The Northern Corridor and Transmission Gully projects

WSP Opus prepared a business case and served as lead consultant for two key projects that contribute to the Wellington Northern Road of National Significance.

Two key projects for the Wellington Northern Roads of National Significance (RoNS) are the Northern Corridor and Transmission Gully. The Northern Corridor is a 110km link between Wellington Airport and Levin. Transmission Gully is a 27km route through complex terrain.

Northern Corridor

This project will provide a median divided four-lane highway for much of the route. WSP Opus has been involved in the entire project including the business case and economic assessment. We developed smart assessment tools, such as a weekend model for Wellington and the RoNS Economic Modelling Assessment Tool (REMAT). These ensure consistent evaluation and maximum benefits.

Transmission Gully

Our role in the Transmission Gully project was to assess the scheme and design to optimise the 27km route. The project includes three interchanges, a rail crossing and 22 structures.

We prepared a business case to progress this as the first NZTA Public Private Partnership (PPP). We were lead consultant for the Scheme Assessment Report (SAR).Our proactive coordination with other workstreams meant an integrated and streamlined approach.

For the scheme assessment we developed a tool to enable the client to quickly compare options. We worked to understand the issues and developed geometric alignments to minimise impacts on the environment. Innovative use of Google Earth and terrain models saved a lot of time in identifying the best alignments. Extensive geotechnical investigations helped us to design for maximum route security.

The SAR alignment saved $300m on previous concepts, and as a result more has been saved through smart design.