The long road to a new tunnel

The long road to a new tunnel

The Government has finally announced the next steps towards a new Mt Victoria tunnel.  Jane O’Loughlin reports.

The city has embarked down the long road to a new tunnel, with a decision by Transport Minister Chris Bishop to green light the next stage of work on State Highway 1 improvements around the Basin Reserve.

Drilling will start soon in the Town Belt as part of geotechnical investigations.  However the tunnel, estimated to cost between $2.9 and $3.8 billion, will be many years away, with construction not starting in earnest until at least 2028.

Minister Bishop announced last month that the NZTA Board had endorsed the investment case along with $185m to progress design, consenting, and early works development.

The State Highway 1 improvements package includes the construction of a second Terrace Tunnel, a second Mt Victoria Tunnel, and a major roading upgrade at the Basin Reserve.

Upgrades to the Basin Reserve including grade separation for state highway and local road traffic. This will allow state highway traffic to travel directly from Mount Victoria Tunnel to the Arras Tunnel.

NZTA said ‘pre-implementation’ work would involve property acquisitions, geotechnical investigations, further design work, and securing consents.

Some road improvements, housing removal/demolition, and site clearance may also start to occur.

Engagement with affected landowners was to start immediately, however this appeared to take the Wellington City Council by surprise.

Councillor Geordie Rogers wrote to residents’ associations in Mt Victoria, Mt Cook and the inner city on Labour weekend to warn them that NZTA had started sending letters to property owners they had identified as being "affected" by the development of the second tunnel.

The letter advises the property owners that NZTA may wish to purchase their property to complete the project.

“Please know that despite WCC Councillors and Senior Staff working openly with NZTA the Transport Authority did not give us a heads up that they were sending letters out. “Our staff have made it clear to NZTA that we don’t see this way of working as acceptable and are also requesting NZTA to urgently provide a briefing for City Councillors.”

As reported previously in The Local, NZTA already owns 12 properties in Mt Victoria, on Paterson, Austin and Brougham Streets.  It’s not clear whether it would need to acquire more on this side of the tunnel.

Also likely to be controversial is the recommendation by NZTA that the tunnel be tolled. The decision will be made once construction timing and funding is confirmed and will be subject to consultation and Government approval.

Once constructed, the tunnel would have a 3.6 metre shared path for walking and cycling, replacing the existing narrow pathway.

Among the various benefits listed is improved travel times for the number 2 and Airport Express buses – if rerouted through the new tunnel instead of through Mt Victoria’s streets and the existing bus tunnel.

The project is now in the pre-implementation stage, which is expected to take approximately 3 years. During this stage, NZTA will continue to develop project designs, further investigate options for tolling, purchase the property required for construction and secure any necessary consents and approvals through the Fast-track Approvals Act (2024).

November will see geotechnical investigations by NZTA contractors get underway.

This involves drilling five boreholes and collecting core samples from four geotechnical investigation locations in the Wellington Town Belt to provide an understanding of the local subsurface conditions.

The boreholes will be between 40m and 80m in depth. NZTA says it expects to find silty soils, overlaying in situ Rakaia terrane sandstone and mudstone (locally known as Wellington greywacke).

“Taking soil and rock samples is fundamental in geotechnical investigations because it provides direct, physical evidence of subsurface conditions. This is essential for identifying rock strength, joints and faults, then planning the tunnel alignment and retaining structures.”

According to NZTA, two drill rigs will work in parallel to minimise the duration of disruption. Investigation works will require the temporary closure of some sections of track in the Hataitai Park area of the Wellington Town Belt. Track signage will be put in place.

One of the types of rigs is shown in the image.