At Hundalee, wave action was eroding the foreshore directly adjacent to KiwiRail’s South Island railway. It posed a serious threat to the foundation of the railway track. The project team installed Bluemont Rock Bags™ and large Timaru Basalt rock as the rail erosion control measure, stabilising the coastal margin and safeguarding the track corridor.
Project Snapshot
Location: Hundalee, South Island, New Zealand
Client: KiwiRail
Application: Coastal rail erosion protection
Total Material: 4t2W Bluemont Rock Bags™ and large Timaru Basalt rocks
Project Overview
KiwiRail runs freight and passengers the full length of the South Island’s east coast – Invercargill in the South to Picton in the North. It’s a long route, and for much of it, the track sits right beside the water. No buffer. That kind of exposure makes rail erosion control an ongoing operational priority, and Hundalee is one of the places where wave action posed a serious risk.
The Challenge
A railway is only as good as the ground it runs on. At Hundalee, the foreshore was eroding – close enough to the track that it wasn’t a future problem, it was a current one. Without action, continued wave action would have undermined the formation, put rail safety at risk, and interrupted freight and passenger services on one of the South Island’s most important corridors.
The Solution
The project team chose a layered approach to protect the coastal rail corridor and reinstate the culvert headwall. Timaru Basalt boulders formed the lower layers, absorbing direct wave impact and providing a heavy, stable base. Bluemont Rock Bags™, also known as Kyowa Filter Units, went in above the culvert headwall.
Installation
The team filled the Bluemont Rock Bags™ with rock sourced from Kaikoura. Timaru Basalt boulders, used for the large rock layer, had to be sourced by train. Two layers of Timaru Basalt formed the base, with Bluemont Rock Bags™ stacked on top to reinstate the upper section above the culvert headwall. Their flexible, contained form allowed them to stack securely, conform to the structure, and hold firm against long-term wave action.
Results
After installation, the Bluemont Rock Bags™ delivered effective armour protection to the Hundalee foreshore, stabilising the coastal margin and reducing wave erosion risk to the railway formation. The completed works provided a durable protective layer of rail erosion control well suited to the demands of an active coastal environment.
Related Applications
Bluemont Rock Bags™ are used across a range of erosion and scour protection projects – riverbank stabilisation, bridge scour protection, and infrastructure corridors exposed to wave action or hydraulic conditions.
Contact us to learn more, we are here to help resolve all types of erosion issues. You can also call +61 2 9091 0360 or email info@rockbags.com.au for Australian-based projects, or info@rockbags.nz if you are based in New Zealand.
