Access to the Dublin Port Tunnel will have to be carefully controlled to avoid a fire disaster because the ventilation system is not adequate to cope with congested traffic, a traffic management report to be published next week reveals. Frank McDonald, Environment Editor, reports
The report, which is to be published by Dublin City Council, will outline a strategy to manage heavy goods vehicles (HGVs).It is also expected to show that the €650 million tunnel will not bring as much relief to the Liffey quays from traffic congestion as was anticipated.
Mr Michael Egan, spokesman for the National Roads Authority, told The Irish Times yesterday that it would have cost an extra €100 million to install a more sophisticated smoke extraction system that would work even in bumper-to-bumper traffic.
"A tunnel that's 4.5 kilometres long is going to be a hostile environment anyway. The last thing you want is people stuck in traffic because a fire in that situation would create panic with the potential for significant loss of life."
It is understood that Dublin City Council's project engineers advised that a smoke extraction system be installed, rather than leaving it to the ventilators to "push" the smoke out. But this was ruled out by the National Roads Authority on cost grounds.
The project was designed before the two most recent fire disasters in the Alpine tunnels of Mont Blanc and St Gotthard, in 2000 and 2001 respectively, which led to a review of international best practice to avoid "worst case scenarios".
"No matter how good the ventilation system is, if a tunnel is chock-a-block with traffic, there's the possibility of a major disaster," said Mr Egan.
"But the port tunnel has cross passages between the two tubes as a means of escape."
Because a smoke extraction system has not been installed, access to the twin-tube tunnel will have to be controlled at each end to ensure free-flowing traffic at all times. This could lead to significant tailbacks at the two portals, off East Wall Road and on the M1 motorway.
However, Mr Egan said the National Roads Authority was "absolutely satisfied" that the project "meets best international practice".
He stressed this meant that "there has to be a high level of certainty at all times that traffic entering the tunnel can get out at speed".
Spending an additional €100 million to further enhance ventilation would not necessarily have produced a better result, he said.
"We do not believe that safety has been compromised in normal traffic movement."
The draft traffic management plan being finalised by the city council will provide for full closure, partial closure and regulated entry at each end in order to keep traffic moving at free flow along the tunnel's four-lane dual-carriageway.
One of the principal aims of the plan is to maximise the use of the tunnel by HGVs, particularly to relieve the Liffey quays.
But even apart from the controversy over its height, there is doubt about what proportion of these heavy goods vehicles will actually use it. "We probably gilded the lily a bit," one insider source conceded yesterday.
"The situation is more complex than it was presented," he said. "It's probably fair to say that we inadvertently oversold the benefits." The draft management strategy attempts to quantify the number of HGVs, with destinations in the inner city, for which the quays would be more convenient than the tunnel, but it still forecasts that a "significant" proportion will use the tunnel.
Meanwhile, tunnel project managers, Kellogg Brown and Root - a subsidiary of Halliburton, the US military's biggest contractor - is under investigation for overcharging by more than $16 million for meals served to US troops in Iraq.