In April 2017, severe weather caused major slips on State Highway 3 (SH3) through the Manawatū Gorge. This is a major route connecting the Manawatū, Tararua District, Hawke's Bay and northern Wairarapa. The road was closed and traffic was diverted via local roads which are not of State Highway standard, increasing accident risk and travel times. A safe, resilient and efficient replacement road was required.
Our client, Waka Kotahi NZ Transport Agency, proposed a new 11.5km route connecting with State Highway 57 south of Ashhurst and SH3 west of Woodville.
The route presents several challenges: it travels through high-value and sensitive ecological areas, an operating wind farm, and crosses five seismic faults. Minimising impacts on ecology, windfarm operations and maintenance and managing landowner and stakeholder expectations are essential to this project. Together with our Alliance partners Fulton Hogan, HEB Construction and Aurecon, we proposed a route that was partially outside the original Notice of Requirement designation to minimise impact on the ecology of the area, while also avoiding the decommissioning of any wind turbines.
Our team’s design makes the road more resilient during earthquakes and slips, provides ecological enhancements and develops new community facilities. The new road will have a traffic lane and a crawler lane in each direction over most of the route, separated by a median strip and new bridge crossing the Manawatū River. It includes separated walking and cycling facilities.
Our design provides resilience and enhanced life cycle, such as bench cuts specifically designed for the region’s geology to protect against falling rock and debris, geogrids placed under the road at fault locations to prevent sudden splits and drops during seismic events, and structures such as sliding abutments to accommodate fault movements.
Our design also includes enhancement of wetlands and ecological areas and provides a gateway park facility, which enables the community to enjoy and experience the history, culture and beauty of the Manawatū Gorge. A 3D digital model with Virtual Reality goggles allowed our design team to see the project site through the eyes of maintenance workers – to help make working conditions as safe as possible.
We used 3D digital modelling combined with Virtual Reality goggles to showcase various design options during the tender process, allowing the client to experience ‘being’ at the site. Currently our team is working with iwi partners Rangitāne o Manawatū, Rangitāne o Tamaki Nui-a-Rua, Ngāti Kahungunu and Ngāti Raukawa to refine the road’s design. We are also currently carrying out consenting activities and designing enabling works. These enabling works are due to commence in the 2019/20 summer with construction due to begin in the summer of 2020/21.
Our NZ team is providing roading, structural and geotechnical design, drainage design, hydrological modelling, planning and consenting, road lighting and electrical expertise, while our global team's expertise will be called on for specialised disciplines such as special structures and wind modelling.
- 7,600 vehicles used the former SH3 Gorge route daily (on average)
- 11.5km new road
- 13 min travel time (general traffic), 18 mins (freight)