Page - 1123 - in Book of Full Papers - Symposium Hydro Engineering

SUMMARY Among the 1200 dams classified in Switzerland, 167 are large dams according to ICOLD standards. The Swiss Federal Office of Energy (SFOE) is entrusted with the overall supervision of the enforcement of the legislation, which comprises the development of the safety concept and dam safety requirements published in form of Guidelines. The SFOE is also entrusted with the direct safety supervision of the 217 largest dams in view of their impounding head, storage capacity and hazard potential for the population in the area downstream of the dam. These are categorized into 124 concrete dams, 66 embankment dams and 27 run-of-river hydropower plants. The latter are deemed to be in the interest of public safety mainly for their relevant storage capacity. With the new Dam Safety Legislation in Switzerland (2012), large run-of-river hydropower plants along main rivers became subjected to in-depth safety assessments under the direct supervisory authority of the SFOE based on the specific Enforcement Guideline of the Dam Safety Legislation (2015). The Swiss dam safety concept, apart from continuous surveillance, maintenance and emergency planning also entails such periodic in-depth safety assessments. This consists in a review of hydraulic and structural actions (static, flood and seismic) for all water-retaining structures and safety-critical appurtenant components of such an installation, including lateral embankments or dams within the storage area. Present structural, hydraulic, hydrogeological, geological, steel-structural and process control technology state of all above components require an assessment, as well as implemented surveillance and maintenance practices. If necessary, based on actual scientific and technical state of knowledge, improvements are recommended and may be set into practice. Two case studies are presented in this paper. The two plants dispose of continuous surveillance (regular function tests of all safety-critical installations and equipment and yearly inspections by external experienced engineer), continuous update of an archive with relevant documents, continuous structural maintenance, adequate monitoring instrumentation and redundant control technology. Further, as all operational and hazardous load cases meet the requirements, it is allowed to conclude that safety of both plants is guaranteed in accordance to the Swiss Dam Legislation. A team of experts (civil, mechanical and electrical engineers and geologists) can perform straightforwardly a total in-depth safety review of such hydropower plants within a reasonable timeframe. KEYWORDS: Safety of Dams, Run-Of-River Hydropower Plants, Inspection and Assessment 1123