A £150 million gas pipeline located 30 metres underneath the River Humber has become operational, National Grid has announced.
The Feeder 9 project was begun in 2016 with joint venture project partners Skanska, A.Hak and Porr. It replaces a trench-laid gas pipe which had become exposed.
In July National Grid announced it had completed the insertion of a 5km steel pipeline through the tunnel under the river, which measures 3.65 metres in diameter.
Eight 620-metre pipe sections, each weighing 850 tonnes, were driven through the tunnel one after another on rollers by two hydraulic thrust machines.
Once one section had been inserted, the next was lined up at the entrance to the tunnel and they were welded together before the pushing continued. The process was repeated until all five kilometres had been laid.
The pipes were pushed from the Goxhill side of the river at a rate of around one metre per minute. To aid the insertion, the tunnels were flooded with 50,000 cubic metres of purified water – enough to fill 16 Olympic swimming pools.
As part of the national transmission system the new pipeline connects the East coast terminal at Easington to the wider gas network. Following commissioning, it can transport between 70 to 100 million cubic metres – around a quarter of Britain’s gas.
Emma Ford, head of gas construction for National Grid, said: “Complex engineering projects such as these require a huge amount of skill and dedication from all those involved. To have delivered this ahead of the cold winter months despite Covid-19 restrictions is a fantastic achievement.”
James Holmes, operations director for Skanska, said: “Working with A.Hak and Porr we have delivered a project that will help ensure a reliable and resilient supply of up to 25 per cent of Britain’s gas.
“It has been a real feat of engineering that has been delivered thanks to a collaborative team spirit which has been created over the past four years.”