Josh Irvine

Team Leader - Water
New Zealand

WSP undertook the stormwater and hydraulic design services for the new road alignment and Josh led the design team that delivered solutions for the complex requirements.

Key design challenges included the requirement for a parallel design and consenting process, the proximity of the Te Āpiti wind farm and the steep topography. Innovative design, associated with the nature of the steep terrain and high fill embankments, was required for a number of design elements, including induced trenching and energy dissipation for some culverts.

Overall Josh’s team designed 40 culverts, 30 re-aligned streams and 90 cut-off drains across the project, as part of the wider drainage team.

“This involved ensuring that the deep culverts will withstand the weight of the very high embankments, that water is safely conveyed underneath the highway and will be free of flooding, facilitating fish passage and ensuring streams retain ecological value. This had to be done while minimising any impact on the environment, implementing Te Ao Māori values and working with the other disciplines to resolve potential clashes and integrate the design.”

Meeting these challenges required innovative thinking. Josh says the use of drop structures for culverts, induced trenching and void filled riprap, was particularly pioneering as it’s an uncommon use in New Zealand. This approach resulted in reduced costs, a reduced earthwork footprint and increased ecological and environmental benefits.

A standout of the project for Josh was the experience of working with the people and industry experts within the Alliance.

“The amount of design required for projects of this scale is significant, but with great technical expertise, leadership and collaborative working, projects can be successfully delivered with great community outcomes. The incorporation of Te Ao Māori values into the design process and the visit to the Te Hotu Manawa O Rangitaane O Manawatū Marae as an Alliance was also a unique, enlightening and rewarding experience for me,” he says.