On the evening of Thursday 27th June we enjoyed an excellent tour of the Queensway (Birkenhead) Road tunnel.
The Queensway tunnel was opened in 1934 and was at that time the world’s longest road tunnel. It is 2.1 miles long and 45ft (14m) in diameter. The tunnel carries 4 lanes of traffic on a single level and originally had 2 side exits, 1 each end leading to the docks. The Wirral end side exit leading to the Birkenhead docks is visible in the tunnel but no longer in use.
Currently on average 95,000 vehicles per day travel along the Birkenhead tunnel.
The air handling system is most impressive, at the time of construction the adverse effect of Carbon Monoxide fumes was know but not well understood. As the result the designers took a very conservative approach to the Air handling system design (with some suggestion that it was over engineered). We were able to see one of the 5 fan stations. Each fan station consists of 4 fans (2 fresh air and 2 exhaust), these fans are 28ft (8.5m) in diameter and weight 25Tonnes. They rotate at 75rpm and can move 0.5Million cubic feet (14k m3 of air per minute!!!). We were able to see one of these giant fans start up, a most impressive sight.
The tour included to old Engineering control room. This was recently decommissioned and replaced by a state of the art Control Room. This is responsible for the control of both Mersey (Birkenhead and Wallesey) Tunnels and also combines Engineering staff and Police. The room has access to 850 cameras. Most services are duplicated e.g. power is supplied form both ends of the tunnel so a power cut at one end will not affect the tunnel operation.
A little known fact about the Birkenhead tunnel is that it was originally planned to have 2 tram lines beneath the road deck. These lines were never laid and the area is now used for Utilities. We were able to go underneath the road deck in order to see some of the Civil Engineering involved in the Tunnel. One of the most impressive features of the tunnel is how dry it is. We walked in the (Fresh) air plenum where we were able to feel the fresh air flow for ourselves.
The tour concluded with a visit to one of the 7 refuge areas where users of the tunnel could go in the event of an emergency. These are located below the road. Each refuge can hold approximately 80 people and has a video connection directly to the control room. The refuges are linked via a walkway (again below the road deck level) so people can easily be evacuated in either direction to avoid the hazard. Happily, to date these refuges have only been used for exercises.
Overall an extremely interesting and informative visit. A big thanks for Phil and Ryan, our excellent tour guides.