Manukau Memorial Gardens embankment works on 10 July 2020

State Highway 20B Early Improvements Project Update

31 July 2020

Kia ora koutou,

State Highway 20B Project Updates keep you up-to-date with project progress and upcoming physical works on State Highway 20B.

Manukau Memorial Gardens embankment under 45 tonnes of aggregate as of 28 July 2020

Transformation

In just a few weeks the road widening construction area outside Manukau Memorial Gardens has been transformed from a steep and boggy hollow (top picture) to a stony mountain (picture above).

To widen the road, an extra lane is being built on top of soft estuarine soil.  In addition to 30,000 tonnes of aggregate used to fill the hollow, an extra 15,000 tonnes of surcharge (weight) has been added to force out the water and consolidate the soft material underneath.

The surcharge will be removed when the ground reaches the right compaction level in about four weeks time.

Resembling little white flags, more than 800 wick drains (five kilometres -worth!) were driven up to 12 metres into the ground by both 30 and 55 tonne specialised wick mandrel rigs.

Wick drains for innovation

The project team looked into how to build the road faster and Wick drains were identified as a key tool to relieve groundwater pressure and speed up the compaction process.

Wick drains are around 10cm wide by 5mm thick and consist of a corrugated plastic strip wrapped in a filter fabric.  They act a bit like a flattened drinking straw.  Pushed deep into the ground, they draw the water upwards when fill (weight) is placed on top.  The water has a shorter drainage path and allows the consolidation to take place in months instead of years.

Bashar Mirza, Fulton Hogan Utilities Senior Project Manager for the SH20B Early Improvements Project

Bashar Mirza, Utilities Manager

Bashar has 27 years of experience in the construction industry in both New Zealand and Australia and also brings in additional six years of construction experience in Iraq and Jordan.

Bashar has overall responsibility for overseeing highly complex service location and relocation.  Focused on improving health, safety and productivity outcomes, Bashar has also improved procedures for locating underground services.  This method has been rolled out across the Fulton Hogan projects, providing a safer, clearer and more efficient process.

“Most people do not notice the work that the Utilities team does because the majority of our work is underground and cannot be seen by the public after the project is completed. However, locating and relocating services is a very complicated job and plays a big part of the project planning and progress.” says Bashar.

“My favourite part of the job is analysing the data captured from the potholing (service investigation) team and trying to find the logic in connecting the alignment of services based on the information provided from the investigation.”

Contact us

Please call us at 0800 796 796 or email sh20B@nzta.govt.nz if you have any questions about the SH20B Early Improvements project.

Project overview

Waka Kotahi NZ Transport Agency and Auckland International Airport Limited are upgrading State Highway 20B for better and more reliable travel options with a new shared path and additional priority lanes between Pukaki Creek Bridge and State Highway 20.

This project will integrate with improved transport facilities within the airport precinct along SH20B and at the upgraded Puhinui Station Interchange.

The project is the first step of the Southwest Gateway programme to provide better public transport, walking and cycling facilities with safer and more efficient freight movements to, from and around Southwest Auckland.

Fulton Hogan undertakes this work on behalf of Waka Kotahi.

Key early improvements on State Highway 20B to be delivered by 2021 include:

• A safe place for people to walk and ride bikes
• Safety improvements including central median barrier protection, improved lighting and a reduced speed
• Improved pavement, drainage and stormwater treatment
• Two improved intersections at Campana Road and Manukau Memorial Gardens.

Waka Kotahi NZ Transport Agency works to create transport solutions for all New Zealanders – from helping new drivers earn their licences, to leading safety campaigns to investing in public transport, state highways and local roads.

For more information on the project, you can also visit our website at www.nzta.govt.nz/projects/southwest-gateway/20connect/