An essential natural waterway linking Slipper and Spectacle Lakes and the Ti Arai Stream in Northland provides a source of native fish for the endangered Tara Iti (or fairy tern).
The existing culvert located under Ti Arai Pt Road became increasingly blocked over time, preventing fish from being able to swim freely up stream. A new purpose-built box culvert was installed to restore the natural flow of the waterway, improve fish passage and support access to this food source.
The culvert replacement centred on the supply and installation of six precast concrete box culvert sections (4.0m x 3.0m x 1.5m) and two wingwall structures. At Hynds, we manufactured these units to tight tolerances and coordinated delivery to align with a highly compressed installation programme, ensuring each section arrived on site ready for immediate placement.
Producing large-scale precast elements of this size requires careful control across casting, curing and finishing to achieve consistency and fit. Equally important was sequencing the units correctly so installation could proceed without delay. We worked closely with the contractor to align delivery sequencing with the installation plan on the ground.
DN Carter Ltd managed transport for the oversized sections using four truck and trailer units supported by pilot vehicles. The first convoy arrived on site at 06:00 on a wet and windy morning, with conditions adding pressure to an already constrained operation. Site access was limited, with no ability for trucks to turn within the work zone, requiring them to reverse out along the access road after unloading. This left little room for error in how units were sequenced and unloaded.
Accurate manufacturing and delivery in the correct sequence enabled a single-day installation, reducing programme risk and minimising disruption. Wharehine Contractors were able to move straight into installation. The first two box culvert sections were in place by 09:30. By 14:00, crews had installed all six sections and both wingwalls.
Read about the wider environmental restoration project at Te Arai here.
From manufacturing through to delivery coordination, we work closely with contractors to help keep complex civil infrastructure projects moving. Contact the Hynds team to discuss your next precast project.
