This challenging project involved the demolition of the existing reinforced concrete cantilever walkway at New Road, Bideford and replacement with a new quay wall structure. The river is tidal and the site was adjacent to a SSSI as well as being located within an urban residential area. All works were carried out from a stone platform on the river bed, working between tides.
Dawnus constructed a tied sheet pile wall with a reinforced concrete and masonry retaining wall facing. In total, 71 no. 15m long sheet piles were driven to refusal to form the main wall, using an excavator mounted rig working on the foreshore. The sheet piles were anchored back using two rows of 50mm diameter inclined rock anchors of circa 15 to 17m length. On completion of the wall, a concrete walkway structure was constructed above it, which cantilevered out over the river to provide a new walkway.
We re-constructed a 12m section of the existing Grade One listed bridge masonry parapet as part of the works, along with the permanent diversion and extension of an existing South West Water outfall. On completion the river bank was reinstated and approximately 600m2 of stone pitched revetment placed to protect the bank from scour.
Dawnus considered that it was impractical and too risky, due to lack of space between the quayside and the public highway, to attempt to carry out the demolition from the top of the existing quay side. A platform of clean stone was created instead at the base of the quay wall. This raised the level platform but kept the demolition operation away from the edge of the public highway and also through its height increased the amount of time before the tide flooded the working area. This methodology proposed by Dawnus provided cost savings by avoiding the use of temporary works platforms within the river. In addition, by installing all works from the river bed two-way traffic was maintained at all times.
Devon County Council