Deluge to fight fires in Lyttelton Tunnel
The coolest thing about the $29 million upgrade to Lyttelton Tunnel in Christchurch is the firefighting deluge system. It delivers 10 litres of water per minute per square metre from 2460 nozzles. It’s fed by a newly built 1.5 million litre reservoir – and a good example of applied science.
The heavy mist isn’t enough to knock down a person, but they’d probably wish for a ‘‘wetsuit and snorkel’’, said NZ Transportation
Agency tunnel manager Barry Stratton during a late-night test of the deluge system last week.
The deluge system is divided into 63 zones, three of which can be operated at any one time.
A fire in the tunnel is likely to start in a relatively small location – a single vehicle accident, for example – rather than stretching the whole 1944 metres of the tunnel.
But having three working zones means NZTA can deal with a multi-vehicle pile-up or more than one fire.
The deluge is designed to contain a fire until Fire and Emergency NZ (Fenz) can arrive, said Chris Collins, NZTA’s tunnel upgrade manager.
Fenz will enter the tunnel, rescue people and put out the fire.
In a fire, tunnels can act like chimneys – quickly drawing smoke and toxic fumes away from the fire and sending it rushing down the tunnel.
This happened during the infamous 1999 Mont Blanc tunnel fire, in which 39 people died. That fire burned for 53 hours and reached temperatures of 1000 degrees Celsius, being fed
initially by margarine and later by petrol and other combustibles. That tunnel is 11.6km long.
The Lyttelton deluge comes out of three pipes – one in the centre of the tunnel ceiling and two at the ceiling corners.
As part of the upgrade, 16 new hi-tech cameras have also been installed. These can turn, pan, tilt, zoom, and take high resolution video. They are operated 24 hours a day from the tunnel control room on the Christchurch city side of the tunnel through the Port Hills.
They pick up anomalies in the tunnel – whether pedestrians, fallen objects, stopped vehicles or smoke. No-one on a Lime scooter has attempted the tunnel, Stratton said. Bikes are banned.
There’s also a heat detection strip in the ceiling which runs the tunnel length.
If tunnel operators are somehow not paying attention, the computer can trigger a deluge.
Operators aren’t supposed to be distracted but during the February 2011 earthquake the tunnel control building was smashed by boulders and operators evacuated.
That building, designed by famed architect Peter Beaven, was demolished and replaced by a workman-like new structure.
Speakers in the tunnel allow operators to communicate with those in the tunnel, including telling them in which direction to evacuate.
The tunnel is curved and exits are not always visible.
There have been fires in the tunnel in the past, including an incident where a tarp was ignited by an exhaust pipe.
Opened in 1964, the Lyttelton road tunnel (there’s also a rail tunnel) was the longest in the country until the $1.4 billion Waterview Tunnel in Auckland opened in July 2017.
As a new project, Waterview got similar safety features from the start. Lyttleton was an upgrade and will be complete in a few months.
About 10,500 vehicles use the Canterbury tunnel each day.
When the road between Sumner and Lyttelton re-opens later this year, dangerous cargoes will be sent onto that route rather than through the tunnel. The road was closed by rockfall during the quakes.
‘‘We hope to never use [the deluge] in anger,’’ said Collins.