One of Queensland’s biggest gas industry projects has been connected to the world, with a complex under water tunnel. It’s one of the longest trenchless marine pipelines ever built.
The Narrows Crossing Tunnel has been constructed under Gladstone Harbour, off the central Queensland Coast. It’s a vital link in a 420-kilometre underground pipeline route transporting coal seam natural gas from near Roma to the Santos GLNG facility on Curtis Island, where the gas is converted into liquefied natural form for export.
Contract miner Theiss required a technical solution to optimise productivity, while protecting the marine mangrove environment and causing minimal impact to the surrounding coastal areas. Theiss completed the works for Saipem Australia, the principal contractor on the multi-billion-dollar Santos GLNG Gas Transmission Pipeline Project.
National Precast member Precast Concrete Products, based in Carole Park in Brisbane’s west, was contracted to supply the precast concrete for the project. The 4.3-kilometre-long tunnel, with a 3.4-metre internal diameter, was constructed with high performance precast segmental lining.
Director Ian Coulter says precast concrete was chosen to ensure reliable delivery, easy segment installation and a high quality finish. “We had to specially manufacture 22,000 concrete segments for the tunnelling,” he says
The timeline of the project was challenging. According to Mr. Coulter, high-precision moulds were cast twice a day, six days a week using advanced concrete technology and curing methods: “That ensured we met the tight delivery schedule and meant the tunnel-boring machine could run uninterrupted around the clock.”
The precast segments were installed as the tunnel was bored and a cement-based grout was injected behind the segment lining to permanently seal the tunnel.
The Narrows Crossing Tunnel project has also been recognised for its innovation, with Theiss, Saipem Australia and Santos GLNG winning the prestigious 2014 Premier’s Sustainability Award in Australia, under the category “Innovation in Sustainable Technologies”.