Meadowbank Dam Safety Review – stages 1, 2 and 3

Client: Hydro Tasmania
Location: Tasmania, Australia
Date: 2021-25

Services: Dam safety assessment, hydrological and hydraulic studies, mechanical reliability engineering, engineering geology, dam risk assessment

Providing specialist, multidisciplinary expertise to achieve a deep understanding of a dam’s performance and risk

Background

About an hour’s drive north-west of Hobart is Meadowbank Dam, constructed in 1968 as part of the Lower Derwent hydropower scheme. Meadowbank Dam is a 43 m-high concrete buttress dam (with prestressed anchors) and a concrete-faced rockfill dam (CFRD) on the right abutment. The centrally located spillway is controlled by mechanical flap gates.

Hydro Tasmania engaged Entura to complete a 3-stage Dam Safety Review (DSR).

Solution

Stage 1 of the DSR began with a comprehensive inspection of the dam, review of all historical data, gap analysis, engineering assessments (hydrological, geological, hydraulic, structural), and preliminary risk assessment. Stage 2 involved undertaking additional work to fill in the identified gaps that were critical to the risks identified, including site investigations of both foundation and concrete and further detailed engineering analysis, including 3-dimensional stability analysis. Finally, Stage 3 involved a dam risk assessment in compliance with ANCOLD guidelines, including an ALARP assessment (‘as low as reasonably practical’) to guide risk mitigation measures and a review of surveillance monitoring.

Outcome

Entura’s depth of dam safety knowledge allowed us to logically and cost-effectively deliver this multi-year multidisciplinary project.

Our specialists in dam engineering, geotechnical, hydrology and hydraulics worked closely and collaboratively to conduct a diverse array of specialist studies to better understand the risks associated with this dam. The study also included climate change modelling, to fully understand the dam’s risk position and how this might change into the future.

Our DSR of Meadowbank Dam delivered several key findings, providing essential insights for Hydro Tasmania as it manages and prioritises works on its portfolio of 54 major dams, ensuring the dam safety monitoring program aligns.

With Entura having thoroughly investigated the dam’s structure and assessed its compliance with modern dam safety standards, Hydro Tasmania now has a clear picture of Meadowbank Dam’s current performance, credible failure modes and associated risk profile. Our detailed safety review will support Hydro Tasmania to make informed data-driven decisions and prioritise risk reduction works appropriately across its large portfolio of dams – supporting the long-term safety, sustainability and reliability of these crucial assets for generations of Tasmanians.

The final Stage 3 DSR also provided a clear understanding of the key aspects to focus on when exploring potential upgrade designs.