For Dundalk Western Bypass, procured under a PPP, we designed over 12km of dual carriageway plus 14 major structures – and helped develop value engineering solutions in critical areas such as bridge, drainage and pavement design
The objective of this high profile project was to complete the motorway – around 12 km of dual carriageway and 14 principal structures including the Ballynahattin Rail Bridge - between North Dundalk in Co. Louth and Gormanstown in Co. Meath and to operate and maintain it as a toll road. The project was procured by means of a PPP (Public Private Partnership) contract.

The new-build section is a significant project in its own right, with 1.25 million m³ of earthworks as well as the 14 major structures The contractor identified the importance of achieving the earliest completion possible which placed special focus on design activities.

Designing for the upgrade of 42km of the existing M1 motorway, included checking compliance with newly introduced standards, represented a first for the National Road Network.

Value engineering played an important part in assisting the contractor to investigate alternatives in critical areas such as bridge design, drainage and pavement.

In the case of the underbridges, we helped the contractor by examining a number of alternative options which offered advantages as compared to the more traditional solutions. Selection of a generic solution involving the use of reinforced earth abutments and pre-cast beam decks resulted in significant programme savings. Drainage design was optimised by considering a range of options including kerb and gully solutions, concrete channel solutions and grass channels. Alternative attenuation solutions were also considered at outfall locations.

For the mainline pavements, CBM2 material was used as sub-base, to an analysed design – the first use of this material in Ireland.

Ballynahattin Rail Bridge posed a major challenge to all involved in the project. At 7,500 tonnes, this was the largest structure ever constructed using the Autoripage method. We carried out all the design work for the 40 degree skew bridge which was built off line and moved 44m into place during the Easter weekend 2005, resulting in the minimum curtailment of rail services between Dublin and Belfast. The 83m long structure was slid into position in a 72 hour possession period using the Autoripage technique. As well as designing all the permanent works we also checked the earthworks stability in the railway embankment.