RPS worked on Mulroy Bay Bridge in Co. Donegal from the very start, doing the preliminary and detailed design work, the Environmental Impact Statement and getting the project through planning and then supervising the construction of the bridge.  It’s one of the largest bridges in Ireland and it has been successfully constructed in an area of outstanding beauty, an extremely sensitive Special Area of Conservation and a Natural Habitat Area. 

“In construction terms it was a major engineering feat, using a 'balanced cantilever approach' of progressive construction of individual piers and the subsequent decks hanging off the pier in a balanced format”, says Tony Magee, Structures Director, RPS Group.  “We ensured protection of a unique Salmon farm beside the bridge by protecting and monitoring throughout construction.  The Bay also supports scallops, oysters and mussels. This Class A designated bay is the largest natural habitat of Scallop spat fall in Western Europe.”
  
The bridge replaces an old ferry that plied the bay to connect two communities up to mid 1960s. It served the entire transport needs of the community, including the local postal service.

The bridge is a high level and multi-span bridge across Mulroy Bay, County Donegal, with associated approach roads.  The bridge length is 340m and it comprises 5 spans, with a main span of 100 metres. 

The €17.5m project is the final part in a tourist route travelling westwards from Antrim, crossing Lough Foyle by ferry at Magilligan (Co Derry) to Greencastle (Co. Donegal) and again by ferry across the Swilly from Buncrana to Rathmullan and finally by the newly constructed bridge from the Fanad Peninsula to the Rosguill Peninsula.  Prior to the construction of the bridge, the journey time between the Fanad Peninsula and the Rosguill Peninsula, was up to 2 hours (50km). 

With the balanced cantilever method, the bridge is built from the piers by means of formwork travellers. The bridge advanced from the top of the piers symmetrically in segments 4m in length (load balancing method) to the mid span where it met the adjacent advancing section and was then 'stitched' together.

The use of the balanced cantilever construction method, for medium and long span concrete bridges, is recommended especially where scaffolding is difficult or impossible to erect e.g., over deep valleys, wide rivers, live motorways or in this case a tidal bay of extreme environmental importance.