "secret" contingency plans which will be put into effect if it appears that the current configuration does not work out .

Relocation of Dublin Port

In October 2006, as the tunnel neared completion, the Progressive Democrats held a conference on their proposal to relocate Dublin Port to Bremore on the outskirts of Balbriggan, and to redevelop the port area for mixed high density uses. The Taoiseach, Bertie Ahern, has indicated his support for this proposal. .

Trivia

• On 10 December 2006 the Dublin Port Company and Clonliffe Harriers, a Dublin athletics club, staged a 10 km road race through the tunnel before its official opening.
• Mobile phones do work throughout the lenght of the tunnel.

Footnote

¹ Following bankruptcy, the name and assets of this eponymous and long-standing Irish company were bought by Mowlem before construction of the tunnel began. Today, Irishenco is possibly best described as an Irish-based branch of Mowlem.

References

• Dublin Port Tunnel Information Notes issued by DCC
• Groupe Egis Press Release

External links

• Dublin port tunnel official website
• Department of transport website
• RTE News short report on the breakthrough
• RTE News report on the breakthrough (Real video)
• Nishimatsu website on the Dublin Port Tunnel
• Mowlem
• Herrenknecht AG — makers of the tunnel boring machine(s) used.
• Groupe Egis — tunnel operators.