Commercial Bay is one of the largest mixed use developments in Auckland and one with the highest profile in the city's history.
The development of New Zealand’s tallest building will entail construction of a 39 floor graduated glass skyscraper that has a multi-level 18,000m2 retail precinct above ground, a three-level basement and incorporation of the new City Rail Link (CRL) tunnels.
Project challenges
There are complex technical and logistical challenges with the development of Commercial Bay because of its location in the heart of Auckland’s CBD.
The basement requires up to 12m deep excavations through historically reclaimed ground and bedrock below harbour level, while supporting and excavating beneath the foundations of adjacent high-rise buildings.
The CRL tunnel boxes within the site have been designed so that they are structurally independent of surrounding buildings and basements, to provide noise and vibration isolation as well as future-proofing for ongoing developments. The tunnel stubs will connect to the CRL extensions following completion of basement construction.
The new basement will be designed to integrate with the existing basements, and allow connection below the water table within the reclaimed ground.
These technical challenges are compounded by the congested buried services surrounding the site and the need to keep one of the busiest pedestrian and transportation areas in Auckland moving freely and safely.
Construction of Commercial Bay commenced in July 2016 and completion of ground works is programmed for late 2017.
Services provided
T+T provided a range of consulting services, the most notable being geotechnical and hydrogeological, infrastructure and contamination engineering design and flood mitigation expertise. T+T’s key contributions to the project include:
- Geotechnical design of all aspects of the project, including permanent and temporary retention, anchorages, underpinning works and design of foundations
- Detailed assessment of geotechnical and groundwater effects upon sensitive neighbouring structures, including the Category 1 listed heritage Customhouse and Endeans buildings
- Planning for construction monitoring of effects and contingency measures
- Civil design of all external services, including coordination of relocations, protection and connections to meet contractor, local authority and utilities providers approvals
- Erosion and sediment control planning
- Flood hazard assessment
- Environmental and contamination services throughout the design process, including management planning for soil and water treatment and disposal
Innovation and value engineering
T+T’s geotechnical design of the underpinning works for the basement and CRL tunnels will allow excavation directly adjacent to and beneath the foundations of the fully occupied 17 storey Zurich building. The design has simplified the works and will provide a more robust approach for this time-critical piece of the project.
In addition, the team has also worked closely with the contractor to refine the diaphragm and sheet pile wall and anchorage designs, to optimise the construction sequence and minimise capital costs.
T+T is proud to have played a key part in bringing this project from concept design in early 2014 to design completion in 2016 by helping to accelerate critical path activities.