Today we announced that the Transmission Gully motorway is now scheduled to open to traffic by September 2021.

Bridge under construction over a gully.

The largest structure in the Transmission Gully Project – the 230m long, 60m high bridge over Cannons Creek, looking west towards Porirua, July 2020.

While any delay is disappointing, we’re pleased that we are able to provide you with certainty that the road is scheduled to open in just over a year.

Transmission Gully is a highly complex project being built on 27km of very difficult terrain. The construction is now approximately 85% complete. However the Covid-19 stand down period and subsequent work restrictions have caused much longer delays than the five weeks of Alert Level 4, due to the loss of valuable summer construction time and other factors.

Our winter works programme has enabled us to source and bring onto site critical materials to allow the project to progress through the winter construction season. If materials, such as aggregate, were not sourced during winter, the materials may not have been available later in the season and this could have caused further delays to the project’s completion. The aggregate is trucked overnight to maintain safety along the busy SH58 - thanks again to residents for their ongoing patiience.

The Covid-19 disruptions to our schedule, coupled with the uncertainty about future potential disruptions, has required a change to the methods the project team is employing to complete the road construction. This will see us using more local subcontractors and resources, and a change to the type of pavement that the motorway will be finished with.

A ‘deep lift’ asphalt pavement (also known as structural asphalt) will be used in areas approaching and over the Wainui saddle, and on other sections of the motorway with steep gradients. The earthworks on these sections of the motorway account for the majority of the remaining pre-pavement work yet to be carried out on the project, where work has been significantly impacted by the five-week Covid-19 stand down and associated disruptions.

The ‘deep lift’ asphalt pavement being used is much more resilient to poor weather during construction, meaning that work can continue to be carried out during marginal winter conditions, bringing the new completion date forward by an estimated four months relative to what would otherwise have been possible.

The current Level 2 restrictions are not having a significant impact on construction. Changes have been made to work practices in line with Alert Level 2 requirements, but work is continuing to progress well with up to 420 people working onsite at the moment.

With just over a year to go until the road opens to traffic, you’ll start to see even more of the road taking shape in our regular updates.