New rail bypass to eliminate oldest tunnel on Picton to Christchurch railway line

Thursday, 19 December 2019

KiwiRail is undertaking a $35m project to shift a section of railway between Christchurch and Picton.

A section of the railway between Picton and Christchurch is being realigned in order to bypass an old tunnel.

KiwiRail is undertaking a $35 million project to shift a 1km section of track on the Main North Line to eliminate the tunnel at Tar Barrel south of Ward.

The project is part of the Kaikōura Earthquake recovery works and is expected to take 18 months to complete.

KiwiRail chief operating officer for capital projects David Gordon said the tunnel lining was damaged during the earthquake. It had been repaired but a lot of work was still needed to bring it up to modern standards, which would cause considerable disruption.

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Vehicles will be moved onto a temporary diversion at the site next week to allow continued two-way traffic on State Highway One through this area while the overpass is built.

* $40m for Coastal Pacific as first post-quake service marked in Kaikōura

* Picton to Christchurch railway line reopens for freight**

500,000 cubic meter of earth will be removed in this project but will not leave the site, the same earth will be reassigned for landscaping purposes.

'Its small size means trains must slow down to go through it, which lengthens journey times on the line and causes operational constraints,' Gordon said.

The Main North Line and State Highway SH1 between Christchurch and Picton were critical elements of New Zealand's land transport networks.

'Bypassing the tunnel, which runs below SH1, allows us to improve rail operations and seismic resilience for both road and rail,' he said.

The small and curved tunnel was a safety risk for fast moving trains as trains had to slow down to 25kmh to go through the tunnel. Once work is finished trains will be able to travel up to 80kmh through the area.

The Tar Barrel tunnel (Tunnel 21) was built in 1913. The 167m long tunnel is the oldest in the Main North Line.

'Currently, around 36 train services travel along this section of the Main North Line each week,' Gordon said.

KiwiRail is working with Waka Kotahi NZ Transport Agency to deliver these works. The project is expected to take about 18 months to complete.

The new alignment involves moving one kilometre of track through a cutting that required builders to move about 500,000 cubic metres of earth.

KiwiRail is working with NZTA to eliminate the uses of this 106-year-old tunnel, the project was started in July this year and is expected to take about 18 months to complete.

There are 'up to seven excavators, four compactors, three bulldozers, six dump trucks, one piling drill rig, one crane and traffic control equipment,' being used on the site at the moment. However, during periods of heavy rain, the works will stop due to safety reasons.

A new road overpass will be built over the railway south of the tunnel.

Vehicles will be moved onto a temporary diversion at the site this week to allow for the continued two-way traffic on SH1 through the area while the overpass was built.

The dirt would not be taken off-site, instead it would be placed within the premises and would be later used for landscaping purposes. Two hectares of native plants is being planned at the site.

'The programme will cost slightly over $35 million with currently 60 people working on site, and that will increase to 80 people,' Gordon said.

There were 'up to seven excavators, four compactors, three bulldozers, six dump trucks, one piling drill rig, one crane and traffic control equipment,' being used on the site, he said.

The Picton to Christchurch 335-kilometre train trip, includes 22 tunnels and 175 bridges.

Last November, Prime Minister Jacinda Ardern announced that the KiwiRail's Coastal Pacific passengers service would get a $40 million investment and would make it a year-round service.