Dinas Reservoir Dam Safety Risk Assessment Workshop
Project : Dam Safety Risk Assessment Workshop
Client : Statkraft
Date of Services : October to November 2023
Scope of work
- Participation by Stillwater Panel Engineers in 2-day workshop held at Rheidol Hydropower Plant.
- Identify potential trigger events and associated failure modes for Dinas Dam.
- Use event tree analyses to quantify the annual probability of failure of each credible failure mode identified.
- Comprehensive write-up of the workshop notes.
Project description
Dinas Reservoir is located on the Afon Rheidol approximately 1.3km north of Ponterwyd and 18km east of Aberystwyth, Ceredigion. The reservoir is retained by an approximately 26.5m high and 108m long concrete arch-gravity dam, built around 1957 to 1962. The reservoir is owned and operated by Statkraft Energy Ltd. for the purposes of electricity generation as part of the Rheidol Hydro-electric Scheme.
Dinas Dam is known to be suffering from Alkali-Aggregate Reaction (AAR) in the concrete, with the first symptoms noted around 1980 and various investigations and works completed at Dinas dam since then. As part of their ongoing reservoir safety management regime, Statkraft earmarked Dinas Reservoir for a dam safety risk assessment in 2023 to be undertaken in the form of a workshop attended by members of the Statkraft dam safety team and independent Reservoir Panel Engineers of Stillwater Associates. The main aim of the workshop was to identify potential failure modes for Dinas dam and what could trigger these failure modes. Event tree analyses were then used to quantify the annual probability of failure of the dam for each credible failure mode identified. Statkraft would ultimately use the results of the risk assessment to prioritise capital works to ensure the ongoing satisfactory operation of Dinas Dam.
The Stillwater team, comprising Tom Wanner, Peter Mason (both All Reservoirs Panel Engineers) and Hermann Stehle (Supervising Engineer), contributed significantly to the success of the workshop. In addition, the team produced a comprehensive, technical write-up of the workshop notes which formed the basis for the final internal Statkraft report.
