On Location

Coalcliff Tunnel

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An innovative solution for a heritage icon.

The Coalcliff Tunnel, built in 1888, is of local historical significance as one of the first tunnels built for steam trains on the Illawarra line, Sydney, NSW Australia.


The tunnel also has technical significance as the second longest tunnel on the Illawarra line and for its ability to demonstrate late 19th century railway tunnel building technology. The tunnel is representative of the late 19th century tunnels built south of Waterfall to connect the Illawarra line through to Sydney from Scarborough.


The single-track oviform brick tunnel is 1000 metres in length (60.337- 61.337 Km) and due to the difficulty in building a second tunnel it remains a single line with both connecting lines being duplicated in 1915. In 1986, the line was electrified as far as Wollongong necessitating the installation of new electrical infrastructure within the tunnel.


From a maintenance perspective, the Coalcliff Tunnel has been a longstanding challenge for Sydney Trains. To address the issue, they approached Rhomberg Sersa Australia (RSA) to provide the IVES system, which was identified as the most suitable by an independent design report. RSA took up the challenge and has been working with Sydney Trains to turn this project into reality ever since.


To commence the long-term solution, RSA were requested to trial the IVES system in the first 50 kilometres of the tunnel during Easter 2023 possession, allowing its performance to be monitored. The project involved removing the first 50 metres of track, removing all the ballast, and lowering the tunnel using a cold milling machine. Furthermore the team performed vigorous tunnel cleaning and dewatering over the extended weekend. Then Asphalt was placed in two layers, constructed a central drainage channel, laid the IVES block for 15 metres, and reinstated the transitions using ballasted track.


In conclusion, the Coalcliff Tunnel is a significant historical and technical landmark. The use of modern track slab solution such as IVES will ensure the track performance, making it a safer and more reliable transport link for generations to come.

Project Coalcliff-Tunnel

  • Location: Sydney, Australia
  • Client: Sydney Trains
  • Contract: Slab Track in the tunnel 
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