Client and Designers: British Waterways
Osberton Top Turnover Bridge was a joint project between British Waterways and GallifordTry Construction through the BW North East Omnibus contract. The project involved the reconstruction of a red brick arched accommodation bridge that was in a very poor condition. A number of bricks were missing from the arch and there was extensive damage to one of the abutments. It was not deemed viable to strengthen the bridge and therefore it was demolished and replaced with a similar structure that would complement the local character of the Chesterfield Canal.
The new structure was built using bricks, selected to match the existing bridges with a similar arch profile though incorporating additional air draft for user safety. Eminently hydraulic lime mortar was used to construct the arch to allow free drainage and thermal expansion / contraction of the arch and then saddled to provide the necessary strength. In addition, recycled stone steps and copings were obtained and original springing blocks that contained historically important wear marks, resulting from the ropes used by horse drawn boats, were reused within the new structure.
During construction of the bridge, which lies within a County Wildlife Site, disturbance to surrounding trees and hedgerow was minimised by having a compact site compound. The hedgerow adjacent to the site was enhanced with locally occurring species when the construction phase was complete. An advance survey had shown that the original structure was used by a protected species, the Daubenton’s bat. Following consultation with English Nature and DEFRA, new roosting habitat was incorporated with the rebuilt structure (see Photo). Adjacent to the bridge eroded canal banks were reinstated and wildlife habitat created using a type of soft bank protection, coir roles, planted with locally sourced riparian plants (see photo).
The scheme was assessed by Dr Mark F Robinson, Waterway Conservation and Regeneration, British Waterways and verified by Dr Richard Hunt, Ove Arup and Partners.