The River Mersey’s “miracle tunnel” shows origins of our innovation and excellence

Ninety years since opening, the Queensway Tunnel connecting Liverpool and Birkenhead, in northwest England, remains a critical transport link and an enduring example of Mott MacDonald’s ability to push the boundaries of what is technically possible.

When the Queensway Tunnel opened on 18 July 1934 King George V declared it a miracle. At 3.4km it was the world’s longest subaqueous tunnel and the largest municipal engineering project that had ever been undertaken in the UK.

Sequential excavation was used to tunnel through the sandstone underlying the Mersey. The segmental cast iron lining segments was installed two rings at a time. First, segments were installed to support the tunnel crown (the top half), followed by the invert (the lower half).

It was built as the motorcar came of age, to link and improve the flow of people, goods and commerce between the thriving cities of Liverpool and Birkenhead.

In our latest heritage podcast we discover that our founders Basil Mott, David Hay and David Anderson were fundamental to its success, from early feasibility studies through to design and overseeing the complexity of its construction.

Basil Mott was the founding member of Mott, Hay & Anderson, one half of the 1989 merger with Sir Murdoch MacDonald & Partners that created today’s company, Mott MacDonald. Mott first became involved in the project in 1922 when he was asked by Liverpool City Council to bring his experience designing and constructing London’s deep underground railway tunnels and multiple bridges to an important study. The study was to determine whether a bridge or a tunnel was the best option for crossing the Mersey.

Mott worked with two other leading engineers, John Brodie and Sir Maurice Fitzmaurice. They unanimously determined that a tunnel would be cheaper to construct and maintain than a bridge, and provide better connectivity. Design began in 1925 with Mott, Hay & Anderson as engineers.

“The Queensway tunnel was well ahead of its time. The people involved were eminent engineers and forward thinkers. Their work 100 years ago set the standard for tunnelling today,” says Guna Rajadurai, our leader for utility tunnels.

The project pushed the boundaries of engineering design and construction. It pioneered the use of pilot tunnels and sequential excavation to manage the risks of unforeseen changes in ground conditions and ground support; precision drill and blast to achieve rapid progress while minimising the risk of over-excavation and fragmentation in the surrounding rock; advanced grouting techniques to seal water-bearing fissures; and development of a mechanical erector for accurately and rapidly placing the cast iron tunnel lining segments.

“I thank all those who have achieved this miracle. I praise the imagination that foresaw, the minds that planned, the skill that fashioned, the will that drove, and the strong arms that endeavoured in the bringing of this work to completion,” said King George V as he opened the tunnel on 18 July 1934.

The Queensway Tunnel was so successful that three decades later Mott, Hay & Anderson was commissioned to design a second tunnel – the Kingsway, which opened in 1971. Today we continue to support owner and operator Merseytravel, part of the Liverpool City Region Combined Authority, to maintain both of these vital crossings.