Cape Peron Ocean Outfall, Western Australia
This project involved constructing the second largest pipeline ever installed by the bottom pull method, in a major operational exercise by world standards. The project team, in joint venture, was responsible for the fabrication and installation of the pipeline.
A critical aspect of the method of construction was the weight of the pipe, which weighed 10,000t on land, and a mere 350t submerged. Accurate measuring and weighing equipment ensured that the required negative buoyancy of the pipeline was achieved.
FEATURES:
This 4.2km long, 1,400mm diameter offshore pipeline was constructed using the bottom pull method, as follows:
- pipes were constructed on land into "strings", each 220m long concurrently, a trench was excavated offshore, through the surf zone requiring blasting and removal of cap rock on the seabed
- the pulling operation used a 600m long deep sea barge equipped with a 50t single drum pulling winch and linear pullers for mooring
- the pipe was then backfilled to provide pipeline protection, firstly with sand placed to the crown of the pipe, then a filter fabric and finally a layer of cobbled rock.
BENEFITS:
An established track record in marine construction ensured that proven construction methods were employed. The installation method, using a continuous bottom pull, reduced operational risks by enabling the installation to be conducted during a period of time when bad weather was least likely to be experienced at the project site. The method was also best suited for a pipeline of this length, which was necessary to allow effluent to discharge beyond the reef in deep water.
CLIENT: Metropolitan Water Authority
