Project Timeline

We are progressing well and are on track to complete the project by mid-2025:

• July 2024 – Feb 2025 – Complete bridge construction for traffic switch.
• Feb 2025 – Switch single southbound lane onto the new Otaika Bridge.
• April 2025 – Switch both northbound and southbound lanes onto the new Otaika Bridge. Complete northbound works.
• Early-Mid 2025 – Final surfacing, line marking, signage and reinstatement.
• Mid-2025- Project completion.

“The Rainbow Warrior” a 250-ton crawler crane and piling rig in position on the Otaika Bridge Southern Abutment

Progress update

Works on the project continue at pace, and if you drive through the area you’ll notice lots of progress visible from the road. Over the last 3 months the team have been busy preparing to construct Otaika Bridge, completing ground improvement works and constructing retaining walls.

To keep up the great pace, in April, we had 4 piling machines operating at the same time. We have now installed 600 Rammed Aggregate Piers (RAPs) at the Otaika Bridge abutments. Abutments are the structures at the ends of a bridge span that support its structure. See more on RAPs and why we use them in our spotlight section below.

Work on the retaining wall is progressing well, temporary sheet piles were placed in March and the excavation and construction of the piling platform prepared. In April, 50 reinforced 750 millimetre diameter concrete piles were installed along the Otaika Creek, where a 60 metre  by 2 metre high capping beam will be formed - this increases the strength of the foundation before adding in the concrete. Three pours of concrete will be completed by the end of July. 

In early June, we deployed a 250 tonne Crawler crane, known as "The Rainbow Warrior," to start building the southern side of the Otaika Bridge. A 300 tonne crawler was added in early July to service the northern side. These cranes will manage the bridge construction over the next 6 months. The heaviest lift will be about 42 tonnes (about the same weight as 30 cars) for the central bridge span!

At the end of this month, another big milestone will be achieved with the completion of the southern pier and abutment piles for the bridge. The piles are 1500 millimetre diameter, with permanent casings, installed at a depth of 15-22 metres into the bedrock below. The pier piles are out in the Otaika Creek and require temporary staging to enable the 85 tonne piling rig to get into position and drill down. The rock is very hard and requires tools with cutting teeth to grind and break up the rock.

April - Bored reinforced concrete piling along the retaining wall site. 50 750mm diameter piles installed at 12-14m depth

May/June – Reinforcement for the retaining wall completed with 1st pour of 3 sections shown. The capping beam is 2m high x 60 m length. Ground Anchors will be installed through the wall down to bedrock in coming month

What are Rammed Aggregate Piers (RAPs) and why are we using them?

Rammed Aggregate Piers (RAPs) are more efficient and cost effective compared to other piling methods. They require aggregate fill instead of concrete, which is more economical and can be constructed quickly (up to 300 metres a day).

The purpose of the ground improvement work is to reduce settlement under bulk fill loads, improve stability, spreading, and prevent the ground from turning to liquid. The piles transfer loads to the bedrock below and remove or push away weak soils with columns of dense aggregate (minerals or rocks). The dense aggregate pier and the pounding from the moving hammers also strengthens the surrounding soils between the piers.

North Otaika Bridge abutment - Rammed Aggregate Piers (RAPs) being constructed

Ground Improvement – FDP (Full Displacement Piles) at the Northern Tie-in. 200 No. 450mm diameter concrete unreinforced piles at 10-17m depth

Earthworks starting at the Northern Tie-in to construct load transfer platform (high-strength geogrids) over the ground improvement piles

What’s coming up

Over the next 3 months, we plan to:

• Complete the retaining wall ground anchors, followed by backfilling for pavement.
• Finish the Otaika Bridge piling, and reinforced concrete work will continue for piers and bridge ends.
• Landscaping work will commence across the site, including mulch, coconut matting, and planting.
• Start construction of the pavement on the north and south approaches in preparation for kerbing, asphalt and barriers to enable the traffic switches early next year.

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