Challenges

• Two options were considered for the deteriorated twin 1500 mm pipes. The first was the traditional method of replacing the culvert with new reinforced concrete pipes on a new alignment. This would have caused major disruption to the busy South Eastern Freeway traffic and considerable angst and economic loss. The preferred option was to resleeve of the existing steel pipes with minimum 1050 mm diameter reinforced concrete pipes. The above-ground works were contained within the interchange and the resleeving option eliminated extensive excavation. This approach avoided disruption to the free flow of traffic on the freeway, and minimised disruption and delays on the access ramps.
• The key to the construction was the innovative design of a motorised pipe trolley to drive inside the 1050 mm concrete pipe. The trolley was operated from the surface by remote control. It had three sets of hydraulics to lift the new 1050 mm pipe, transport it within the existing culvert and place it into position. CCTV cameras enabled personnel to monitor the works remotely, without the need to enter the confined space.
• A concrete jacking chamber was designed and constructed one third of the way along the existing culvert. This enabled pipe sections to be lowered to invert level and installed using the motorised trolley. Other ancillary structures included the upgraded inlet and outlet structures, including scour protection, to ensure the 100 year design life was achieved.
• Regular monitoring of water quality demonstrated significant reductions in turbidity during and following the project. A natural spring located near the works was not disrupted. Site works were closely managed to contain any spread of Phytophthora and weeds. The project significantly improved the amenity of the whole site.

Working in a confined space in the third wettest summer on record had the potential for disaster. However, innovative technology and Leed’s highly developed safety systems were combined to deliver a safe workplace. In particular, the pipe trolley contributed significantly to the safety of the confined space operations.