The NZ Transport Agency has announced that a new pedestrian and cycle underpass will not be constructed as part of the Baypark to Bayfair Link project (Bay Link).
NZ Transport Agency Senior Project Delivery Manager Andrew Thackwray says evidence gathered as part of the detailed design process has confirmed the construction of an underpass would be highly complex but also identified significant programme and extra contractual costs that exceed the available funding.
“In addition to the costs associated with the physical works, there would also be significant costs due to the additional time needed to build the underpass, and the traffic switches which would be needed to enable construction.
"We understand that this decision will be disappointing for many in the community, but a new underpass is no longer an affordable option in what is currently a highly constrained funding environment.”
Andrew says the total cost to complete the underpass has now been costed at $33 million, and the complexity of the work required would add more than two years to the construction timeline.
“Constructing a new underpass was not just about the tunnel under the highway but the structure also needed to support the massive weight of the bridge approach ramps above it, and the ground below all needed improvement to ensure stability and safety in an earthquake.
“Significant ground improvement works under the box structures are required to support the bridge approach ramps which was different from the assumptions at concept design. The high ground water table at this location would also pose significant challenges.
“The underpass would have had to be built in stages while moving traffic lanes back and forth to keep the busy state highway open to traffic. A complex staging sequence meant construction would have a significant impact on the potential costs and time to build the underpass.”
In November 2018, the Transport Agency announced a scope change to include a new pedestrian and cycle underpass following community feedback at the removal of the existing underpass.
The final costs to build the underpass were to be determined once the detailed design was complete.
“While we anticipated that including an underpass at this stage of the project would be expensive because of its complexity, it became unfeasible when the extra time and very significant cost was added to the existing contract."
Once the Bay Link project is complete, pedestrians and cyclists will be able to cross Maunganui Road using the signalised Bayfair roundabout.
At-grade crossing facilities for pedestrians and cyclists are included as part of the design for the roundabout, and cycle prioritisation through the roundabout will be factored into the phasing of the traffic lights.
The Bay Link project will now return to the original plan, which means the current underpass will close in September 2019 to allow for ground improvement works for the approach ramps to the flyover to be built.
Temporary signalised crossing points will be installed in proximity to the existing underpass on Maunganui Road to provide safe crossing for pedestrians and cyclists.
For more information on the Bay Link project go to www.nzta.govt.nz/baylink