Replacement of cast iron piers on an 1886 wrought iron truss bridge in New South Wales, Australia – the challenge of preserving heritage significance during major rehabilitation work

The Namoi River Road Bridge is a colonial era high level wrought iron lattice truss bridge crossing the Namoi River (Manilla) built in 1886 to replace a dangerous river crossing. The bridge was part of the main road between Sydney (New South Wales – NSW), and Brisbane (Queensland), with the opening of the bridge allowing wool trade from the northern extents of the colony of NSW to be exported via the Port of Sydney. The six approach spans crossing the southern flood plain have history of differential settlement due to ground conditions which has resulted in damage to five bridge piers and variations to the vertical alignment of the bridge. This paper describes the method employed to restore the vertical alignment of the bridge and replace the damaged piers whilst ensuring retention of the structure’s cultural heritage significance, enabling the bridge to continue to operate as part of the NSW State Road network.