National Grid’s 510 tonne tunnel boring machine has hit a major milestone after reaching the halfway point across the River Humber.
The tunnel will eventually house a replacement gas pipeline which will carry around 20% of the gas Britain needs.
The tunnel is made by a 150 tonne tunnel boring machine name Mary – after Mary Fergusson, the first female fellow of the Institution of Civil Engineers.
It has now reached the halfway point through the 5km journey under the River Humber in a feat that has taken 200,000 man hours.
Project Manager Steve Ellison said: “Mary has done a brilliant job to date and we and our contractors are delighted to have reached the halfway point on the tunnel.
“There is still a lot more work to, do but I would like to say a big thank-you to the 40-strong team of engineers who have worked around the clock in very challenging conditions to get us to this important milestone.
“The machine has pretty much been operating 24 hours a day with the odd shut-down for repair or maintenance since the tunnelling work started on 6 April 2018.”
Once the tunnel is finished, and Mary is removed from the tunnel via a shaft on the opposite bank of the river at Paull, the work on the next phase of the project will begin.
A new 42inch diameter gas pipeline will be laid inside the tunnel. This will replace the existing gas pipeline which currently crosses the river and is laid in a trench just below the river bed.
This pipe at risk of being exposed by shifting tides. Work has been carried out to keep it buried but the Humber Pipeline Replacement project offers a long-term solution.
Already, the eight ‘strings’ or sections of gas pipe which will be pushed into the tunnel have been laid out and welded on a vast pipe ‘field’ on the Goxhill site. Work to install them in the tunnel will take around a year to complete.