Bridge and Tunnel works to improve resilience and meet freight demands
Rail Upgrade – Northland to Auckland Line

The Northland to Auckland Line Rail upgrade was a $200m government funded initiative that was undertaken in 2020 to improve the resilience of the railway line between Swanson and Whangarei. The project was designed to reduce travel times and to allow for the passage of heavier trains carrying modern “hi-cube” containers.

With freight volumes in Northland expected to increase to 23 million tonnes by 2042, rail is crucial to developing an efficient, integrated transport system for the region. Each tonne of freight carried by rail has 70 per cent fewer emissions than that carried by road.

Selected as one of KiwiRail’s construction partners to deliver this upgrade, United Civil’s initial scope of works included the replacement of two wooden bridges – dating from the early 1900’s – with new two-span reinforced concrete structures. These works were delivered under an Early Contractor Involvement (ECI) arrangement, with United Civil’s engineers working with KiwiRail to develop practical and cost-effective designs for the replacement bridges prior to a construction contract being agreed.

At each bridge, the abutments and central pier were founded on 1067mm diameter steel casings driven to a depth of around 20m and filled with reinforced concrete. The superstructure was made up of 12-post tensioned, precast ballast tray deck units, each weighing around 21 tonnes. The bridge construction scope also included the design and construction of temporary staging, removal of the existing bridges, embankment and stream scour protection works and the placement of ballast to the deck trays.

As part of the wider rail upgrade program, United Civil was engaged by KiwiRail, to assist with the strengthening and enlarging of four rail tunnels along the route. Our scope of services included deformation surveying, removal of track ballast, lowering the tunnel floors, installation of subsurface drainage systems and the import and placement of fresh ballast.

As the various works which formed the Northland to Auckland Line Rail Upgrade all needed to be undertaken under a ‘Block of Line’, time was of the essence and the development and disciplined management of a robust construction programme was essential.

Even though this project had a short timeframe, that was compacted by the Covid-19 lockdown in early 2020, works were successfully completed and the line was reopened on schedule, just four months after works started.

Key features included:

  • ECI Contractor
  • Replacement of two wooden rail bridges, with two-span reinforced bridges.
  • Increasing size of four tunnels, each up to 400m long.
  • Works completed in accelerated timeframes.