Transmission Gully Motorway

This project involved the building of a 27km link between MacKays Crossing and Linden in Wellington, New Zealand to provide an alternative strategic road link into and out of Wellington. The proposed highway would improve the regional network and provide a more secure route resilient to natural disasters (earthquakes, storms, tsunamis, etc) than the existing coastal highway.

The project was in an extremely environmentally sensitive area. The program and associated estimate needed to be knowledgeable and responsive to the environmental constraints whilst optimising methodology, time and cost.

MIEngineers was commissioned to provide Programming, Constructability, Cost and Risk Services for the project as part of the Phase II Investigations Engineering and Environmental Assessments, in order to assist the team in refining the Preferred Alignment for the route.

MIEngineers developed a Construction Program by preparing a construction staging method and diagrams. For example, materials movement diagrams were used in pricing the significant amount of earthworks for the project (approximately 6,000,000 m3). Overall, this resulted in a better understanding of the constructability issues and aided in the assessment of issues such as mass haul analysis and the location of haul roads and site facilities.

The program included investigation, consent, design and construction components. It also considered “what if” scenarios, risk sensitivity analysis, constructability options, and resource provisions. A Probabilistic Risk Analysis was also undertaken to calculate a P95 value (not to be exceeded value) for the Total Project Cost.

MIEngineers fully met the client’s requirements for the project, receiving consent, statutory approvals and a funding stream.