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Keeping the Waterview Tunnel fire protected

FireNZ Magazine, September 2017

Tunnel boring machine working on the Waterview Tunnel.Tunnel boring machine working on the Waterview Tunnel.

 

On 11 August, the NZ Transport Agency (NZTA) issued a media release advising motorists that the northbound Waterview Tunnel would be closed for three nights the following week for scheduled maintenance work. The northbound tunnel was closed from 10pm to 5am on Monday 14th, Tuesday 15th, and Wednesday 16th of August, with motorists taking detour routes.

 

It was the first maintenance closure since the tunnels opened at the beginning of July, and is the first in what will be a three-monthly schedule of full closures.

“We’ll be checking and testing the electronic equipment like the smoke detectors, fire hydrants and deluge systems, which are required as part of the manufacturer’s guarantees and the building code,” said Brett Gliddon, NZTA’s System Design Manager. “… ongoing maintenance is really important to keep the tunnel operating safely and efficiently.”

So, what exactly does it take to keep the tunnel operating safely, and what fire systems and maintenance and testing schedules are in place to ensure that the tunnel is kept fire-free?

 

Big construction numbers

The 2.4km Waterview Tunnel opened on 02 July, having cost $1.4b to build and having created more than 18,000 jobs during its construction period. The first vehicle travelled through the tunnel five years after construction first began.

The twin-tunnels are the longest road tunnels in New Zealand – the Lyttleton road tunnel at 1.97km previously held the record. At 13.1 metres in diameter, each able to accommodate three lanes, the tunnels reach a maximum depth of 45 metres as they wind their way between Pt Chevalier and Mt Roskill.

It is said to represent the biggest change in travel patterns since the opening of the Auckland Harbour Bridge in 1959.

Fitting out the tunnel involved some big numbers: 74,500 cubic metres of aggregate, almost 5kms of drainage pipes, 140,000 square metres of paint, 4,000 lights, 62 ventilation fans, 50kms of cable trays to support wiring and other equipment, and 400kms or 270 tons of cabling and wiring.

The tunnel boring machine, specifically designed for the Waterview geology by the German company Herrenkencht and manufactured in their factory in the southern Chinese province of Guangdong, was a staggering 87 metres long.

The Waterview Connection was delivered by the Well-Connected Alliance, made up of the NZTA, Fletcher Construction, McConnell Dowell, WSP, Beca Infrastructure, Tonkin+Taylor and Obayashi Corporation.  Sub-alliance partners are Auckland-based Wilson Tunnelling and Spanish tunnel controls specialists SICE.

 

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Tunnel safety

The Well-Connected Alliance is responsible for operating and maintaining the tunnel and interchange for the next 10 years as the Waterview Tunnel Joint Operation (WTJO). Working with the NZTA/Auckland Transport (AT) Auckland Transport Operations Centre (ATOC), the WTJO manages the tunnel as part of the wider Auckland motorway network. 

Management of the tunnel operation tools and traffic is carried out from ATOC’s 24/7 control room located at Smales Farm, Takapuna.

According to NZTA, the tunnel is equipped with state of the art communication and safety features that include electronic message boards, public address and radio sound systems, CCTV cameras and high-powered ventilation and fire sprinkler systems. Heat sensors help to detect smoke or flames, and lighting inside the tunnel changes according to weather conditions.

There are emergency exits and telephones at 150 metre intervals along the right-hand side of each tunnel providing direct access between the tunnels for use only in emergencies.

Any vehicle stopped in a lane from accident or breakdown will be pushed or towed to a place of safety as quickly as possible, with on-ramp signals helping to regulate traffic flow.  Over-height detection systems warn over-height vehicles and provide drivers an opportunity to pull over and take an alternative route.

 

Fire systems

According to an Australasian Fire Authorities Council (AFAC) Fire Safety Guidelines document, incidents such as the 1999 Mont Blanc tunnel fire highlight the “consequences of not incorporating appropriate fire and emergency management into tunnel procedures and ensuring their continual review and upgrade.”

In that incident, thirty-five people died in a fire that, stated the Guardian, “turned a stretch of the Mont Blanc road tunnel between France and Italy into a furnace.” At one point, temperatures reached 1,000 degrees Celsius along a 650-metre section of the 11.6km tunnel. Parts of the tunnel's concrete lining collapsed under the intense heat, exposing a fragile layer of crumbling rock.

There was no fire protection or sprinkler system, and only limited, outdated ventilation and smoke extraction. Fire fighters who arrived on the scene within minutes of the blaze were trapped by smoke for days and had to be pulled out through an underground ventilation shaft. One died and more than 30 hospitalised.

According to Manchester University’s School of Mechanical, Aerospace and Civil Engineering, the fire highlighted the dangers of smoke in an enclosed area without an adequate smoke extraction system. These dangers included obscurity, which may prevent people from fleeing due to lack of visibility, and temperature and toxicity, “which incapacitate the mobility of people and may be fatal.”

According to the AFAC guide, suppression systems need to be able to control a growing fire, allowing safe evacuation and giving firefighters the opportunity to get close to the seat of the fire for control and extinguishment. The system should also “minimise the adverse effects of fire within the tunnel, providing more time for motorists to evacuate, maintain structural protection and lessen the risk of prolonged business interruption due to spread of fire.”

A smoke management system must be able to minimise the impact of smoke upon occupants as they evacuate the tunnel and upon emergency services personnel as they enter it to engage in firefighting and rescue activities.

According to the NZTA, in addition to a smoke management system, the Waterview Tunnel’s fire detection and suppression systems are comprised of the following:

  • Fibre optic based linear heat detection system
  • Redundant Fire Alarm Panels
  • 173 deluge zones (30 metres long)
  • Fire hydrants every 50 metres
  • Five 250 cubic metre water tanks containing enough water to supply three deluge zones and the tunnel’s fire hydrants in case of fire
  • Fire pumps to ensure water pressure in hydrants and deluge zones
  • Smoke detection in all cross passages and all ventilation buildings
  • Sprinkler system in common areas in all ventilation buildings
  • Gas suppression in all equipment rooms inside the building
  • Hydrocarbon detection on all sumps
  • Foam suppression system on all sumps to prevent hydrocarbon fires
  • Fire traps in drainage system to prevent spread of the fire

Testing schedules are complex and varied. Most work, says the NZTA, is carried out on a one-monthly, three-monthly, yearly and two-yearly schedule.  However, sections of the less frequent schedules are carried out every month to space the work load out and ensure there’s not one significant body of work to do at the end of a cycle. In a nutshell, these include:

  • Main Fire Alarm Panel – smoke detectors, warning signals, power supplies, sensors, fire brigade and ATOC fire signals – third party certification is two-yearly.
  • Building Fire Protections System for the Northbound and Southbound Vent Buildings – sprinkler system, power supplies, sensors, alerting devices, gas flood system, smoke detectors, warning and evacuation signs, gas piping – full end-to-end testing of sprinkler system with third party sign-off and certificate is two-yearly.
  • Tunnel Fire Detection System including Alarm boards, sensors and LHD is monthly. 
  • Tunnel Deluge System and Water Supply including Deluge Valves, Sensors, Support Structures, Water Supply Tanks, Pipes, Level Sensors, Pumps, Guages – third-party certification is two-yearly.
  • Back Flow Preventers are checked yearly.
  • Foam Suppression System in Hydro Carbon Traps undergo monthly, yearly, five-yearly and ten-yearly checks.
  • Fire Hydrants and Booster System are checked monthly, yearly and five-yearly.
  • Portable Fire Extinguishers are checked monthly, with pressure testing or replacement every five years.

This all puts the three-evening maintenance closures each three-months into perspective. A minor, scheduled inconvenience to motorists to ensure the safety of what is proving to be a very popular and successful piece of critical national infrastructure.

 

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