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