| Historical notes: | During the 20-year period 1873-1893 there was a massive programme of public works in New South Wales, particularly in expanding the road and rail networks. It was a boom period that ended with a severe economic depression.Despite the boom conditions, the respective Chief Engineers, for Roads (William C Bennett) and for Railways (John Whitton) were constrained to economise by using as much local material as possible, consequently an enormous amount of hardwood timber was used for bridgeworks, mostly timber beam and timber truss bridges.However, there were many major rivers to be crossed, requiring long span bridges, for which no form of timber bridge was suitable. These large bridges had to be metal and supplied from England, a very expensive import cost to the successive colonial governments. Both Chief Engineers were British so they chose the widely used wrought iron lattice truss bridge in the half-through form. Twelve of these were built for the railways and 24 for roads. These two sets of iron lattice bridges are the most significant group of bridges of the colonial period. A high percentage are extant and still in use, 10 on railways and 18 on roads. The current railway lattice bridges are,1876 Macquarie River at Bathurst1881 Macquarie River at Wellington1882 Peel River at Tamworth1882 MacDonald River at Woolbrook1884 Murray River at Albury1884 Macquarie River at Dubbo1885 Murrumbidgee River at Narrandera1887 Lachlan River at CowraTwo former railway lattice bridges (1885 Georges River at Como and 1886 Parramatta River at Meadowbank) were converted for use by pedestrian/cycle ways. The 1871 lattice railway bridge over the Hunter River at Aberdeen was replaced by steel girders and demolished. (SHR)Despite the economic boom and 'railway mania' of the 1870s and 1880s, Engineer-in-Chief of the NSW Government Railways (NSWGR) John Whitton remained constrained by a longstanding Government decree to use local materials in bridge construction. While most new bridges were of timber construction, Whitton occasionally defied the 1861 decree, for example when designing bridges for large water crossings. One example of this was the introduction of wrought iron lattice girder bridges, originally for the crossing of the Hunter River at Aberdeen in 1871, and for 12 bridges in total up until 1887. Lattice girder bridges became a dominant technology for road and rail bridges until the 1890s (Fraser, 1995).Twelve lattice girder bridges were built between 1871 and 1887: at Aberdeen, Tamworth, Woolbrook, Meadowbank, Wagga Wagga, Albury, Bathurst, Wellington, Dubbo, Narrandera, Como, and Cowra. Ten of these bridges remain extant in 2010, with the wrought iron lattice bridges at Aberdeen and Wagga Wagga no longer extant. The bridges at Como and Meadowbank are no longer used as railway bridges and have been converted for use as pedestrian walkways/cycle ways.The Murrumbidgee River Underbridge at Narrandera, completed in 1884, is located on the now disused Narrandera to Jerilderie Line, and was the ninth lattice girder underbridge in NSW. |