Leinster Bridges Rehabilitation Contract 1 – 2013   Part 1: Kilkenny & Laois Bridges

AtkinsRéalis was commissioned by the Transport Infrastructure Ireland (TII) to design and supervise Leinster Bridges Rehabilitation Contract 1 – 2013 Part 1. This part of the project involved the rehabilitation of five bridges in Counties Laois & Kilkenny. The bridges rehabilitated were Mooney’s Crossroads (Wandesforde) Bridge and Mooney’s Crossroads Culvert.   Both are masonry arched bridges on the N78 spanning the river Douglas in County Laois. Glenahane Bridge, also on the N78 in County Laois, is a single span reinforced concrete deck built on the masonry abutments of a previous structure. Gloreen Stream Bridge is on the old N8 just north of Abbeyleix and is a relatively modern single span reinforced concrete bridge. Clashduff Lower Bridge, which carries the N78 over a tributary of the Dinin river near Castlecomer in County Kilkenny, is another masonry arched bridge.

All of the bridges were in need of cleaning and de-vegetation and most had suffered some form of scour damage to abutments and paved beds from storm flows. Some masonry bridges had sections of retaining wall and spandrel that had collapsed. To rehabilitate the bridges, abutments were underpinned and grouted, rock amour bank protection and stone pitching was placed in river beds, masonry joints were repointed and missing stones sensitively replaced.

The most challenging operation was the reconstruction of the masonry retaining walls. At Wandesforde Bridge a 25 metre long by 5m high section of retaining wall along the N78 roadway was rebuilt using a proprietary reinforced earth Terratrel system. The westbound lane was closed to allow for excavation while traffic flow was maintained using a shuttle temporary traffic management. Because of the restricted site available the face of the temporary excavation for the wall reconstruction was 70⁰ and was stabilised with reinforced shotcrete. The Terratrel reinforced earth system was installed to retain the road and was clad with selected local masonry to match existing. See photos of before and after reconstruction.

Apart from the remedial work, the project included the provision of new drainage and river outfalls, new parapet rails and walls, site fencing, safety barriers and, in the case of the reinforced concrete bridges, deck widening.

All of the bridges span rivers and some are fish important. We worked closely with IFI and NPWS during all phases of the project. Appropriate Assessment screening was undertaken by AtkinsRéalis Environmental team and appropriate environmental measures such as flumes, settling lagoons and temporary booms were provided in the rivers during construction. Gloreen stream was particularly environmentally sensitive as it is located upstream of a colony of rare fresh water pearl mussels (FWPM). A specialist survey was undertaken by ASU, UCC to locate the FWPM and they were found at the confluence of Gloreen Stream and the River Nore. A specialist bat survey was undertaken at all masonry bridges and where appropriate mitigation measures were incorporated into the works.