Take a look at Hamilton's new $166 million bridge

A $166.6 million bridge across the Waikato River at the southern edge of Hamilton, linking the city to a new subdivision, is weeks away from opening.

It is hoped the four-lane bridge, a striking feat of engineering on the city landscape, will open to traffic in August when it will be officially named.

The bridge is being paid for with the government's Housing Infrastructure Fund and connects the city ring road Wairere Drive and the main arterial route Cobham Drive to Peacockes Road through the new Southern Links transport project.

The entire project is made up of a $180.3m interest-free loan to Hamilton City Council from central government and $110.1m in subsidies from NZ Transport Agency / Waka Kotahi.

The interest-free loan was part of a billion-dollar fund up for grabs in 2016 to deliver housing outcomes.

Council infrastructure and assets general manager Andrew Parsons said overall the project was ahead of the government's schedule by almost a full year.

Parsons said bulk funding helped avert some delays caused by border closures during Covid-19, including by allowing all the steel - about $5m worth - to be procured from overseas at once.

The steel was then sent to the country's two largest fabricators in Whangārei and Hawke's Bay, where work continued uninterrupted by the Auckland and Waikato lockdown in late 2021, which lasted between three and four months.

The bridge features two extra lanes than usual, for vehicles with more than one passenger, crash barriers next to the road, wide footpaths on either side which connect to Te Awa Cycle Trail, and a balustrade which gives a view of the Waikato River 36m below.

The balustrade, underside and a pedestrian bridge above, are all constructed with Cor-Ten steel - an atmospheric corrosion resistant steel which ironically looks like rust.

Parsons said Cor-Ten steel was chosen for its protective coating which would deepen in colour as it weathers, because it required no maintenance - usually a large ongoing cost of infrastructure.

Each pile on the main bridge is 1.3m in diameter and drill down into the ground below sea level, while the four girders are 4m deep each and weigh 100 tonnes per metre.

"To build a structure like this, you actually rely on the capability and the resources of a country. The scale, just in the structure itself, I'm happy to be proven wrong, but I suspect it's probably one of the more significant structures taken on in recent decades."

The girders were made by Eastbridge in the Hawke's Bay and feature 50mm thick steel and ribs welded inside at close spacing.

"Each weld - to get enough heat into the weld when you are dealing with 50mm thick steel - the whole girder shrinks ever so slightly, so as you repeat all these welds, and you've got four girders, you want all the shrinkages to be the same.

"So it requires a very skilled operator, so when you bring everything to site, it's the right length."

The bridge's piers do not disrupt the Waikato River, with the central pier sitting on a river beach that was previously inaccessible to the public because it was private land.

That pier's lattice work was designed to represent the woven basket or kete used to catch eels at that location.

"That steel work is so massive that if you were to lie it down on it's side, a shipping container is the height of those members.

"Each half weighs between 240 and 260 tonnes. Even though everything looks thin and slender and elegant, they are really quite massive structures."

The Cor-Ten used on the pedestrian bridge 6m above the traffic bridge is curved and shaped to look like a waka, with two 25m tall masts known as taurapa capping the concrete foundations.

The masts represent a waharoa for river crossing and were inspired by traditional waka taurapa, the carved canoe stern piece.

Consultants BBO and Edwards White Architects designed the traffic bridge which also features seating for cyclists and pedestrians, while PFS Engineering - all from Hamilton - fabricated the pedestrian bridge in sections at nearby premises.

The 71m-long footbridge, made to resemble Tainui's waka, was then "stitched together" into a single piece on site before the 87-tonne bridge was lifted into place.

Māori designs adorn both bridges and make up part of a network of cultural expression and symbolism across the Peacocke infrastructure projects, delivered in partnership with the Southern Links Tangata Whenua Working Group (TWWG).

The $135m contract to build the traffic bridge, a pedestrian bridge and surrounding roads was awarded to Heb Construction in August 2020 with work getting underway in November that year.

Parsons said the project was initially scheduled for completion late last year but Covid-19 and severe weather made that impossible, though council was still on track to deliver the project ahead of the government's schedule.

Since the contract was awarded, the council had approved an increase of $26.6m, including $24.5m for inflation and $2.1m because of costs associated with Covid-19.

Another $5m of additional works was also approved to be fully funded by developers.

The northern portion of Peacockes Road, 1.3km, would open at the same time as the bridge, with the date to be confirmed in the next few weeks.

The southern end, 1km, was being delivered separately, by a different contractor as part of an east-west road known as Whatukooruru Drive and would be completed late next year.

Meanwhile, stage 1 of the new Peacocke subdivision - which is set to have 8000 homes - was well underway and stage 2 already had some consents granted.

rnz.co.nz

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