Hataitai Bus Tunnel, Wellington

Date: November 2014-May 2015

Client: Wellington City Council

Consultant: Opus International Consultants

Contractor: BBR Contech

The Hataitai Bus Tunnel was opened in 1907 to connect the expanding suburbs of Kilbirnie and Hataitai to Wellington city.

BBR Contech were engaged by the Wellington City Council to undertake strengthening to the portal walls with work commencing in November 2014.  The work scope included:

  • Installation of 30-no. double-corrosion-protected (DCP) production anchors utilising 32mm and 40mm Macalloy stress bar.  Anchor installation included high-pressure post-grouting and on-site suitability / acceptance testing and lock-off of all anchors;
  • Installation and load testing of five full-scale Proof Anchors;
  • Excavation for, and construction of substantial new reinforced concrete buttresses, wing wall extensions and ground beams;
  • Installation of rock bolts and rock-fall netting to steep slope above Eastern portal;
  • Concrete repairs to significant cracking within the existing walls, and painting;
  • Traffic Management (including tunnel closure, bus diversion, de-energising of O/H trolley wires), scaffolding, drilling, drainage works and other associated tasks.

The project specification required a high level of technical capability and quality control to undertake the full scope of works.  This included water-testing of drilled anchor boreholes, preliminary grouting and re-drilling, post-grouting of all ground anchors over repeated cycles, full-scale pull-out tests on Trial Anchorages, load testing and lock-off of DCP production anchors.

Poor ground conditions at some locations were encountered and this lead to additional testing and site survey’s which lead to revised construction details as developed in association with the Engineer.

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