Below Rail Infrastructure, Engineering, Environment and Sustainability, Freight Rail

Kaimai Tunnel works well underway

Kaimai Tunnel location. Graphic: Google

A multi-million dollar upgrade of New Zealand’s longest rail tunnel is well underway.

NZ rail operator and manager KiwiRail says the team repairing and upgrading the 8.8km Kaimai Tunnel, on the North Island, has gotten off to a good start.

Project manager Neil Mason and construction manager Tevita Brugger told the media last week that teams have already completed repairs on more than 300 metres of concrete slab and completed cleaning on 5.1km tunnel.

A project to upgrade and repair the tunnel, which sees roughly three-dozen freight rail movements a day, was announced in October 2014.

KiwiRail said the primary goal was to refurbish the rail track and tunnel floor to meet a forecasted growth in freight volumes and axle loads.

Brugger said the material developed to undertake repairs is very special because it is strong enough to run trains on after 90 minutes, is not flammable and does not give off any harmful gasses.

“We still have 350 metres of concrete to do and expect to have it finished by Christmas,” Brugger said.

“The project work is starting to show some effect.

“As a direct result of the work that has been done the line returned to its 80km/h speed for the first time in four years.”

Over a two-day closure in September, the repair team installed a special slot drain into the floor of the tunnel.

“The drain will be used to intercept water running underneath the tunnel,” Brugger explained.

“These water volumes were encountered when the tunnel was built but are not well understood.

“We need to control the water and to do this we need to determine the size of the pipe. The slot drain will allow us to observe the water flowing freely.

“Next year, we’ll start construction on the new leaky feeder radio system followed by a new phone system.”

Brugger said further investigation was needed into the flow of water in and around the tunnel.

The research would help determine the scope of the project, which could take up to 10 years, and cost as much as $50 million.

“Most projects would involve 5-6 days of work on-site per week, whereas we only have access to the tunnel once a week and the rest of the time it remains open, due to high volumes of trains,” Brugger continued.

“On top of that, we are working in a 9km-long tunnel with a single track, with crews who do not live around the area.

“Kaimai is a complex and challenging project and this means that to maximise our production time requires a higher degree of planning and coordination is required.”