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Overview of the under-rail culvert installation

Tru-Line Civil Logo. Brands for New Zealand companies, Greymouth, New Zealand.These culverts are one component of a package of civil works that TruLine is delivering to their client, Hawkins Infrastructure. The Mingha Bluff Realignment is of a section of State Highway 73 within Arthurs Pass National Park between Mingha Bluff and Rough Creek, just to the East of Arthurs Pass village. This is is a narrow, winding section of road that threads through dense mountain beech rainforest. It is a challenging to drive because it consists of two opposing lanes which have a series of very tight blind corners, leading to poor visibility and other objective risks, like narrow sections between steep bluffs and drop-offs. Driving he Mingha Bluff demands high levels of care and attention from all road users.

Road realignment project purpose

State Highway 73 (SH73), or Arthurs Pass, is the primary and most direct transport link between Christchurch and the West Coast. It provides a strategic link not only to the towns of Greymouth, Hokitika and Westport but to the entire West Coast and is therefore an arterial route for tourism as well as basic infrastructure. The Higway also sits within scenic Arthurs Pass National Park and affords easy access to the Park’s myriad alpine natural, historic and scenic short walks and spectacular roadside viewpoints.

Precast Reinforced Concrete Box culverts

Precast concrete box culverts are steel reinforced. There are several accepted ways to install the reinforcement and the overburden appropriately sizes the amount of steel reinforcement needed.

This under-rail box culvert has specific loads associated with this site, the Bealey River bed river-run gravels, and conditions of use in a high rainfall alpine area beneath the Tranzalpine railway. These conditions include burial depth, rail traffic, waterway loading, and impact loadings. The reinforcement in these box culverts is significant and that same reinforcing along with quality concrete and the installation by TruLine Civil ensures at least a 100 year life cycle of service for this valuable component of infrastructure.

Safely documenting civil works photographically


The collegial oversight of the project by the main stakeholders was fine-grained. TruLine’s best practice compliance with rigorous quality assurance standards ensured the job was completed to standard, to budget, and in record time.

My trans-Tasman Workplace Health and Safety qualification, and induction along with the rest of the crew working on each project, plus being kitted out in all the requisite personal safety clothing and equipment ensures that I am able to move around the worksite within safe margins and offer no distractions from the tasks being documented. That said, I am grateful to the TruLine, Hawkins, KiwiRail and Opus personnel for their collegial attitude to my presence on-site during the under-rail box culvert installation at Mingha Bluff.