After inspection of the bridge at Longmuir, the existing structure was found to be in poor condition with widespread deterioration of the existing masonry arch barrel which had suffered a partial collapse at the West end.
The steel beams at the East end were badly corroded and the invert of the culvert was severely obstructed with silt and the abutments had localised areas of displaced stones.
The decision was made to replace the culvert.
Covanburn provided a full programme of works to the client which was agreed beforehand.
The replacement culvert comprised reinforced precast concrete planks supported on refurbished existing abutments with the culvert requiring to be extended at each end. The existing abutments needed to be repointed on each face and the stone work reinstated as required.
During the works, the road was fully closed to vehicular traffic. However, Covanburn provided a temporary, pedestrian diversion by means of a timber footbridge to allow locals and cyclists to bypass the works safely.
Following an inspection and assessment of the remaining abutments, the design for the replacement slabs was commissioned by Covanburn and carried out by Blyth and Blyth in Glasgow.
Once tested and fully cured, the slabs were transported to site.
New gabion basket wing walls were required at each end of the culvert. Following that the verges were re-constructed and the vehicle restraint barrier re-installed.
Finally, the road construction was fully reinstated with staggered joints.
Covanburn delivered the replaced culvert back to the clients to specification and on time.