A Collaborative Approach
The project began with early collaboration (ECI) to define the scope, identify risks, and agree on the best way to approach the work. CB Civil combined civil construction know-how with Northpower’s electrical expertise to fine-tune the programme and methodology.
This project integrated multiple engineering disciplines across the civil and electrical sectors. As a team of specialists, we coordinated with our partners to focus on a common goal - delivering the project to a high standard of quality, safety, and timeliness. Our ability to do this successfully was recognised by Transpower at the STAR awards in 2025.
Stages of Delivery
Establishment: Installation of traffic management controls and site facilities for the expected duration of works (up to 6 months) per joint bay.
Temporary Work & Excavation: Installation of pile and plate temporary work solutions to accommodate the required excavations up to 4m in depth to expose the existing joint bays and cables for the required extension footprint.
Flowable Thermal Backfill (FTB) Demolition: Establishing and implementing a tried and tested methodology to safely demolish the FTB concrete (up to 25 MPa in strength) which surrounded the highly sensitive 220 kV cables that had to be reused.
Joint Bay Extension: Structural extension of the existing joint bays to accommodate the installation of new joints, involving in-situ and pre-cast concrete elements.
Backfill & Removal of Temporary Works: After the jointing work had been completed, selective thermal resistant material was carefully placed and backfilled around the newly installed joints and cables with progressive removal of temporary works as backfil
Reinstatement: The works areas were reinstated to conditions equal or better than what they were before (and in most cases, better).
repaired
transmission line
of concrete broken out by hand
with no major incidents
Selected Methodology
The underground cables were encased within flowable thermal backfill (FTB) concrete. To prevent any damage to the cables, over 750+ tonnes of concrete had to be carefully broken out by hand, following a distinctively refined method to safely remove the concrete. This gave the specialist joining team the access they needed to complete repairs before our crews reinstated each bay.
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