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Channel Tunnel repair bill puts sprinklers back on the agenda

Heavy costs of repairing fire damage to the Channel Tunnel’s concrete lining have forced Eurotunnel to reconsider the idea of installing sprinklers, the tunnel operator said last week.

Eurotunnel admitted that it was re-examining the possibility of introducing new measures to deal with future fires after last September’s blaze – the third in the Channel Tunnel’s history – seriously damaged its concrete lining (NCE 18 September 2008).

It had previously rejected the use of sprinklers on cost grounds and because of reliability concerns. "Our current system prioritises human life, that’s what the service tunnel [between the two Channel Tunnel running tunnels] is for. But we are also now looking at preserving the infrastructure," said a Eurotunnel spokesman.

The company said installing sprinklers was one of several fire damage limitation options it is investigating. The system under consideration involves the creation of a series of extinguishing stations in the 50.5km long running tunnels. Burning trains would be brought to a halt at one of these stations in the tunnel and once passengers had been evacuated into the service tunnel, high-pressure water or foam would then extinguish the fire.

Eurotunnel would not be drawn on details of the other options under consideration. There are already sprinkler systems inside the enclosed car shuttle carriages which travel between England and France via the tunnel. These are designed to switch on after passengers have been evacuated. Fires are then extinguished by sealing the carriage and releasing halon gas into it.

The tunnel suffered extensive damage after fire broke out in an open sided wagon carrying lorries on 11 September last year. The blaze lasted over 16 hours, causing significant damage to a 650m section of concrete lining. The fire damaged section of the tunnel is not due to reopen until next week, five months after the fire.

The fire has cost Eurotunnel an estimated £180M in lost revenue and £54M in repair costs. A 2006 fire caused minimal damage, but one in November 1996 damaged concrete along 500m of the tunnel and caused £260M in losses. Eurotunnel had previously investigated a sprinkler based fire suppression system in the 1990s but is understood to have ruled it out on cost grounds (NCE 30 October 2008).

A prototype on-board water mist generating system was also examined in the six years after the first tunnel fire. But costs were an issue, a factor highlighted in the Rail Accident Investigation Branch’s (RAIB’s) official report on the 2006 fire. "Fire tests have shown that such a system would suppress the development of a fire for the time taken for the fire fighters to intervene," said the report. "Despite the development of the prototype, Eurotunnel concluded that the system would be unreliable in service, expensive to maintain and would deliver few benefits to the safety of persons."

Eurotunnel is now awaiting the findings of the French Bureau d’Enquêtes sur les Accidents de Transport Terrestre (BEA-TT), which is leading the investigation into last September’s fire with assistance from the RAIB. The company said it would look closely at the BEA-TT recommendations but accepted that more had to be done to limit fire damage.

Eurotunnel engineers said there were concerns about the stability of the tunnel after last September’s fire because of its proximity to geological faults. Before any restoration work could be carried out a team installed rock bolts to mediate the risks of the tunnel collapsing.

Eurotunnel said it hoped to complete all repairs and safety testing so that the tunnel can become fully operational again on the night of 9/10 February. Eurostar is expected to resume its normal service on 23 February.

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