A replacement gas pipeline will be housed in the 5km tunnel that Mary has dug beneath the Humber from Goxhill in North Lincolnshire to Paull on the river’s north bank. National Grid and project partners Skanska, Porr and AHak have bid farewekll to the 160m-long TBM, which is now heading away to be refurbished for next tunnelling job.
Mary’s breakthrough too place at Paull on 10 September, after which she as dismantled and lifted to the surface ready to be shipped back to Herrenknecht in Germany.
For the last 18 months, she has been steadily making her way from Goxhill on the south side of the river to Paull on the north bank, constructing a tunnel nearly 5km long and a 3.65m diameter. The excavated material – mostly chalk - is being used to help restore a former quarry nearby.
Steve Ellison, lead project manager, capital delivery, for National Grid, said: “Completing the tunnel beneath the Humber is a major milestone for the project team and our project partners. It’s the first time a tunnel has been constructed beneath the River Humber and a fantastic achievement for everyone involved. Mary has completed a fantastic feat of engineering and it’s great to see her on her way back to Germany where as much as possible will be refurbished and renewed to get her ready for her next tunnelling job.
“The next steps for us here under the River Humber involve clearing the pipes, cables and ancillary equipment that has been servicing the tunnel boring machine and preparing for the world record breaking pipeline installation early next year.”
In spring 2020, two hydraulic thrust machines will start the push of eight 610- long, 850t sections of pipe on rollers into the new tunnel from the Goxhill side. The pipes will be pushed at about one metre per minute into the tunnel which will have been flooded with water to aid installation.
When one pipe section has been installed, the next will be moved into position, welded to the one in front, and the push will continue until all 5km of pipeline is installed beneath the river. When complete it is expected to be the longest hydraulically inserted pipe in the world.