Heritage and conservation register
|Name of Item||Carrathool Bridge over Murrumbidgee River|
|Type of Item||Built|
|Item Sub-Type||NSW Allan Truss Bridges|
|Address||**** **** Carrathool 2711|
|Local Government Area||Carrathool|
|Current Use||Road bridge|
|Former Use||Road bridge|
Statement of significance
|Statement of significance||Completed in 1922, the Carrathool bridge is an Allan type timber truss road bridge, and has a rare Bascule type lift span to allow river craft to pass. In 1998 it was in good condition.
As a timber truss road bridge, it has strong associations with the expansion of the road network and economic activity throughout NSW, and Percy Allan, the designer of this type of truss.
Allan trusses were third in the five-stage design evolution of NSW timber truss bridges, and were a major improvement over the McDonald trusses which preceded them. Allan trusses were 20 per cent cheaper to build than Mc Donald trusses, could carry 50 per cent more load, and were easier to maintain.
The Bascule lift span is a rare feature, and has associational links with the historic river trade, and has much to reveal about late 19th century civil engineering and manufacturing technology.
In 1998 there were 38 surviving Allan trusses in NSW of the 105 built, and 82 timber truss road bridges survive from the over 400 built.
The Carrathool bridge is a representative example of Allan timber truss road bridges, and is assessed as being State significant, primarily on the basis of its technical and historical significance.
|Date Significance Updated||02 March 2007|
|Construction years||**** - 1924|
|Physical description||Carrathool Bridge is an Allan type timber truss road bridge with a steel lift span. It has 2 timber truss spans, each of 21.8m (72ft). There are three timber approach spans, then two Allan trusses, then a bascule lift span followed by a steel track span and one remaining timber beam span, giving the bridge an overall length of 115.5m (379ft).
The lift span is of the Bascule type and is supported on cylindrical twin iron piers. The timber truss spans are supported on timber trestles. The bridge provides a carriageway with a minimum width of 4.3m.
A timber post and rail guard rail extends the full length of the bridge.
|Original condition assessment: 'Good' (Last updated: 22/10/1998.) 2007-08 condition update: 'Fair.' (Last updated: 17/4/09.)|
|Modifications and dates||****|
|Date condition updated||17 April 2009|
|Historical notes||The Carrathool bridge is an Allan type timber truss road bridge and was completed in 1922.
Timber truss road bridges have played a significant role in the expansion and improvement of the NSW road network. Prior to the bridges being built, river crossings were often dangerous in times of rain, which caused bulk freight movement to be prohibitively expensive for most agricultural and mining produce. Only the high priced wool clip of the time was able to carry the costs and inconvenience imposed by the generally inadequate river crossings that often existed prior to the trusses' construction.
Timber truss bridges were preferred by the Public Works Department from the mid 19th to the early 20th century because they were relatively cheap to construct, and used mostly local materials. The financially troubled governments of the day applied pressure to the Public Works Department to produce as much road and bridge work for as little cost as possible, using local materials. This condition effectively prohibited the use of iron and steel, as these, prior to the construction of the steel works at Newcastle in the early 20th century, had to be imported from England.
Allan trusses were the first truly scientifically engineered timber truss bridges, and incorporate American design ideas for the first time. This is a reflection of the changing mindset of the NSW people, who were slowly accepting that American ideas could be as good as or better than European ones. The high quality and low cost of the Allan truss design entrenched the dominance of timber truss bridges for NSW roads for the next 30 years.
Percy Allan, the designer of Allan truss and other bridges, was a senior engineer of the Public Works Department, and a prominent figure in late 19th century NSW.
Timber truss bridges, and timber bridges generally were so common that NSW was known to travellers as the "timber bridge state".
Constructed in response to heightened public pressure for a bridge to replace the river punt, funding for work was drawn partly from the local community, and partly from the Department of Public Works. That the local people had to pay for half of what should have been a national work was deplored by the then Mayor of Hay, who was a vocal advocate for the rights and the development of the Riverina region.
|Heritage Listing||Reference Number||Gazette Number||Gazette Page|
|Heritage Act - State Heritage Register||01460|
|National Trust of Australia register|
|Register of the National Estate|
|Heritage Act - s.170 NSW State agency heritage register|
Assessment of Significance
|Historical Significance||Through the bridge's association with the expansion of the NSW road network, its ability to demonstrate historically important concepts such as the gradual acceptance of NSW people of American design ideas, and its association with Percy Allan, it has historical significance.|
|Aesthetic/Technical Significance||The Bascule lift span is a distinctive visual feature, embodying the spirit of late 19th century aesthetics. Further, its function can be clearly seen, and shows unambiguously the innovation which went into its design. The bridge exhibits the technical excellence of its design, as all of the structural detail is clearly visible. In the context of its landscape it is visually attractive. As such, the bridge has substantial aesthetic significance.|
|Social Significance||Timber truss bridges are prominent to road travellers, and NSW has in the past been referred to as the "timber truss bridge state". Through this, the complete set of bridges gain some social significance, as they could be said to be held in reasonable esteem by many travellers in NSW.|
|Research Significance||The bridge is highly technically significant because it is an example of an Allan truss, and is representative of some major technical developments that were made in timber truss design by the Public Works Department. The Bascule lift span is a rare feature, and has associational links with the historic river trade, and has much to reveal about late 19th century civil engineering and manufacturing technology.|
|Rarity||In 1998 there were 38 surviving Allan trusses in NSW of the 105 built, and 82 timber truss road bridges survive from over 400 built. Three bascule lift span bridges survive in NSW, and the Carrathool bridge is the only one in a timber truss road bridge.|
|Representativeness||Representative of Allan truss bridges|
|Written||Department of Main Roads, NSW||1987||Timber Truss Bridge Maintenance Handbook|
|Written||Fraser, D J||1985||Timber Bridges of New South Wales|
|Written||Allan, Percy||1924||Highway Bridge Construction. The practice in New South Wales.|
|Title||Year||Author||Inspected by||Guidelines used|
|Relative Heritage Significance of all Timber Truss Bridges in NSW||1998||McMillan Britton & Kell||Yes|
|Roads and Maritime Services Region||South West|
|CARMS File Number||80.66|
|Conservation Management Plan||****|