Construction of the Queensway Mersey Tunnel
Caulking cast iron lining with lead wire 1930. Archive reference 6788-122
Basil Mott, who had a mining background, was appointed tunnel engineer in chief. Construction began on 16 December 1925 when Princess Mary set the pneumatic drills in motion to dig the first shaft in a surviving portion of the Old George’s Dock at the Pier Head. It was from here on the Liverpool side, that two pilot tunnels, one above the other, were excavated beneath the river, with similar excavations being made from the Birkenhead side at Morpeth Branch Dock, eventually to meet in the centre.
The photograph at the top of the previous page of tunnel workers at the Rendel Street heading in Birkenhead in 1928 shows an example of the hewn rock and what the tunnel looked like during excavation; although this is a portion of the branch tunnel on the Birkenhead side rather than the under river section but similar in appearance.
Excavation was made using a combination of drilling and explosives. During the height of the tunnel construction 1,700 men were employed directly on it. Seventeen men lost their lives.
Queensway Mersey Tunnel construction, showing the suspended tempoary roadway, 1931. Archive reference 6788-262
On 3 April 1928 the pilot tunnels had been driven through and official parities from both sides of the River shook hands beneath the Mersey, clad in oilskins. There was very little divergence in the meeting of the headings, for the most part 2.5 cm (1 inch) or less; a testimony to the accuracy of the survey work.
The pilot tunnels were enlarged into the dimensions of the full-sized tunnel. The circular underwater section is 13.41 metres (44 foot) in diameter and the top half was worked first as a precaution against collapse. Cast iron segments were placed in freshly excavated sections to create a support lining and throughout the length of the tunnel. Gaps at the back, between the cast iron and the rock were fused with grout to make the tunnel water-tight; additionally bolts were sealed with special washers and gaps between the adjacent cast iron segments were sealed with lead wire (for the latter process see above image, reference 6788-122).
Queensway Mersey Tunnel, concrete filling in 44 foot tunnel, 1931. Archive reference 6788-343
The lower pilot hole served as a conduit via a wagon railway to remove spoil and bring in materials. Once the top half of the tunnel was completed a conduit was still required and a temporary roadway was constructed and suspended from the upper tunnel (see above image, reference 6788-262); the cast iron supporting lining segments are visible in this image. Much of the spoil from the tunnel excavation was tipped up-river at Dingle and formed the foundations of ‘Otterspool’, a riverside promenade and gardens for the public.
The under river tunnel roadway was supported on continuous concrete walls parallel to the length of the tunnel which left convenient gaps; those at the side were to be used for air-ducts. There are four traffic lanes, two in each direction. There were also two branch tunnels either side of the River to serve the docks.
Gaps in the cast iron lining were filled with concrete as a further watertight measure, as you can see in image reference 6788-343. Finishing and sealing coats were later added.
Georges Dock Ventilation and Control Station Pier Head with Liverpool Overhead Railway 1936. Archive reference 12740-1
It was realised that ventilation of the tunnel had not been adequately taken into account and a complex system was put in place, requiring the construction of six tunnel ventilation buildings, three on either side of the river, to house the huge fans which connect to the tunnel, forcing fresh air in and taking foul air out.
The ventilation buildings were designed by the tunnel architect Herbert J Rowse; angular block formations with square towers in streamlined Art Deco style. The tower shown in this final photograph from1936 is also the tunnel control centre and is faced in Portland stone. Rowse also designed the four tunnel entrances, the tunnel interior, the toll booths and lighting columns.