The project

Tonkin & Taylor (T+T) is a member of the Mt Messenger Alliance, which is working on the bypass of the Mt Messenger section of State Highway 3 and involves the construction of 6 km of new road, including bridging and tunnelling. The existing road had lead to a number of fatalities and serious crashes over recent years.

Approximately 32 hectares of indigenous vegetation and 3.5 km of stream length will be affected, and significant earthworks are proposed within an environment with geotechnical challenges.

Because of the significant ecological effects of any works in this area, the project was made an ecological project first and foremost, and a transport project second. As a result, the work will result in net biodiversity gains within 15 years.

The Project team has also completed an innovative slope stabilisation solution at Te Ore Ore Slip on SH4 in parallel.

Local Procurement

Using local and iwi affiliated businesses and contractors is a priority for this project, and the well-drilling and earthworks contractors used are from the area.

This allows the local community to benefit from local work and spend in their area, as well as having the opportunity to build capability by being involved in a project of national significance.

Material Requirement Reduction

To allow us to minimise earthworks, and enable steeper slope angles, GRP (Glass Reinforced Polymer) Bars are being used in temporary support cases. The reduces steel requirements and helps to keep the project clearance footprints as small as possible.

Geotechnical Sustainability

The design team focussed on minimising the vegetation clearance footprint through developing a strong understanding of the geotechnical stability environment.

This includes:

• Optimising the road alignment to sit low and less steep, meaning environmental disturbance was decreased. This means less ecological disruption, less vegetation clearance, and less excavation required – preserving delicate soil ecosystems!
• Preparing an array of possible designs, meant that there was preparedness to adapt in changing circumstances throughout the design process.
• A cableway was built to transport people and materials in and out of the remote construction points, which has sustainability benefits over using traditional access tracks, which would have negative ecological impacts within areas of high ecological significance. The cableway was made feasible through anchor designs that were small footprint, but robust.
• Specifying low maintenance, high quality solutions. This minimises future energy consumption, waste, time, and costs associated with maintenance work.

Cultural Presence on Site

Iwi contribution is paramount in this project. Early on, the The Alliance committed to a reaching a voluntary agreement with Mana Whenua (Ngāti Tama) to secure land for the project. The proposal put forward was approved by the iwi, with over 80% of their members voting in favour of selling the land for the project. Subsequently, Ngāti Tama representatives were invited to the project Board and management team, embedding the cultural lens to decision making.

Additionally, proactive cultural monitoring underpins construction, with Tanga Tiaki (cultural monitors) having a continuous physical presence to oversee and advise on aspects such as the treatment of land, tapu (sacred) trees, heritage artefacts, and any erosion or sediment which impacted waterways.