27 February 2024

We've been busy!

Happy New Year! We've been busy back at work making good use of the recent sunshine. Find out how we’re installing some of the largest marine bored piles ever to be undertaken in New Zealand on the Wēiti River Bridge, and watch a video showing construction progress to date by clicking here or on the image above. This month we also share some details on how we’re going to construct Duck Creek Road Bridge, which will be New Zealand's longest single span concrete bridge. We also explain more about why we use ‘wick drains,’ the little white flags seen across our construction site.  

Above is a timelapse of the project's current progress to date. Be sure to watch it in high-definition by increasing the video quality to 1080p under the "Settings" button in the bottom right corner.

One of our team members who is 6'1" tall looks tiny compared to the three-metre diameter bridge pile casing.

Forming the foundation for Wēiti River Bridge

Some of the largest marine bored piles ever to be undertaken in New Zealand starts in March.

Two marine piles, each three metres in diameter and 46 metres long, will form the foundation for the western Wēiti River Bridge pier. An 18-metre-long steel casing (like a pipe) will be installed in the top section of the bored hole to protect the sides of the hole, allowing the drill rig to reach the final depth.

Afterwards, three reinforced steel cages will be spliced together, to make a total length of 45 metres and lowered into the hole. Once the cage is in place, 60 truckloads of concrete (or 325.9 cubic metres) will be poured. Then the crews will do this all over again for the next pile. 

This work is expected to take two months to complete.

Image Below: indicative picture of what the steel cage will look like.

The earthworks team have been busy preparing the Duck Creek Road Bridge site for construction.

Duck Creek Road Bridge: New Zealand's longest single-span concrete bridge

The Duck Creek Road Bridge will be New Zealand's longest single span concrete bridge. Once complete, the bridge will be 49 metres long and 12 metres wide, with two traffic lanes and a shared path. 

The bridge will be built by a method known as top down construction. The piles and bridge deck are constructed first, then the earth is excavated from beneath it. 

This will be the first-time pre-cast concrete I-type section beams (girders) are used in New Zealand. They are called NU girders and were developed at Nebraska University in the United States.

Construction progress of the temporary work platform for the Wēiti River Bridge works.

February construction recap

At Top Road, ground works are in progress to create access for the State Highway 1 Bridge works.

At East Coast Road, wick drains (see more about these and why we use them below) and gully drains have been installed as well as putting in environmental controls. The East Coast Road Bridge is progressing well with walls and foundations under construction.

At Ara Wēiti Road, earthworks and ground improvements are continuing. We started construction of two sediment retention ponds. The recent fine weather has allowed crews to make good progress preparing the ground for the future road.

In Stillwater, works are continuing on the temporary work platform for the Wēiti River Bridge. We're also finishing the protection walls to make a safe space for workers to construct the bridge piles. There’s a lot of earthworks being done in this area to make space for the Duck Creek Road Bridge construction. The dirt that was removed from this site has been used to fill a gully further to the west as part of the future road.

In Whangaparāoa, we are getting ready for main earthworks to start in March. To prepare we're fixing the ground, moving a stream and putting in new drainage lines for stormwater.

In the former Cedar Reserve, we're putting pre-load material on the wick drain area to help compact the ground below. We'll soon move the sewer line temporarily. In Archers Block, pest and weed control is being carried out and we'll shortly put in fencing. Later in autumn, we'll start planting in the area.

Mystery solved: the curious white things stuck in sand are called ‘wick drains’ and are a key part of construction process.

What are those? All about ‘wick drains’

Recently we've been getting questions about tiny, white flags stuck in the sand across our construction sites. So, what are they and why do we need them?

The rows of white flags or ‘wicks’ are part of a vertical drainage system. Wick drains speed up the time it takes for water to escape and helps to compact the ground below.

In the photo above, the wicks are sticking out of the sand layer. After the sand layer, a layer of dirt (pre-load) is added on top. You can currently see this at the Whangaparāoa construction site.

Image Below: Illustration showing how wick drains work and the layers in the vertical drainage system.

Locals udderly impressed

Our survey team was recently on site, marking where to put fencing for two new sediment retention ponds. The fencing will keep our curious audience out from where machines will soon be working.

The cattle or "locals" usually do their own thing but this time they noticed the surveyors' amazing work and headed over for a better look - keeping the survey team on their toes!

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

Visit our website www.nzta.govt.nz/penlink.