Orkney link secures supply
One of Europe's longest ever pipeline pull-backs has been carried out by Scottish water in Orkney. Oxana Latypova of GPS PE Pipe Systems explains
PS PE Pipe Systems has supplied plastic piping to carry out one of the longest pipeline pull-back schemes ever carried out in Europe: the Orkney to Shapinsay Undersea Link. Located two miles off the coast of Orkney Mainland, Shapinsay has just one village and a population of around 300. Historically, the drinking water supply for the island has been provided by seven boreholes, but only three of these remain operational and to safeguard the quality and security of supply, Scottish Water decided to connect Shapinsay to the water treatment works on Mainland.
The project involved installation of 1.4km of pipework on Shapinsay, 4km of pipework on Mainland and a 2km tunnel under the sea connecting the two islands. Following a rigorous procurement process, Scottish Water Solutions, the project delivery arm of Scottish Water selected contractor, George Leslie, to carry out the project. Working with their specialist subcontractor, Stockton Drilling, they drilled the 311mm diameter tunnel for the 180mm pipe from coast to coast, 20m below the sea bed, using directional drilling to divert the tunnel up to 15m below the rock head where required. PE pipe was specified with a high wall thickness of SDR6 to ensure sufficient tolerance to the stresses involved during the pull-back operation.
Scott Rowan from George Leslie, explains: “The maximum water pressure once the pipeline is in use will be in the region of 10 bar, but the stress on the pipe walls during the pull back operation will be extreme. PE pipe was specified for its durability and flexibility as it will need to follow the contours of the tunnel and have a long and maintenance-free service life.”
Ten metre sections of piping were butt-fused by the George Leslie team to create a 2km string weighing 28 tonnes, which was then laid out straight to enable pressure testing to be carried out prior to the pull-back operation. Once the tunnel was completed, the end of the pipe string was connected to the towing head using drill rods and the two-day operation to pull it back through the tunnel at the rate of 9m/minute began.
The undersea pipeline is now in place and the installation team has begun the open cut installation of the land-based pipeline. Shapinsay is expected to get its first taste of water from Mainland this month.
- Drinking water reed bed system nears completion The many benefits of natural wastewater systems will be illustrated by a £4.5M system scheduled to be up and running in... Read More >
- Innovation Zone: Aquam OSV and Manifold In this month's innovation feature, we look at a supply vehicle which uses a custom built manifold device designed for use... Read More >
- Peacehaven - at last The new sewage works for Brighton & Hove has finally been commissioned. Natasha Wiseman took a look around Read More >
- Striking it out: How can the industry cut down utility strikes? Utility strikes are both costly and potentially fatal. With tens of thousands believed to occur in the UK every year, how... Read More >
- Comment: Plastic pipes could contribute to circular economy The time is right to make use of recycled plastics for drains and sewers, and for the pipe industry to help minimise... Read More >
- Comment: Ease off the pressure to keep leaks in check Keeping leaks in check is a major challenge for water companies but one that can be met with variable speed drives to... Read More >
- Woolmans Wood: Driving down disruption Southern Water and Clancy Docwra discuss the challenges of keeping disruption to a minimum on a 30km mains replacement... Read More >
- Water theft: Laying down the law Whether it is unauthorised connections or the illegal use of standpipes, water companies are increasingly clamping down on... Read More >