Project Overview:
Constructed in 1962, Transmission Lines 4 and 5 span 120 km between Yass and Marulan, NSW, comprising over 400 steel lattice towers across farmland and conservation zones. In 2016, field assessments revealed extensive corrosion in the original steel grillage foundations, prompting the need for foundation strengthening to extend the operational life of the lines by an additional 50 years.
PCA Ground Engineering was selected to deliver a low-impact, cost-effective foundation remediation solution under live line conditions—successfully replacing and reinforcing 37 tower foundations using their patented K-LOK™ system. This project marked the first implementation of the K-LOK™ system in the TransGrid network and laid the foundation for future upgrades across over 5,000 transmission towers.
Challenges
- Corroded steel grillage foundations at 37 tower sites
- Work required under live 330kV conditions with strict safety constraints
- Limited access and minimal design documentation for 59-year-old structures
- Need for non-invasive methods and minimal disruption to surrounding environments
- Complex structural design to transfer shear and axial loads without inducing bending
- Requirement for long-term durability and reduced cost versus traditional methods
Innovative Solution
PCA deployed its K-LOK™ micropile system, designed to transfer axial and shear loads directly into deep foundations without compromising existing tower structures. Key features included:
- Micropiles installed parallel to the tower legs and connected with a precision-engineered steel bracket
- Brackets designed using finite element analysis to act as robust steel pile caps
- No concrete required, significantly reducing environmental and access track impact
- Lightweight, compact equipment allowed installation on all four legs in a single visit
- Thermal spray galvanising used for enhanced durability during rough transport and long-term exposure
- Installation of a sacrificial micropile and on-site testing for each tower to verify load performance
- Micropiles installed with tolerances to meet live structure demands without inducing structural stress
The K-LOK™ Advantage
- Installed under live line conditions—no power outages required
- Delivered at ~10% of the cost of full tower replacement
- Minimized community and environmental impact
- Design life of 50 years backed by testing and advanced galvanising methods
- Now officially adopted in TransGrid’s technical specifications for future remediation
- Enabled scalable planning for future upgrades across TransGrid’s network of 5,000+ towers
Outcome
- Life extension of critical infrastructure at a fraction of the replacement cost
- Recognised by TransGrid for innovation, reliability, and safety
- System now considered industry-leading for foundation remediation in live high-voltage environments
- Set a new standard for structural foundation upgrades across the Australian transmission grid
