The final section of a gas transmission pipeline has been successfully pushed through a tunnel beneath the Gladstone harbour to the Santos GLNG plant on Curtis Island.
The 120 pipeline segments, each measuring 36 metres in length, were welded together and pushed gradually through the 4.3 kilometre tunnel using a large hydraulic jack, and seawater to buoy the 42 inch pipe.
The operation took around four weeks to complete.
The 3.45 metre under-sea tunnel runs eight metres below the sea bed, and was drilled with a tunnel boring machine, 100 metres long and weighing 277 tonnes.
Santos vice-president downstream GLNG Rod Duke said the pipeline would soon be ready to deliver gas to Curtis island.
"This year is about delivering milestones across Santos GLNG," Duke said.
“Santos GLNG delivered the first under-sea crossing for Queensland’s CSG to LNG industry.
"We're particularly proud of this achievement, given the innovation and expertise required to achieve a marine crossing like this one.
Duke also said he pipeline route will be fully rehabilitated.
“When we set out to build a 420 kilometre pipeline from Fairview field to Gladstone we promised to safeguard the environment,” he said.
"Our under-sea tunnel has allowed us to cross The Narrows without disturbing the local marine environment and with minimal impact to the surrounding coastal environments.
"In the coming weeks the marine crossing pipe will be connected to the rest of Santos GLNG's 420 kilometre pipeline.”
Pipeline pre-commissioning works are well underway, with clean and gauge activities nearing completion and about half of the required hydro-testing completed.
The gas transmission pipeline is being built by Santos GLNG’s contractor Saipem Australia, while the tunnel was constructed by subcontractor Thiess.