Kia ora and welcome to the October 2017 update from the Transmission Gully team.

Construction update – October 2017

Construction update

Motorscrapers taking a brief stop between works along a section of the new motorway in the Battle Hill Farm Forest Park.

Welcome to October’s construction update for the Transmission Gully project.

The summer season of bulk earthworks is now underway along the 27 kilometre route. With the change of seasons and increasing construction traffic, reduced speed limits continue at all site access-points and construction areas. If you’re travelling through these areas, please take extra care, and obey all temporary traffic signs, they’re there for your safety and the safety of our construction teams.

Here’s the latest from the team on what’s been happening across the Transmission Gully project in the last month, and what’s coming up.

Mackays Crossing

In the northern end of the project, south of Mackays Crossing, ground improvement works for a new 30 metre single span bridge are underway. This involves excavating around 40,000 cubic metres below the footprint of the new bridge. Up to seven metres of liquefaction prone material will be excavated and replaced with more suitable fill, which will increase the resilience of the new bridge during a large seismic event.

Relocation of the main electricity lines at Paekakariki is now complete and “wick drain” installation continues ahead of construction works for this section of the new motorway.  The area to the west of State Highway 1 (around Sang Sue corner) is part of an historic swamp or wetland with weak foundation soils. Vertical wick drains is a ground improvement technique that is being used here, which speeds up soil drainage, greatly improving the time taken to stabilise the road embankment.

Since April last year more than 30,000 wick drains have been installed.

Once the wick drains are installed, this new section of road is pre-loaded with sand from a local store area and is built up to between 2 metres and 4 metres higher than the final road level.  It is then left to settle for 6 to 12 months and constantly monitored to make sure it has stabilised before the final stage of the road construction can start.

Motorists have recently asked about the sealed section of road on the hillside south of Mackays Crossing. Rest assured, this is not a final section of the new motorway – it is part of our main access track, and has been sealed to allow for trucks delivering materials to safely access our site in all weather.

Wainui Saddle

Earthworks continue over the Wainui Saddle, with construction teams working 24 hours a day, seven days a week, in shifts.  The focus of works has been on slope stabilisation and large earth cuts in the hills to make way for the new motorway.

Te Puka and Horokiri streams permanent diversion works continue and are progressing as planned.  Once the upper reaches of the diversion works are complete, construction of the embankments will continue.

Excavation works are ongoing for the permanent Te Puka Stream channel along with excavation and placement of rock in the permanent Horokiri Stream channel.  Bulk earth filling from the Wainui Saddle to the top of the Horokiri Valley has progressed well, allowing permanent stream works in this upper section to now get underway. 

Our environmental team is working alongside construction teams to start works on building a new boulder field for the lizards that were relocated before construction works started.  The lizards, which are being housed at Nga Manu Nature Reserve, will be released back to the newly constructed boulder field in early 2018.

Battle Hill Farm Forest Park

Stabilised earth wall construction is well underway for two of the bridges in the Battle Farm Forest Park area. Foundation improvements are also ongoing. Construction is set to start shortly on another of the bridges in the area, now that the stream realignment is complete.

State Highway 58

At Lanes Flat, construction works continue on the bridges that make up the State Highway 58 Interchange, along with foundation preparations.  Planning to divert the gas main is progressing well and works will start shortly on diverting the gas main to enable State Highway 58 to be realigned.  The Porirua branch water main realignment work is ongoing and is currently making its way towards the recently completed service box culvert.

Work is also nearing completion on the second precast box culvert which will house the Te Marua to Wellington bulk water main. 

Foundation excavation for the Cannons Creek Bridge piers is well advanced. Concrete pours for the northern and southern abutments of the bridge are now complete.

State Highway 1

Great progress continues with earthworks at the southern end of the project.

The Collins Avenue bridge works are progressing well, with a milestone achieved at the end of September – the installation of four large ‘super t’ concrete beams for a section of the new bridge. Watch the timelapse video of the beam installation below.

Construction works continue for the bridges that make up the Kenepuru Interchange alongside State Highway 1, with piling nearly complete and pier and cross head construction now underway.

On Kenepuru Drive, works continue to relocate a trunk sewer main beside the North City TenPin bowling alley.

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A view from above

Check out the project’s image gallery to view the latest photos of the motorway from the air and on the ground.

Visit our video library to see animated videos of the Interchanges and innovative construction works for the project.

Collins Avenue bridge

Aerial view of the super t girders installed for the new section of the Collins Avenue bridge.

Construction update - October 2017

Progress continues at Lanes Flat with the support walls now taking shape for one of the bridges that will make up the new SH58 Interchange.

Girder installation

Night works installation of Collins Ave bridge super t steel girders.

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Keeping you up to date

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