FEARS OF a Mont Blanc type fire in Liverpool's Mersey Tunnels have prompted construction of three new escape cross passages in the Kingsway Mersey Tunnel. Work is due to start within weeks.
Tunnel operator Merseytravel has awarded specialist tunnelling contractor Amco Donelon the £2.2M contract to build the three 3.3m diameter cross passages between the twin bores of the tunnel.
Originally built between 1966 and 1973, the bores are 17m apart but only have cross passages at each portal.
The new passages will allow motorists to escape from one bore to the other in the event of a fire.
The Mont Blanc tunnel fire in 1999 killed over 40 people and prompted a general review of safety procedures in tunnels.
This led to the decision to build the new Mersey cross passage fire escape routes.
Mott MacDonald is consultant for the project, which will be carried out under the Engineering Construction Contract target cost form.
Amco Donelon won the job after coming up with an imaginative scheme which allows work to be carried out at night, limiting traffic disruption Horizontal boreholes will be driven along the length of the three cross passage bores.
Ground conditions are expected to be Middle Bunter Sandstone, some of which is heavily fissured along the route of the tunnels.
Cross passage location has been chosen to coincide with areas where the rock is less fissured.
After drilling, the boreholes will be pressure grouted to stabilise the ground and to keep out groundwater.
The tunnels will be bored using a Brokk excavating machine which will also place lining segments. These will then be covered with in situ fibrereinforced concrete to give a robust low maintenance structure.
Work is expected to start early in the New Year and finish by summer 2002.
The project team would not comment in advance of an official announcement by client Merseytravel next week.
INFOPLUS For more on tunnel fires go to www. nceplus. co. uk