Have you seen what looks like a layby halfway through the Liverpool to Wallasey section of the tunnel?
Here is why it is there.

Work started with construction by hand of an 8ft high pilot tunnel through sandstone under the River Mersey. It took about a year to complete. Then the giant laser-guided ‘Mersey Mole’ arrived to excavate the main tube.
Having previously been deployed on the construction of Pakistan’s vast Mangla Dam, the 35-tonne, 45-foot long machine carved a route under the River Mersey, leaving a concrete lined tunnel in its wake. However conditions were very different to Pakistan and water mixed with grit to cause the Mersey Mole to break down mid-river.
Unable to move backwards or forwards, it led to a dramatic and difficult month-long operation to replace its main 10 tonne bearing.

Some more info and lots of interesting pictures from the construction of the tunnels and the shafts that I haven't seen before here.

Here is a video from the architect, Tom Harker.

Attached Images
Wallasey Tunnel Construction.jpg (195.88 KB, 13 downloads)
Wallasey Tunnel Construction2.jpg (159.68 KB, 13 downloads)
Wallasey Tunnel Construction3.jpg (240.95 KB, 13 downloads)
Last edited by mikeeb; 1st Dec 2021 3:12pm.