Ready to launch: Transmission Gully's mega bridge set to move

Sunday, 30 September 2018

Construction of the pier foundations for the Cannons Creek Bridge continues at pace with a number of concrete pours happening through January 2018.

Transmission Gully's biggest bridge is approaching its launch date.

The spans of the 226-metre-long Cannons Creek Bridge will soon be pushed across the gorge it traverses and onto piers currently being completed.

Standing 60m above the ground below, the bridge was a showcase of technical design, according to New Zealand Transport Agency spokesman Chris Hunt.

An artist's impression of the Cannons Creek bridge looking south towards Wellington.

Not only did it have to look good, it had to be able to withstand a 1-in-2500 year seismic event, he said.

**READ MORE:

An aerial view showing the launch pad in relation to the gully to be spanned.

* Transmission Gully looks to be user pays

* Transmission Gully project hits halfway mark

It will take four stages to launch the bridge over the gorge.

* Aerial photographs show motorway progress**

Described as one of the most technically challenging roading projects ever seen in New Zealand, work on the 27 kilometre, $850 million motorway north of Wellington started in 2014.

A 220-tonne crawler crane works on the foundations for two 20-metre-high piers to support the Cannons Creek Bridge.

Scheduled to be completed in April 2020, it will link to the $630 million Kāpiti expressway which, in turn, joins the $330m Peka Peka to Ōtaki Expressway.

When completed, the four-lane Cannons Creek bridge would include a total of 44 steel girders, each 1.8m wide and 3m deep, to make up the framework of the bridge deck, supported by two abutments and two piers.

Works on the project will start to become visible to the public in coming months.

Photos from last month show work ramping up on the project, expected to open in 2020.

Large culverts like this one for the Wainui Stream are significant structures that will be largely hidden once the road is complete.

More than 10,000 cubic metres of concrete would be used to build the bridge and its components; equivalent to more than four 2m-deep Olympic-sized swimming pools. The entire four-phase launching process was expected to take about 10 months.

Structural works, including construction of major intersections, were the focus of recent work on the project, Wellington Gateway Partnership spokesman Sergio Mejia said

'Works are increasingly visible to motorists, and in the coming period will require traffic switches on the adjoining state highway network to ensure safe working areas for construction.'

Good weather over the coming season would see the project's bulk earthwork and construction of the final road surfacing layers completed,

'After this, the bulk of the planting will be completed and the project moves into the final phases of road construction and completion works.'

As work ramped up to meet the 2020 completion date, motorists could expect traffic switches in both north and south areas of the project.

In the south, southbound traffic between the Mungavin Interchange and Linden would move to newly constructed outer lanes while traffic heading north would temporarily use a brand new slip road near Paekākāriki .

This week, weather permitting, contractors would be make changes at the Paekākāriki end, near the project's site entrance, to prepare for the switch.