Client
Hydro Tasmania
Location
Tasmania
Key Services
Technical Design Support, Upstream Geomembrane Design and Concept Evaluation
Outcome
Scotts Peak Dam, on the Huon River in Tasmania, impounds Lake Pedder. It is one of a series of lakes and dams supporting the Gordon Power Station owned and operated by Hydro Tasmania. The main section of this large dam is 43 metres high and was completed in 1973 as an asphalt-concrete-faced rockfill dam with a downstream slope that is reinforced near the toe. Together with two adjoining saddle dams, the dam has a crest length of just over 1,000 metres.
The owner engaged Geosyntec to evaluate concepts and implement a preferred alternative to improve the reliability of the dam under potential seismic loading. One of these alternatives consisted of lining the upstream dam face with an impervious geomembrane system and sealing the geomembrane to the plinth and parapet wall. The entire geomembrane system was installed underwater, keeping the reservoir at normal levels. We designed this project to minimise leakage during construction, support leakage monitoring after construction, and withstand future seismic deformations.
Geosyntec provided technical design support and review of the upstream geomembrane alternative for seismic upgrading of the dam to Damwatch Engineering, the owner’s design engineer. We evaluated the upstream geomembrane design concept and developed protocols and recommendations for testing and validation of the geomembrane system.
Notable elements of our scope included the following:
- Conducting a study to assess the seismic performance of the proposed geomembrane alternative
- Participating in design, construction, and associated risk assessment with the project team
- Reviewing and synthesising anticipated dam performance during the design earthquake to evaluate the design requirements for the geomembrane anchoring system
- Reviewing the geomembrane design details and materials to evaluate design requirements for the anchoring system based on known field conditions and anticipated seismic deformations
- Developing laboratory geomembrane testing and validation requirements for the geomembrane system
- Providing peer review and consultation on the numerical 2-dimensional dynamic response and deformation analyses performed with FLAC as part of the seismic deformation assessment
Geosyntec used our expertise in the engineering of geosynthetics and dams both in support of the project and as a liaison between the client and the geosynthetics manufacturer and designer to validate the geomembrane system design for possible future implementation and upgrade of the dam.
