Project Spotlight: O Mahurangi – Penlink

New Zealand

Auckland, Aurecon, fulton hogan, GHD, HEB Construction, new zealand, O Mahurangi Penlink, Tonkin + Taylor, Waka Kotahi NZ Transport Agency,

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O Mahurangi – Penlink is an infrastructure development designed to cross over East Coast Road and connect to State Highway 1 (SH1) with a new interchange in North Auckland, New Zealand.

The $830 million infrastructure project will deliver a new 7km two-lane highway, a bridge over the Weiti River, and a shared path for pedestrians and cyclists.

Penlink will provide a faster and more direct route for commuters, reducing travel times and easing congestion. It will enhance transportation options and stimulate economic growth in the northern region of Auckland.

Early works started in January 2023, and main construction works started in October 2023. The overall construction is expected to be completed in 2026.

Waka Kotahi NZ Transport Agency appointed GHD as the Principal Technical Advisor for O Mahurangi—Penlink. GHD developed the preliminary design and helped Waka Kotahi throughout the procurement process.

Penlink’s construction contract was awarded to HEB, Fulton Hogan, Aurecon and Tonkin + Taylor Alliance.

The key features of the O Mahurangi – Penlink project involves:

  • A 7km two-lane road
  • A shared walking and cycling path that runs separately from the roadway
  • A 540m long, 45m high bridge over the Weiti River that accommodates a separated shared path for walking and cycling. The bridge will be marked for two lanes but wide enough for a third lane to be used for ‘tidal flow’ purposes
  • An overpass over State Highway 1
  • South-facing ramps leading to State Highway 1
  • Local road connections at Whangaparāoa Road, Stillwater Township, and East Coast Road
  • Widening Whangaparaoa Road to four lanes from Brightside Road to Arklow Lane
  • Realignment of East Coast Road joining the new road with the Redvale Interchange

O Mahurangi Penlink at the construction starting line

Wēiti River Bridge

The Wēiti River Bridge will be an extradosed bridge, meaning it will be a hybrid between a box girder and a cable-stayed bridge design.

The box girder element means it can carry a range of services and utilities to the Peninsula, such as power and water. The cables will allow for a longer bridge span and reduce the number of piers needed to support it.

Construction crews updated the Wēiti River Bridge design to deliver more benefits. This includes:

  • Reducing the number of piers from three to two and remove the centre pier to allow clear passed through the navigation channel
  • Removing the pier on the eastern bank of the river to avoid cliff face excavation
  • Minimising greenhouse gas emissions to improve construction methodologies
  • Decreasing materials to reduce construction emissions

The New Zealand Government is funding the planning and construction of O Mahurangi – Penlink through the New Zealand Upgrade Programme (NZUP).

O Mahurangi – Penlink has been designed as a toll road to cover construction and maintenance costs and reduce taxpayers’ financial burden. This will ensure that the project’s ongoing expenses are not funded through general taxation.

Tolls will also help manage traffic flow and reduce congestion by encouraging drivers to choose alternative routes or travel times.

One of Penlink’s primary challenges is the engineering complexities involved in constructing the infrastructure in a geographically challenging area. This includes the construction of bridges and roads across varied terrains and under varying weather conditions, which can complicate construction schedules and techniques.

Another challenge is managing the environmental impact associated with large-scale construction, especially the Wēiti River and the surrounding ecosystems. Careful planning and environmental protection measures are required to ensure construction activities do not affect local flora and fauna.

O Mahurangi – Penlink is expected to create approximately $150 million in Auckland’s local and regional economy. Approximately 3870 local jobs will be created during and after construction.

Once the project opens to traffic, it will improve travel times between the Whangaparāoa Peninsula and Auckland. Engineering crews also used advanced safety designs throughout construction to minimise road accidents, improve road safety, and decrease congestion.

Improved accuracy of roads will also support growth in the Silverdale and Milldale communities. It is expected to attract more investment, increase commercial activity, and provide more employment opportunities.

Several environmental considerations were taken into place for O Mahurangi – Penlink.

One major focus is preserving Wēiti River’s health. Environmental Engineers implemented erosion and sediment techniques and water quality monitoring to prevent pollution and maintain the river’s water quality.

Engineers helped protect and manage the local wildlife habitats. Replanting native vegetation and creating wildlife crossings will ensure habitat continuity and safe animal migration paths.

Breaking ground on a ground-breaking venture for Penlink

Erosion and sediment controls were implemented to reduce environmental impacts on waterways near the Penlink construction site. Every work zone has specifically designed controls approved by Auckland Council. Ongoing monitoring is still being taken to protect both freshwater and marine environments.

Engineers also utilised noise barriers and modern construction techniques to reduce the acoustic impact on nearby residential areas.

Groundworks are underway to facilitate access to the SH1 bridge. Sediment retention ponds are being constructed to accompany ongoing earthworks and ground improvements.

Video source: Waka Kotahi NZ Transport Agency via YouTube

Main earthworks have begun at the Whangaparāoa site, with ground fixes, stream relocation, and new stormwater drainage installations currently taking place.

O Mahurangi Penlink is set to become a crucial transport connection in north Auckland, serving the growing needs of Silverdale, Whangaparāoa, and the Hibiscus Coast.

Source: © NZ Transport Agency Waka Kotahi 2024

Image Source: © NZ Transport Agency Waka Kotahi 2024

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