Cethana Dam cavern – extensometer monitoring

Client: Hydro Tasmania
Location: Tasmania, Australia
Date: Sep 2014 – Ongoing

Developing monitoring and data solutions to inform safe upgrades to an underground power station.


Cethana Dam is located in North West Tasmania. Housing the underground power station and located within the dam foundations, the Cethana Dam cavern was commissioned in 1971 and was excavated in conglomerate strata, which proved to be more blocky and variable during construction than anticipated.

Recent engineering activities by Hydro Tasmania, including desktop studies, site inspections, NDT testing and rock bolts over-coring, have demonstrated the necessity of additional tendon supports within the cavern and power station structure. This was to ensure a safe working environment for the upcoming machine modernisation outage for the power station.

To complete these activities, stresses within the cavern and power station structures at defined locations had to be actively monitored. Extensometers were used to complete this task.


After the installation of the first eight extensometers at the site, Entura identified challenges with the data retrieval solution in place. To overcome these challenges, we installed data logging and telemetry systems to automate the collection and archiving of data from existing and future instruments into the Ajenti™ Data Management System (ADMS). Data can be managed and dynamically displayed in the ADMS, including potential fault diagnosis operations.

These systems also had to have the ability to be operated dynamically and to trigger alarms both onsite and to relevant staff beyond defined monitoring limits.

Data display dashboards and data alarms were setup onsite through the monitoring control device and within ADMS to assist our client with viewing the required data in near real time.


Throughout the project, Entura worked closely with the instrument installation contractor and Hydro Tasmania to develop, design and install a cost-effective system that would meet all requirements.