Overview:

This project's contract works involved removing existing ageing timber circa 1900s rail beams and existing sleepers, replacing them with new steel rail beam trusses and new sleepers along the 222m long Taramakau River Rail Bridge (Bridge 13) on the Hokitika Line between Greymouth and Hokitika.

The rail beams and sleepers had to be replaced within a six-week Block of Line (BOL) to align with the annual shutdown of the Hokitika Dairy Plant. This was achieved with days to spare.

Upon completion of the BOL, works progressed to the installation of a new maintenance walkway on both sides of the track on the bridge and level crossing works to raise the road approach levels to match the new higher track height at the bridge's north end. Large client-led variations were also undertaken to perform structural and paint repairs across the bridge by way of general bridge maintenance whilst we were onsite. The repairs, walkway installation and level crossing works were all carried out with careful planning and execution around scheduled train movements along the line.

Scope of Works:

• Establishment onsite, including mobilising site containers, installing temporary 63amp power supply and lifeguard power boxes every 50m across the bridge and temporary air and water supply across the bridge.
• Temporary works including:
  • Erection of scaffolding to undersides and either sides of the rail bridge (providing a platform for the crew to work on)
  • Installation of the gantry crane (designed, built and commissioned in-house). Designed to PS1 and PS2 specifications and design verification report to meet the AS1418 Australian Crane standards. The 8m long bespoke Gantry Crane sat on 4-5T capacity trolleys and is driven by four motors with one controller to allow the gantry crane to move back and forth. The gantry crane also comprises of four 3T winches (allowing for a 12T Safe Working Load lift – the steel truss rail beams are 8.5T being within the weight capacity; the timber rails beams removed are 6.5T in weight capacity
  • Installation of temporary gantry crane running rails (310UC beams), which sat outside the footprint of the old and new bridge rail beams and allowed the gantry crane to access the length of the bridge without compromising the permanent works
  • Erection of high-level scaffolding to undertake high-level paint repairs.
• Removal of old rail beams and sleepers by cutting the beams into 12m long sections held together by the existing sleepers and lifting them off the bridge with the gantry crane
• After removing existing rail beams, the steel transoms that the beams were sat on were cleaned (via jet washing and grinding to remove existing rust) before Brezel Testing the bare steel and finally applying a zinc primer (Carbozinc 858 – 75 microns thick) and two coats of Carboguard 635 paint to 150 microns per layer
• Installation of new steel rail beams by use of the gantry crane lifting beams into place
• Installation of new timber sleepers on top of steel truss rail beams
• KiwiRail track crew then reinstalled the rail tracks
• Surfacing works of the level crossing lifted at the northern end of the bridge
• Removal of gantry crane, including running rails, by use of high rail excavators
• Installation of new maintenance walkway on both sides of the bridge
• Structural and paint repairs
• Removal of scaffolding

• Site clean-up and disestablishment.