Jack Lynch Tunnel
The Jack Lynch Tunnel is an immersed tube tunnel and an integral part of the N25 southern ring road
Ring road
A ring road, orbital motorway, beltway, circumferential highway, or loop highway is a road that encircles a town or city...

 of Cork
Cork (city)
Cork is the second largest city in the Republic of Ireland and the island of Ireland's third most populous city. It is the principal city and administrative centre of County Cork and the largest city in the province of Munster. Cork has a population of 119,418, while the addition of the suburban...

 in Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

. It is named after former Taoiseach
The Taoiseach is the head of government or prime minister of Ireland. The Taoiseach is appointed by the President upon the nomination of Dáil Éireann, the lower house of the Oireachtas , and must, in order to remain in office, retain the support of a majority in the Dáil.The current Taoiseach is...

, Jack Lynch
Jack Lynch
John Mary "Jack" Lynch was the Taoiseach of Ireland, serving two terms in office; from 1966 to 1973 and 1977 to 1979....

, a native of Cork.

It takes the road under the River Lee
River Lee (Ireland)
The Lee is a river in Ireland. It rises in the Shehy Mountains on the western border of County Cork and flows eastwards through Cork City, where it splits in two for a short distance, creating an island on which Cork's city centre is built, and empties into the Celtic Sea at Cork Harbour on the...

. North of the tunnel, the ring-road joins the M8 motorway
M8 motorway (Ireland)
The M8 motorway is an inter-urban motorway in Ireland, which forms part of the road from the capital - Dublin - to Cork city. The 149 km motorway commences in the townland of Aghaboe, County Laois and runs through the counties of Kilkenny, North Tipperary, South Tipperary and Limerick,...

 to Dublin (north) and N8 road to the city centre (west), with the N25 continuing east to Waterford
Waterford is a city in the South-East Region of Ireland. It is the oldest city in the country and fifth largest by population. Waterford City Council is the local government authority for the city and its immediate hinterland...

. The tunnel was completed in May 1999, and carries nearly 40,000 vehicles per day as of 2005. This figure may rise further as the N25 ring-road's upgrades progress, notably with the recent opening of the Kinsale road roundabout
Kinsale road roundabout
The Kinsale Road Roundabout , sometimes nicknamed The Magic Roundabout, is a five-arm signalised roundabout located approximately 3km south of Cork city centre in Ireland at the junction of the N25 South Ring Road and the N27 South City Link/Airport Road.The South Ring Road has been constructed on...

 flyover and planned flyovers on the Sarsfield Road and Bandon Road Roundabouts.

The tunnel has two cells, each with two traffic lanes and two footpaths, and a central bore for use in an emergency only. Pedestrians and cyclists are expressly forbidden from using the tunnel. The exclusion of cyclists has been somewhat controversial as the feeder road is a dual-carriageway and so is open to cyclists, but the bye-law is applied because of space limitations and the obvious danger of cyclists in an enclosed tunnel.


The idea of a crossing of the River Lee downstream of the city came from civil engineers employed by Cork Local Authorities and the central government’s Department of the Environment in the late 1970s. Cork’s suburbs were expanding and traffic was rising as car ownership increased, but the city centre’s street plan, laid out in the late Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

, was ill equipped to cope. The engineers reasoned that the congestion in the city centre and its radial routes was quickly reaching intolerable levels. They pushed through Cork’s “LUTS” - Land Use and Transportation Study – plan, to lay down a twenty five year plan for the orderly growth of transport and land use in the greater Cork area. The transportation proposals combined construction of elements of a ring road, a downstream crossing, and computerized management of traffic on existing roads. This group of engineers became the Technical Steering Committee for the LUTS Plan and at that time consisted of Sean McCarthy, the former City Engineer, W.A. "Liam" Fitzgerald, his successor as City Engineer, Liam Mullins, Cork’s County Engineer, John O’Regan, his deputy, B.J. O’Sullivan, the Cork Harbour Engineer, and Sean Walsh and Declan O’Driscoll, the two Assistant Chief Engineering Advisers at the Department of the Environment responsible for the region. The location and type of crossing was not established by the LUTS plan.

No road development in Ireland prior to that date had required such a large investment, and therefore the plan met with some opposition on the grounds of cost. In 1980, Cork Corporation commissioned DeLeuw Chadwick O’hEocha, engineering consultants, to undertake a feasibility study of options for a major highway crossing of the River Lee downstream from Cork city centre. A team led by J.D. Shinkwin, Director of DeLeuw Chadwick O’hEocha, performed the study. The first stage of the report established that the crossing should be located in Dunkettle, rather than at Tivoli, closer to the city centre. The second stage endorsed an immersed tube tunnel as the preferred scheme versus a bridge (either fixed or opening span). The primary reasons were that a tunnel would have a lower construction cost relative to its utility, shorter approach gradients, lower environmental impact and no effect on shipping once built. While the construction costs for a two lane tunnel were marginally higher than for a two lane high-level bridge, the steep upward ramp for a high-level bridge would slow down cars and trucks as they climbed the bridge, thus reducing its peak capacity dramatically versus a tunnel or, alternatively, necessitating the addition of a climbing lane with significant additional costs. The other alternative considered by the Steering Committee was an opening span bridge. While this solution would avoid the ramp problem of a high-level bridge, traffic would halt whenever the bridge had to open. Shipping volumes into Cork's port area was rising steadily in the 1980s, which meant that an opening span bridge was becoming less attractive every year.
A sworn Public Inquiry into Cork Corporation's application for a "bridge order" providing for a two-lane tunnel was held in October 1985. The required inspector's report was submitted in January 1987 to the then Minister of the Environment, Pádraig Flynn
Padraig Flynn
Pádraig "Pee" Flynn is a former Irish politician. He was first elected to Dáil Éireann as a Fianna Fáil Teachta Dála in 1977. He was returned at each subsequent election until 1993...

. At that point, the report remained on the minister’s desk for some time. The formal reason for this was that the minister “decided that the question of the timing of the crossing should be considered in the broader context of the preparation by the Department of proposals for the medium to long term development of national roads. In this context the operational programme for roads … includes the proposal for the commencement of the downstream crossing during the programme period 1989-1993”.

In 1989, the government recommended a further feasibility study to consider the need for a crossing and the technical, economic and operational aspects of the various crossing options. The study confirmed the findings of the original Feasibility Study
Feasibility study
Feasibility studies aim to objectively and rationally uncover the strengths and weaknesses of the existing business or proposed venture, opportunities and threats as presented by the environment, the resources required to carry through, and ultimately the prospects for success. In its simplest...

. A further Public Inquiry
Public inquiry
A Tribunal of Inquiry is an official review of events or actions ordered by a government body in Common Law countries such as the United Kingdom, Ireland or Canada. Such a public inquiry differs from a Royal Commission in that a public inquiry accepts evidence and conducts its hearings in a more...

 was held, with hearings in July and December 1990, which considered further the alternative of a four lane crossing rather than the planned two lane crossing.

In 1992, the Minister approved a Bridge Order for a four lane immersed tube tunnel. In the intervening time, the Irish government had also established the National Roads Authority
National Roads Authority
The National Roads Authority is a state body in the Republic of Ireland, responsible for the national road network. The NRA was established as part of the Roads Act 1993 and commenced operations on 23 December 1993 in accordance with S.I. 407 of 1993.County councils remain responsible for local...

 (N.R.A) to advance the long term development of the national roads network. Declan O’Driscoll was appointed the Chief Engineer of that authority and together with J.D. Shinkwin, Director of Ewbank Preece OhEocha, and W.A. Fitzgerald, Cork City Engineer, formed an informal Technical Steering Committee for the Tunnel Project.

Financing and contracting

The IR£70 million design and construct contract was awarded by the Cork Corporation on behalf of the National Roads Authority
National Roads Authority
The National Roads Authority is a state body in the Republic of Ireland, responsible for the national road network. The NRA was established as part of the Roads Act 1993 and commenced operations on 23 December 1993 in accordance with S.I. 407 of 1993.County councils remain responsible for local...

. The NRA received financial assistance from the Cohesion Fund of the European Union.

In the early 90s, Ewbank Preece OhEocha (formerly DeLeuw Chadwick OhEocha, and later to become part of Mott MacDonald) supervised a major geotechnical investigation, conducted a hydraulic study of the river, and carried out an environmental impact study. Ewbank Preece OhEocha, in association with Symonds Travers Morgan, produced a conceptual design and tender documents for Cork Corporation on a design and construct format based on geometric and performance specification. Thirteen parties showed interest in the contract. From these, four consortia were selected and Cork Corporation made a final contract decision in December 1994. As is typical on a large-scale project of this type, the chosen contractor was a joint venture of Tarmac Walls JV, formed by Tarmac Construction
Tarmac (company)
Tarmac is a company that is based in Wolverhampton in the United Kingdom and operates internationally. The company produces aggregates and road-surfacing materials, including tarmacadam, from which the company's name is derived...

, now a division of Carillion, and P.J. Walls (Civil) Ltd., part of Ireland's Walls Group. Subcontractors then handled many of the key tasks of construction.


Construction involved the excavation of a large casting basin where the tunnel elements or pieces were constructed. After construction of elements was complete, the casting basin was filled with water and joined to the adjacent River Lee
River Lee (Ireland)
The Lee is a river in Ireland. It rises in the Shehy Mountains on the western border of County Cork and flows eastwards through Cork City, where it splits in two for a short distance, creating an island on which Cork's city centre is built, and empties into the Celtic Sea at Cork Harbour on the...

, each element was floated out and sunk into position into a carefully dredged river bed. The road surface was laid and the tunnel opened for traffic in 1999.

Construction techniques

The chosen method of construction was the immersed tube
Immersed tube
An immersed tube is a kind of underwater tunnel composed of segments, constructed elsewhere and floated to the tunnel site to be sunk into place and then linked together. They are commonly used for road and rail crossings of rivers, estuaries and sea channels/harbours...

 technique. In this method, a trench is dredged in the bed of the water channel. Tunnel sections are constructed in the dry, for example in a casting basin, a fabrication yard, on a ship-lift platform or in a factory unit. The ends of the section are then temporarily sealed with bulkheads. Each tunnel section is transported to the tunnel site - usually floating, occasionally on a barge, or assisted by cranes. In the Jack Lynch Tunnel, the 610 m long reinforced concrete immersed tube tunnel is made up of five elements, each around 120 m long, 24.5 m wide and 8.5 m high. These were constructed in a casting basin located partially on the line of the tunnel south of the river at Mahon. The northern approach was formed by a 120 m long floated open ‘boat’ section – the first of its kind.

Excavation and dredging

Dredging International was the chosen dredging contractor, and the value of the dredging contract is stated by them at €12.4 million. The scope of works consisted of dredging the main tunnel trench and subsequently backfilling the completed construction with sand and gravel. The contract provided also for restoration of the riverbed profile and the addition of a rock protection layer. Between May 1996 and March 1999, the company excavated 785,000 tonnes of silt and alluvium and 300,000 tonnes of sand and gravel.

The trench was dredged primarily by a series of specialized vessels, in several stages and with different equipment. Much of the main trench for the Lee Tunnel was excavated by the backhoe dredger “Zenne”. Two barges were used to transport the dredged material 19 km (12 mi) downriver and from there to a disposal site four miles offshore. The cutter dredger “Vlaanderen XIX” removed the underlying fluvioglacial material. A second cutter dredger, “Vlaanderen XV”, was deployed to breach the casting basin perimeter, or "bund". A rock layer was encountered on part of the trench line, which was dealt with by the jack-up platform “Zeebouwer”. The “Big Boss” vessel was employed to remove the rock. This backhoe dredger was equipped with a “Backhoover” (in effect, a “mini” precision dredger). This system proved extremely effective in removing very thin layers of recently deposited material immediately prior to immersion of the tunnel elements.

Constructing the immersed tube

Building the tunnel structure required the pre-casting of 5 tunnel segments and an open boat unit. These were constructed in a casting basin south of the river at Mahon. Each segment was 122 m long and weighed approx 27,000 tonnes. Contractors Tarmac Walls JV engaged RMD Kwikform, a global construction formwork and shoring solutions company, for the formwork on the tunnel and open section elements of the river crossing.

Each box section measures approximately 24.5 m wide x 8.5 m high x 122 m long and comprised two 9.8 m wide dual lane traffic tubes and a 1.35 m wide twin walled central tube for services and emergency access. The 1200 mm thick base slab was cast first, followed by the 500 mm thick central walls. The outer walls and roof were cast together in a single operation, in six nominal 20 m lengths, using special traveling formwork. This was struck inside the formed section, moved along to the next length and then jacked up into position, each within a 72 hour cycle. Each 1000 cubic metre pour required approximately 1500 square metres of formwork. The inside shutters for the outer walls were vertical steel section panels and Alform Beam walers, which were attached to the top slab of the special steel traveller, while the outer shutters were crane handled vertical steel section panels with Alform Beam or steel channel walers.

The open top boat unit, measuring approx 40 m wide (including two 7.2 m wings at its widest point) x 120 m long and up to 10 m high was cast in two operations using standard formwork. The boat unit and all the tunnel section elements were cast using grade 40N concrete with a percentage of ggbfs cement replacement, reinforcement being high strength and 16 to 40 mm diameter.

Tunnel operation

The road surface was laid in 1998/1999 and the tunnel opened for traffic on 31 May 1999, roughly 20 years after the first formal studies had been prepared. The final cost of the whole scheme including feeder roads and not just the tunnel itself was IR£105 million (approx €133 million). The tunnel has two separate two-lane bores (each lane 3.75 m wide). There is a service walkway about 1 metre across which doubles as an emergency escape. During periods of maintenance, one tube may be closed and the other used for bi-directional traffic.
The environment within the tunnel is controlled by an array of monitors and a closed circuit TV and traffic control system. External photocells linked to the computer management system provide a level of tunnel lighting most compatible with ambient light levels outside. To assist drivers in adjusting their eyes, lighting gradually brightens as they approach an exit.

Jet fans located within niches in the roof of the immersed tube sections provide longitudinal ventilation, and the tunnel is equipped with fire and life safety equipment.

Despite the cost of its construction and operation the tunnel is not tolled
Toll road
A toll road is a privately or publicly built road for which a driver pays a toll for use. Structures for which tolls are charged include toll bridges and toll tunnels. Non-toll roads are financed using other sources of revenue, most typically fuel tax or general tax funds...

. The Feasibility Study for the tunnel envisaged that the crossing could have a toll of 30 pence (in 1981 IR£) (approximately €1.05 in 2007 money), but the concept of a toll was dropped after political opposition. It was felt that, because of the proximity of the tunnel to the city, the imposition of tolls would tend to encourage some drivers to avoid the tunnel and continue using the city centre streets thus minimising the benefits of the tunnel.

An immersed tube tunnel of similar length has been constructed in Limerick, as part of Limerick's south ring road. The Limerick Tunnel
Limerick Tunnel
The Limerick Tunnel is a 675m long, twin-bore road tunnel underneath the River Shannon on the outskirts of Limerick City. The tunnel forms part of the N18 Limerick Southern Ring Road. The tunnel is tolled....

 was constructed under a Public-Private Partnership
Public-private partnership
Public–private partnership describes a government service or private business venture which is funded and operated through a partnership of government and one or more private sector companies...

 scheme signed with Direct Route (Limerick) Ltd. and is tolled (and has resulted in some political opposition in Limerick as the Jack Lynch Tunnel is also an inner city relief route but is not tolled).

See also

  • Roads in Ireland
    Roads in Ireland
    The island of Ireland, comprising Northern Ireland and the Republic of Ireland, has an extensive network of tens of thousands of kilometres of public roads, usually surfaced. These roads have been developed and modernised over centuries, from trackways suitable only for walkers and horses, to...

  • Motorways in the Republic of Ireland
    Motorways in the Republic of Ireland
    In Ireland, the highest category of road is a Motorway , indicated by the prefix M followed by one or two digits...

  • National primary road
    National primary road
    A national primary road is a road classification in the Republic of Ireland. National primary roads form the major routes between the major urban centres. There are over 2,700km of national primary roads. This category of road has the prefix "N" followed by one or two digits...

  • National secondary road
    National secondary road
    A national secondary road is a category of road in Ireland. These roads form an important part of the national route network, but are secondary to the main arterial routes which are classified as national primary roads. National secondary roads are designated with route numbers higher than those...

  • Regional road
    Regional road
    A regional road in Ireland is a class of road not forming a major route , but nevertheless forming a link in the national route network. There are over 11,600 kilometres of regional roads. Regional roads are numbered with three digit route numbers, prefixed by "R" A regional road in Ireland is a...

  • Local Roads in Ireland
    Local Roads in Ireland
    A Local Road in Ireland is a class of public road not classified as a National road or as a Regional road but nevertheless forming a link in the national network of roads...

  • Atlantic Corridor
    Atlantic Corridor
    The Atlantic Corridor is a road project in Ireland that eventually will link Waterford in the South-East to Letterkenny in the North-West by high-quality dual carriageway or motorway. A major infrastructure project, the scheme was announced as part of the Transport 21 project launch in 2005, and is...

  • Dublin Port Tunnel
    Dublin Port Tunnel
    The Dublin Port Tunnel is a road traffic tunnel in Dublin, Ireland, that forms part of the M50 motorway....

  • River Suir Bridge
    River Suir Bridge
    The River Suir Bridge is a cable-stayed bridge over the River Suir in Ireland. It was built as part of the N25 Waterford Bypass, and opened to traffic on the 19 October 2009, some ten months ahead of schedule...

  • History of Roads in Ireland
    History of Roads in Ireland
    There have been routes and trackways in Ireland connecting settlements and facilitating trade since ancient times and the country now has an extensive network of public roads connecting all parts of the island.-Early history:...

  • Trunk Roads in Ireland
    Trunk Roads in Ireland
    Ireland has an extensive network of public roads which connect all parts of the country with each other. Roads in Ireland are currently classified as motorways, National Primary routes, National secondary routes, Regional roads and Local roads. The introduction of this classification system began...

  • National Roads Authority
    National Roads Authority
    The National Roads Authority is a state body in the Republic of Ireland, responsible for the national road network. The NRA was established as part of the Roads Act 1993 and commenced operations on 23 December 1993 in accordance with S.I. 407 of 1993.County councils remain responsible for local...

  • Road signs in the Republic of Ireland
    Road signs in the Republic of Ireland
    Road signs in Ireland mostly differ from the traffic signs used elsewhere in Europe. Directional signage is similar to that of the United Kingdom, but is bilingual. Distances are in kilometres. Apart from directional signage, the basic prohibitory signs such as "no left turn" and "no right turn"...

  • Road speed limits in the Republic of Ireland
    Road speed limits in the Republic of Ireland
    Road speed limits in the Republic of Ireland apply on all public roads in the country. These are signposted and legislated for in kilometres per hour. Speed limits are demarcated by regulatory road signs . These consist of white circular signs with a red outline. Speed limits are marked in black...

  • Vehicle registration plates of Ireland
  • Northern Irish Vehicle Registration Plates
  • Transport in Ireland
    Transport in Ireland
    Most of the transport system in Ireland is in public hands, either side of the Irish border. The Irish road network has evolved separately in the two jurisdictions Ireland is divided up into, while the Irish rail network was mostly created prior to the partition of Ireland.In the Republic of...

  • List of Ireland-related topics

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.