St Clair Lagoon radial gates replacement

Client: Hydro Tasmania
Location: Tasmania
Dates: 2024–26

Contributing spatial and mechanical expertise to replace heritage hydropower infrastructure

Background

At the southern end of Lake St Clair, within Tasmania’s Wilderness World Heritage Area, 8 radial gates have regulated water flows through the Derwent catchment since the early 1930s. The gates form part of Hydro Tasmania’s Tarraleah hydropower scheme and play an important role in managing lake levels and downstream water releases. Despite operating only occasionally, their reliability is critical.

After more than 90 years of service in one of Tasmania’s most challenging environments, the gates required replacement to ensure their ongoing performance and safety. The project presented several complexities: maintaining the heritage character of the original infrastructure, improving structural performance, and delivering construction works in a remote, environmentally sensitive location within the Cradle Mountain – Lake St Clair National Park.

Hydro Tasmania engaged Entura to provide specialist surveying and mechanical engineering expertise to support the renewal of this significant piece of hydropower infrastructure.

Solution

Entura combined advanced surveying technology with specialist mechanical engineering analysis to inform a replacement solution that would preserve the character of the gates while enhancing their long-term performance.

Using state-of-the-art equipment, Entura carried out precision surveys of the existing gates and associated structures. The resulting high-accuracy spatial data provided the foundation for detailed engineering assessment and informed the design of the replacement gates.

Entura’s mechanical engineers undertook detailed computer modelling and structural analysis of the original gate design. This work identified opportunities to strengthen critical components and improve performance while retaining the gates’ original appearance, dimensions and method of operation.

The engineering assessment led to a range of design enhancements, including increased structural strength in areas subject to higher stresses and improved side-seal arrangements. Modern fabrication techniques enabled stronger, single-section components to be manufactured offsite, delivering greater durability than was possible when the original gates were built in the 1930s.

Outcome

The project successfully delivered 8 new radial gates, each weighing almost 3.5 tonnes and measuring approximately 5 m by 3 m, providing a modern, resilient asset while preserving an important piece of Tasmania’s hydropower heritage.

Installed in challenging conditions and within a highly sensitive World Heritage environment, the new gates maintain the look and operation of the originals while incorporating significant engineering improvements. The project also included refurbishment of the gate hoist mechanisms and installation of a lubrication system to support ongoing reliability and maintainability.

By combining precise surveying, detailed engineering analysis and practical mechanical design expertise, Entura helped Hydro Tasmania deliver an infrastructure upgrade that balances heritage preservation with modern performance requirements.

The renewed gates will ensure that this historic structure remains a reliable part of Tasmania’s renewable energy system long into the future.

Services

• Precision surveying of 8 heritage radial gates and associated structures
• Detailed mechanical assessment, modelling and structural analysis
• Mechanical design advice to improve strength, durability and sealing performance