Engineering marvels at foot of Blue Mountains

In the 1860s railway engineer John Whitton had to build a major bridge across the Nepean River and a great viaduct across Knapsack Gully for the western line to reach the Blue Mountains ridge and further west.

The 150th anniversary of its opening to Wentworth Falls is being celebrated in July 2017 with several steam train rides at venues across the Blue Mountains.

Contracts were let for various construction sites across the Mountains in the early 1860s. Work was well and truly underway by 1864.

The first and greatest challenge was to cross the Nepean River. Trains could not use punts or fords. They needed solid, sturdy bridges and this is what the NSW Engineer-in-Chief of Railways, John Whitton, designed for the Nepean crossing. 

The design was checked in Britain by his brother-in-law and renowned railway engineer, John Fowler.  

The flood of 1860 had carried off the nearby road bridge which was replaced by two punts. These were also washed away in a later flood.

Victoria Bridge was originally designed to carry two railway tracks but, because of this flooding, government decided that the new bridge should carry both a railway line and a single lane of road over the river, as a temporary solution.

Whitton, having witnessed the power of the Nepean floods, decided to raise the original bridge deck design by six feet.

His foresight was rewarded when Victoria Bridge, shortly after it was completed, survived a record high flood of the Nepean in 1867.

Victoria Bridge is a continuous iron through-bridge as the deck is between the girders rather than on top of them.

The three main girders, each spanning a clear 186 feet, were designed and constructed as one 594 feet long continuous structure with no separations over the piers, a novel structural feature for 1867.

This Victoria Bridge still stands proud to-day, 150 years after it was finished.

The next challenge, as the line approached the eastern escarpment of the Blue Mountains, was to cross Knapsack Gully at the head of Jamison Creek.

John Whitton designed a viaduct that would carry the line safely over this obstacle.

W. Watkins, who had completed the stone piers of the Victoria Bridge, was given the contract for construction of the Knapsack Gully Viaduct in March 1863. Work was completed in 1865.

The viaduct was constructed of sandstone quarried in the neighbourhood, and carried a single rail line on an incline of 1 in 30. It consisted of five spans of fifty feet and two of twenty feet each.

The final step to the top – the Lapstone Zig Zag – now had to be completed.​ 

  • Robyne Ridge is the publicity officer for Blue Mountains History Society.