RIGOUROUS EMERGENCY procedures last week prevented a major construction fire in the A86 motorway tunnel near Paris from turning into a tragedy.
Nineteen site workers avoided suffocation in the fire by sheltering in the Herrenknecht earth pressure balance shield tunnel boring machine (TBM), which has a 10 hour oxygen supply.
Fire broke out at the northern end of the A86 tunnel, 1.4km from the entrance and 600m from the TBM at around 10pm on 5 March.
It is thought the blaze was triggered by a fire in a construction transporter vehicle. No-one was killed, and one fire fighter was taken to hospital suffering from smoke inhalation.
A Paris fire brigade spokesman said the blaze took three hours 39 minutes to get under control, although it took firefighters around 18 hours to fully extinguish the blaze and five hours to rescue all 19 trapped workers.
The 10km A86 tunnel running south from Rueil Malmaison to Pont Colbert, south west of central Paris is privately funded.
Toll road operator Cofiroute is responsible for the £1bn design build finance and operate project.
Contracting consortium Socatop comprising contractors Vinci, Eiffage and Colas is carrying out construction work.
When complete the 11m diameter single bore tunnel will operate as a two level structure with the top level running on a slab constructed across the tunnel bore's mid point. Each level will carry traffic running in a single direction.
Construction of the median slab is following behind the tunnel boring operation. The fire broke out on the tunnel floor under the median slab, so fire fighters used the upper gallery to bypass the blaze and reach the workers sheltering in the TBM.
Firefighters then gave them breathing apparatus before leading them to safety.
The fire brigade spokesman said that tunnel workers sheltered in the machine, as stipulated in the tunnel's emergency plan.
He added that Socatop had held fire drills in the tunnel in November and January. Another was scheduled for next week.
As well as having an oxygen supply the TBM was equipped with sprinkler supplied with water from outside the tunnel.