Project Spotlight: Te Ara o Te Ata – Mt Messenger Bypass

Mt Messenger Bypass

Downer, HEB Construction, Holmes Consulting, Isthmus, Mt Messenger Bypass, new zealand, Opus, Tonkin + Taylor, Waka Kotahi NZ Transport Agency,


The NZ$280 million Te Ara o Te Ata – Mt Messenger Bypass project is a new 6km highway development project connecting Uruti to Ahititi in Taranaki, New Zealand.

The significant infrastructure development project will replace a winding, accident-prone section of the road, providing a more efficient and safer route for commuters and freight traffic.

Mt Messenger Bypass will ease congestion and ensure smoother traffic flow, supporting regional economic growth and boosting access to essential services. Environmental restoration works will also be implemented to protect local ecosystems.

Major construction works began in October 2022 and are expected to be completed in December 2026.

Mt Messenger Alliance

In April 2017, Mt Messenger Alliance, comprising Waka Kotahi NZ Transport Agency, Downer, HEB Construction, Tonkin & Taylor, Opus International Ltd, Holmes Consulting and Isthmus, was awarded to carry out the design and construction of Mt Messenger Bypass.

Why the Te Ara o Te Ata – Mt Messenger Bypass is needed

Building the Mt Messenger Bypass is required due to the unsafe and unreliable state of the existing road over Mt Messenger. Rockfalls and landslips frequently occur, and repairing the narrow road is difficult.

With about 2,500 vehicles using the narrow tunnel daily, the road no longer meets current traffic needs. Approximately 20% of vehicles using the corridor are heavy vehicles.

Once built, the Mt Messenger Bypass will rise to a maximum of 110 meters above sea level, 65 meters lower than the current route. The old bypass has an incline of 12%, whereas the new bypass will have a maximum grade of 7.5%, resulting in a gentler slope compared to the current road.

The bypass will provide a safer, more reliable route, reducing travel times and improving connectivity between Taranaki and Waikato.

Construction features of Te Ara o Te Ata – Mt Messenger Bypass

The Mt Messenger Bypass is a 6km highway that features:

  • Two bridges of approximately 125m and 30min length
  • A 235m tunnel
  • Environmental restoration works

Construction involves earthworks, tunnelling, and bridge-building, with measures to minimize disruption and protect local ecosystems.

Bridge construction

A 125-meter bridge will carry the road over a stream leading to the Mimi wetlands. This bridge will be a steel box girder structure with a concrete deck sitting on steel pier supports. A temporary staging bridge will be placed to start construction.

A smaller 30m bridge to the tunnel’s north will keep the new route steadily above the valley floor. The bridge and viaduct structures are designed to withstand challenging weather conditions and ensure the safe passage of vehicles.

Road construction

Te Ara o Te Ata—Mt Messenger Bypass will replace a hazardous stretch of State Highway 3 with a safer, more reliable road. The infrastructure project involves navigating rugged terrain in the ‘Mount Messenger Formation’, which consists of sandstone and mudstone. Approximately 1.2 million cubic meters of earth and rock will be moved during construction, with 950,000 m³ reused for fill.

Nineteen rock cuttings ranging from 5m to 60m high will be made. Steel drape mesh will be installed on cuttings above 20 meters to guide rockfall into catch ditches. Soil nails will also be used to stabilize rock faces where needed.

Tunnel construction

The 235-meter tunnel is a significant component of the new bypass. A roadhead machine will excavate the upper position and then the lower section at a rate of up to 3 meters per day in two work shifts.

Permanent rock bolts and steel fibre-reinforced shotcrete will stabilize the tunnel, and synthetic fibres will offer fire protection. Safety features include a public warning system, a fire deluge system, and a safety egress passage. The tunnel will allow wildlife to move easily over the new road, ensuring their safety from traffic.

New Zealand – Major Infrastructure Projects 2024

Challenges of Mt Messenger Bypass

Mt Messenger Bypass requires extensive earthworks and stabilization. It must also carefully manage environmental impact through wildlife underpasses, native planting, and wetland restoration. Unpredictable weather adds further complexity to construction timelines and safety.

Initially estimated at $280 million, the project has already incurred expenses exceeding $172 million, while no kilometre of road has been fully completed. Legal challenges have added $37 million to the 2023-24 construction season alone. This has resulted in significant delays, with construction starting four years later than planned.

Site security measures, including a 1.1 km cableway to transport workers and materials due to rugged terrain, have also increased costs. As of December 2023, over 60% of the original budget had been spent, leading to frustrations among residents who expected the project to be completed and operational by now.

Benefits of Mt Messenger Bypass

The new route for Mt Messenger Bypass reduces the likelihood of accidents and ensures a safer journey. Once the roadway is built, Mt Messenger Bypass will be able to withstand the challenging geographic conditions and weather. It will reduce road closures caused by rockfalls, landslips, and adverse weather, providing consistent access for locals and freight traffic. Motorists will have a smoother drive and ensure that the Mt Messenger Bypass will travel consistently in and out of North Taranaki.

Approximately 60% of the workforce will be either Taranaki locals or people from outside the region who have relocated to live here. The project will create many employment opportunities and provide locals with a variety of training and upskilling opportunities.

Environmental Considerations of Mt Messenger Bypass

Erosion and sediment control are methods to prevent sediment from entering natural waterways. Environmental Engineers have used a combination of erosion control techniques, such as clean water diversions. slit fences, sediment retention ponds and decanting earth bunds to protect the surrounding waterways.

The Mt Messenger Bypass has incorporated wildlife underpasses to ensure safe animal crossings. Over 300,000 native plants will be planted across 47 hectares of land to help restore local ecosystems and stabilize soil.

The Mt Messenger Alliance have collaborated with Tāngata Tiaki to ensure the project adheres to sustainable practices and minimizes environmental impact.

Progress update for the Te Ara o Te Ata – Mt Messenger Bypass project

Construction workers are currently decanting the earth bund, an engineering control that treats dirty water to protect the downstream environment from water quality degradation and sedimentation.

Source: NZ Transport Agency Waka Kotahi

Excavators are working in both directions to improve the habitat of native water species and divert 950m of stream through temporary culverts.

Planting alongside the Mt Messenger Bypass is underway to prevent erosion and filter sediment and nutrients.

Click here to read more about the Te Ara o Te Ata – Mt Messenger Bypass project.

Source: © NZ Transport Agency Waka Kotahi 2024

Source: © Infrastructure Partnerships Australia 2024

Image Source: © Infrastructure Partnerships Australia 2024

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