Wick drain installation north of Otaika Bridge

What we have been up to on Stage 2

A lot has happened in the months since the project kicked off.  The team have made great progress and there has been lots of changes to see. 

The team began construction in March setting up the work site and implementing temporary speed limits between the Loop Road roundabout and Portland Road, and they shifted traffic eastward to provide a safe working space, including guard-rails, line marking and signage.

Long term environmental controls have been set-up, temporary drainage culverts and subsoils, overhead and underground services relocated, and vegetation clearance has been completed.

The temporary Oaks Road entrance has been built and traffic diverted onto this new alignment mid-May.  The team have also completed site investigations across the project area, such as boreholes (this involves coring out earth to see the different layers and materials), which helps us to understand the ground conditions better so we can make sure the road is built on top of the strongest material.

Over 3,200m3 of drainage metal has been placed for the wick drain blanket, and the team have installed 35,000Lm of vertical wick drains across the project area.  Wick drains provide drainage paths to remove water out of the ground so it compresses and strengthens faster.

To monitor this process, there is a lot of preload instrumentation needed i.e., settlement plates, markers, profilometers, vibrating wire piezometers and the team undertake regular surveys to monitor settlement.

Construction has started for the piling platforms of the north and south abutments for the drilled displacement piles (DDP) operation (read more about this further along in this update) at the Otaika Creek bridge.

‘Riprap’ on the southern bank of Otaika Stream

What’s coming up (July to September)

Over the next few months work will continue into winter where the new bridge over Otaika Creek will be built.  The team will complete the ‘riprap’ erosion scour protection for Stage 1 of the northern bridge abutment. 

‘Riprap’ is a permanent layer of large angular rock material used to prevent erosion in areas with concentrated water flow (Otaika Creek in this instance). The bulk fill of northern bridge will also be completed ahead of the DDP piles.

The large piles that will be installed at the approaches of the bridge will soon be made using 2,500m3 of concrete. Over 460 of these piles are needed to make up the north and south approaches.

After the DDP piling the team will start temporary staging for the bridge, and then commence construction of 1500 permanent bridge piles, and the adjacent bridge abutments.

In late September they will establish traffic management for the southern tie-in towards Portland Road and start excavation of the northern tie-in to roundabout for piling platforms and more DDP piling.

Project Engineer Lance on site.

Meet our Project Engineer Lance

Over the course of the project, we will profile different members of the team.  This month we will hear from Lance Vazey – Oxcon CLL Project Engineer.

Who you are and what your role is on the project?

I am the Project Engineer for the civil construction elements of the project.  I oversee vegetation clearance, temporary sediment controls, bulk earthworks, temporary works piling platforms, crane pads and haul roads, wick drain installation, preload instrumentation install and monitoring, stormwater swales, roading pavement subgrade, streetlighting and services, line marking and roading elements, such as kerbs, channels, islands, signage, guardrail safety barriers and wire-rope install, and landscaping to name a few.  I am also responsible for overseeing the site traffic management implementation, onsite stakeholder liaison, quality management and the health and safety onsite.

What is the most exciting aspect of this project?

The most exciting aspect of this project is taking on the challenge of a high profile multi-disciplined project on SH1 which has been a long-time in the making with a tough public perception to turnaround to a positive story. We have a high performing team, with a fast-paced programme to deliver a quality product for the road users and stakeholders. 

How do you see it benefiting the road users and community?

I see the huge amounts of heavy haulage travelling this road every day, this project provides a much safer route by separating the northbound and southbound lanes by a grade change, better road surface and structures so my family and friends can travel to and from Te Tai Tokerau safely.

What do you like to do in your spare time?

Hanging out with my young family on the Tutukaka Coastline and enjoy smoking meats low and slow over the charcoals.

Fun fact about Lance

My wife and I spent almost 2 years living and working in France and can (somewhat) speak, read and write in French.

Click the image above to watch a video about the drilled displacement piling process.

Drilled displacement piling (DDP) explained

You may have seen a large piling rig set up at the Otaika Bridge over the last few weeks.  This big piece of kit (75tonne drill rig) will drive approximately 445 displacement piles at the bridge, before moving to work near the roundabout.

A drilled displacement pile (DDP) is different from conventional piling, where instead of excavating the soil, the DDP method compacts the ground around the pile.  The auger (drill bit) progresses through the ground pushing the existing soil outward.  When the auger has reached the bottom of the pile, concrete is introduced. 

The auger is then back spun and retracted from the ground in a controlled fashion ensuring constant positive pressure from the concrete pump, so that the pile hole diameter is maintained.  The result is a concreted pile shaft with the surrounding soil being densified by the displaced soil.  This ground improvement piling technique densifies the surrounding ground and can help to prevent liquefaction during an earthquake event.

Our drill rig will drive an auger to depths ranging from 13 to 17 metres to create a 600mm diameter concrete pile. Some piles will be reinforced by plunging a cage into the wet concrete after the drilling and concreting process is completed.

Click the link below to watch a video explaining the process. This isn't our project, but it gives an overview of the process.

Watch the video.

100-year-old orange tree going to its new home

100 year orange tree

Recently, the team worked with a project neighbour to carefully excavate and load out what is believed to be a 100-year-old orange tree. The tree was planted circa 1890 and supposedly early clippings from the tree were used to establish Kerikeri’s Orange tree nursery. The tree was originally planned to be removed, with the road widening.  Instead, the orange tree was carefully removed being mindful not to disturb the roots, loaded onto a truck and gifted to the tree owner’s neighbour.

Project timeline

Please note the below construction timeline is a guide only and may change slightly with weather and other potential disruptions. We’ll keep you updated with any changes to the construction timeline.

• Feb 2023 – site preparations start
• March – September 2023 - ground strengthening (this is called ‘preloading’ and works by slowly compressing the ground surface to create a stronger foundation for holding the road and vehicles).
• March - April 2023 - temporary Oaks Road realignment (permanent open March 2024)
• Sept – October 2023 - installation of drainage pipes and culverts for stormwater, new streetlighting and utility services and construction of new concrete shared path
• Sept – Mar 2024 – bridge and retaining wall construction
• Mar – May 2024 – pavement, line marking, barriers
• June 2024 - approximate construction completion.

Investigation works for the piling on the Otaika Bridge.

Sealing the entrance to entrance to temporary Oaks Road.

More information

For more information on the SH1 Loop Road improvements, contact us at northlandproject@nzta.govt.nz

Visit our website www.nzta.govt.nz/loop-road