Project Summary:
TransGrid required urgent remediation of aging transmission tower foundations before installing a new optical ground wire (OPGW) cable. PCA was contracted to provide a full design and construct solution for towers T125 and T126, which were suffering from severe anchor corrosion and posed a risk to safety and asset longevity.
Challenges
- Remote mountainous terrain with limited access
- No original design records or reliable geotechnical data
- Corroded rock anchors requiring complete replacement
- Concrete use infeasible due to transport restrictions
- Fixed 7-week delivery window based on planned line outage
- Unprecedented 10mm installation tolerance for micropiles (vs. 70mm industry standard)
Innovative Solution
PCA designed and installed a bespoke micropile system, each leg precisely connected with custom-fabricated steel brackets using finite element modelling (FEM). Key innovations included:
- Custom steel templates to control micropile alignment
- Helicopter-lifted equipment for Tower 125 access
- Winch-slide access system for Tower 126
- Modular lightweight machinery for remote transport
- Prototype testing and FEM validation
- World-first connection system, now patented globally
Outcome
- Tower foundation life extended without environmental disruption
- Precision alignment achieved with less than 10mm deviation
- Delivered on time within a tight 7-week construction window
- Eliminated the need for concrete batching in remote terrain
- Set a new industry benchmark in transmission tower remediation
