31 October 2023

O Mahurangi – Penlink Main Construction Underway

October 2023 is a milestone for the project with the start of main construction works. This earthworks season, we plan to move 400,000 cubic metres of earth while also managing erosion and sediment controls.

Construction of the temporary staging/platform on the western side of Wēiti River is also underway. This platform will enable us to build the Wēiti River Bridge. Noise will be heard on both sides of the river during this work. Work is also well underway in Whangaparāoa where the highway will connect to Whangaparāoa Road.

We appreciate your patience as some work will impact our neighbours and road users.

Tree clearing progress looking towards Whangaparāoa Road.

Oketopa | October Construction Updates

Our main construction phase is officially underway! The main construction phase will last until the end of the project. Here's what we've been up to this month: 

State Highway 1/East Coast Road

• Top Road site entrance widened to allow the safe entry and exit of construction vehicles. This means we don’t need to use access from SH1, reducing the impact on other road users.
• Line marking and installation of temporary barriers on a section of East Coast Road. Please take care when travelling through our temporary traffic management.
• Work undertaken to allow for the relocation of services on East Coast Road.

Ara Wēiti Road

• Continued earthworks in the pine forest area for the new road.
• Constructed environmental controls and sediment retention ponds.
• Began ground improvement work - read more later in this newsletter.
• Began ecology work and tree clearing in Fill 17. Fill 17 is a 50,000 cubic metre fill located directly west of Bridge 5 (check out the zones map below).
• Continued construction of the new main project office for all staff.

Stillwater

• Works are underway for the Wēiti River Bridge temporary staging and scheduled to be completed in early 2024.
• Continued tree clearing prior to bird nesting season.
• Continued construction of access tracks and environmental controls.
• Gully drains installed in earthworks areas.
• Earthworks commenced.

Whangaparāoa

• Continued tree clearing works.
• Constructed access tracks and erosion and sediment controls as works progress west towards the Wēiti River.
• Continued ecological investigations in the area.

Check out more progress photos on our website.

Solid Foundations for Success

We are carrying out ground improvements and other improvements across the project to create stable and durable foundations. A stable, durable foundation is necessary for the success of the new highway and bridges. Some of the different improvements being used are: 

Shear Barrette's will be used for the State Highway 1 Bridge. They are narrow concrete walls that are used to transfer load from a weaker part of a structure to a stronger part.

Reinforced concrete piles are used at the western abutment of the Wēiti River Bridge. The piles come in 1200mm and 900mm diameter sizes and are put into several rows to form an underground wall. This underground wall provides a stable platform on the existing sloping ground for the bridge abutment.

Wick drains (pictured below) are vertical drainage systems that serve as an escape route for water during soil compression. Wick drains reduce the time it takes for water to escape, speeding up water removal from silt and decreasing settlement time.

Gully drains are both perpendicular and parallel to the general gully alignment. The design allows any water to escape when fill material goes above the gully drains.

Drainage blankets go beneath fill embankments, often above gully drains or high fills. They help water escape from beneath the fill, ensuring no water accumulates and weakens the ground.

Counterfort drains address areas where there is evidence of subsurface water. These drains are 500mm wide and vary from 3-6m deep. They intersect broken zones in the soil structure, offering a way for trapped water to escape.

The success of the project depends on the stability and durability of its foundation. The above improvements ensure the new highway withstands the test of time.

Diagram below shows how wick drains remove the water content from soft soils.

Community drop-in session at the Hibiscus Coast RSA on Saturday 30 September.

September Drop-In Sessions Recap

Thanks to all who attended our drop-in sessions last month at the Manly Bowling Club and Hibiscus Coast RSA. We received a variety of feedback but there were a few themes more common than others, including:

Tolling

There will be two toll points along the 7km route so you pay the right amount for your journey. The toll points will be at the State Highway 1 interchange and east of the Wēiti River Bridge. A free route will be available for all road users. More tolling information is available on our website.

Future-Proofing

O Mahurangi - Penlink will be two-lanes as our traffic modelling shows this is appropriate for the amount of traffic that will travel along it and the entire route is future-proofed. Our traffic modelling extends to 2048 and takes into consideration future growth.

This means that when demand is met, the route is wide enough to accommodate two general traffic lanes and two bus shoulder lanes, plus a separate walking and cycling path. The new highway will have an 80km speed limit and no passing lanes. If a vehicle were to break down, there is enough room for the vehicle to move over and allow traffic to pass.

Whangaparāoa Intersection Design

Peak-hour Whangaparāoa Road traffic would challenge the efficiency of a roundabout because they work best when traffic volumes are balanced from all directions. There is also a need to keep Whangaparāoa Road as a key local route, including public transport connections to local shops and schools. Signalised intersections also provide safer access for pedestrians and cyclists. In this case, a signalised intersection is the best solution.

North-Facing Ramps at State Highway 1

Our traffic modelling shows the primary demand for O Mahurangi - Penlink is between Whangaparāoa and Auckland to the south. The design is future-proofed to allow the addition of north-facing ramps at the SH1 intersection.

Whangaparāoa Traffic Impacts During Construction

The majority of the new road is being built "offline" to minimise disruptions to Whangaparāoa. Some impacts are expected when transporting goods to site and later when connecting the new road to existing infrastructure. We will carefully manage traffic impacts when we ‘tie-in’ to Whangaparāoa Road from 2025. If you live in the project area and would like to receive work notifications, click here to sign up.

Whakapā Mai | Contact Us

For more information on the O Mahurangi - Penlink project, call us on 0800 7365 465 or email us at omahurangi@nzta.govt.nz.

Visit our website: www.nzta.govt/penlink