After extreme rain destroyed a culvert under Great North Road, we designed a new 50 m culvert in parallel with construction to reopen a key West Auckland route.
- Client
- Auckland Council & Fulton Hogan
- Services
- Three waters · Structural · Retaining · Temporary works
- Location
- Great North Road, New Lynn, Auckland
- Scale
- 50 m culvert · 4 m × 2.75 m box · 8 m deep excavations
- Status
- Complete 2018
01 / Project overview
The brief
In March 2017, an extreme rainfall event in West Auckland caused the stormwater culvert beneath Great North Road in New Lynn to fail. Water overflowed onto the road and washed part of it away, private properties were damaged, and a multi-storey building had to be demolished. The affected section of the road was closed for several weeks.
We worked with Auckland Council to design the replacement. The site combined a century-old arch culvert, the Rewarewa Stream, deep excavations beside a major arterial road and pressure to get the road back in service quickly. Construction had to start before the design was finished, so every decision was made against an emergency programme.
02 / Our approach
How we delivered it
A new culvert above the old
We designed a 50 m culvert, including a new 4 m × 2.75 m box culvert built above the existing one, with inlet and outlet walls. The century-old arch culvert below was strengthened.
Retaining and stream protection
Stream-edge retaining walls stabilise the banks at the inlet and outlet. We also coordinated measures to protect the Rewarewa Stream during construction.
Temporary works for deep excavations
Excavations reached up to 8 m deep on a confined site next to the road and the stream. We designed the temporary works that kept them stable and safe throughout construction.
Designing while building
To speed up the emergency response, design and construction ran at the same time with Fulton Hogan. That meant design decisions had to be made quickly and in step with progress on site.
03 / The outcome
“A culvert that failed under a key West Auckland arterial was replaced with a larger, stronger structure, designed side by side with construction to get Great North Road back in service.”
05 / Gallery
■ Similar project?