Blackman River dam safety reviews
Client: TasWater
Location: Tasmania / Australia
Date: January 2020 - June 2023
Conducting dam safety reviews to identify and analyse risks in alignment with ANCOLD guidelines
Background
Blackman River is located in Tasmania and is home to 2 dams (Blackman River No. 1 dam and Blackman River No. 2 dam). One is a 9 m high concrete slab and buttress dam, which was constructed in 1939. The other is a 7 m high homogenous earthfill embankment dam, built in 1968.
For both dams, TasWater required a comprehensive dam safety review to identify risk mitigation options that would comply with the Australian National Committee on Large Dams (ANCOLD) ‘As Low As Reasonably Practicable’ (ALARP) requirements. Given the age and structural types of the dams, a detailed assessment was essential to ensure safety and compliance.
Solution
Entura was engaged by TasWater to systematically assess available data, identify gaps, and quantify risks associated with both dams. Entura’s method involved continuous engagement with the client and establishing key checkpoints to ensure alignment with TasWater’s expectations, including conducting a thorough review of existing information and identifying the potential risks and gaps through a collaborative workshop.
Entura also scoped, managed and reported on site investigations, including test pits and drilling at remote sites, to assess geological conditions and potential failure modes. We installed telemetered piezometers and conducted underwater inspections of mechanical assets to gather critical data, as well as developing hydrological models and performing dam break assessments along with consequence category evaluations.
In conducting engineering analyses, we completed structural assessments, piping risk evaluations, spillway capacity studies, erodibility assessments and dewatering assessments, and created F-N plots to visualise risk levels and ensure compliance with ANCOLD guidelines.
Following this, Entura led a collaborative workshop with our client and an independent reviewer to assess risk and explore upgrade options. A prioritised action plan was then produced, which included upgrade options and detailed cost estimates.
Services provided
- Data analysis and workshop facilitation
- Site investigations
- Instrumentation installation
- Hydrological modelling
- Engineering analyses
- Risk visualisation
- Options analysis workshop
- Action plan development
Outcome
Entura delivered a comprehensive risk assessment for our client, providing TasWater with a clear understanding of the dam safety risks associated with both structures. We also provided a quantification of failure modes with detailed metrics, including the Cost to Save a Statistical Life, F-N plots, and ALARP assessments, to support informed capital works planning. We also conducted an options analysis and provided regulatory compliance reporting.
Through our thorough comprehensive dam safety review, TasWater gained valuable insights into the safety risks at the Blackman River dams and the necessary information and cost estimates to pursue targeted dam safety upgrades.
This project is another example of TasWater and Entura working together to safeguard vital infrastructure to serve the Tasmanian community long into the future.
