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22ndnd IMPACT WORKSHOP, Mo i Rana, Sept. 2002 IMPACT WORKSHOP, Mo i Rana, Sept. 2002

Risk analysisRisk analysis

Norwegian practice - new researchNorwegian practice - new researchby Grethe Holm Midttømmeby Grethe Holm Midttømme

The Norwegian Water Resources and Energy Directorate (NVE)The Norwegian Water Resources and Energy Directorate (NVE)

Photo: NVEPhoto: NVE

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The Norwegian Water Resources and Energy Directorate (NVE)

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Norwegian practiceNorwegian practice

Development of RA for dams in Norway - brief Development of RA for dams in Norway - brief overviewoverview

•1987: First project initiated by NVE and EBL (RA for 2 dams)1987: First project initiated by NVE and EBL (RA for 2 dams)

•1987-1995: A few projects on RA for dams, spillway gates and 1987-1995: A few projects on RA for dams, spillway gates and penstocks, among others a project on estimation and comparison of penstocks, among others a project on estimation and comparison of the probability of failure in large rockfill dams using event trees the probability of failure in large rockfill dams using event trees (Johansen et al. 1997, Hydropower’97)(Johansen et al. 1997, Hydropower’97)

•1995 - 2002: Several risk analyses performed, mostly probabilistic 1995 - 2002: Several risk analyses performed, mostly probabilistic event tree analyses, e.g. RA of the rockfill dam Valldalen (Funnemark event tree analyses, e.g. RA of the rockfill dam Valldalen (Funnemark et al. 2000, Q.76, ICOLD congress Beijing) et al. 2000, Q.76, ICOLD congress Beijing)

•Very few analyses include consequence analyses, i.e. assessment of Very few analyses include consequence analyses, i.e. assessment of probabilityprobability of failure is emphasized of failure is emphasized

G.H.Midttømme - 2G.H.Midttømme - 2ndnd IMPACT WORKSHOP, Mo i Rana, Sept. 2002 IMPACT WORKSHOP, Mo i Rana, Sept. 2002

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Norwegian practiceNorwegian practice

Development of RA for dams in Norway - brief Development of RA for dams in Norway - brief overview overview (continued)(continued)

In general: In general:

•Dam owners seem to use PRA’s mainly as a systematic way of Dam owners seem to use PRA’s mainly as a systematic way of identifying deficiencies and ranking safety improvements, e.g. as part identifying deficiencies and ranking safety improvements, e.g. as part of a dam safety reassessmentof a dam safety reassessment

•PRA methodology usually include: site inspections, hazard PRA methodology usually include: site inspections, hazard identification, construction of event trees, probability assessment identification, construction of event trees, probability assessment (statistics and engineering judgment) and evaluation of results(statistics and engineering judgment) and evaluation of results

• A method for consequence analysis adapted to Norwegian A method for consequence analysis adapted to Norwegian conditions has been developed (Funnemark et al. 1998, ICOLD conditions has been developed (Funnemark et al. 1998, ICOLD European Symposium on Dam Safety in Barcelona 1998)European Symposium on Dam Safety in Barcelona 1998)

G.H.Midttømme - 2G.H.Midttømme - 2ndnd IMPACT WORKSHOP, Mo i Rana, Sept. 2002 IMPACT WORKSHOP, Mo i Rana, Sept. 2002

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Norwegian practiceNorwegian practice

Regulations and guidelinesRegulations and guidelines

Revision of the first dam safety guidelines (1981) included a working Revision of the first dam safety guidelines (1981) included a working group on risk analysis and emergency action planninggroup on risk analysis and emergency action planning

• 1997: Guidelines on application of RA for dams (NVE)1997: Guidelines on application of RA for dams (NVE)

• 1999: Guidelines on the use of PHA for emergency planning (EBL)1999: Guidelines on the use of PHA for emergency planning (EBL)

• 2001: New regulations on dam safety 2001: New regulations on dam safety (§2.8 - NVE may demand risk (§2.8 - NVE may demand risk analyses conducted by the responsible dam owner)analyses conducted by the responsible dam owner)

• 2001: Practical guidelines describing how to perform event tree and 2001: Practical guidelines describing how to perform event tree and fault tree analyses (EBL)fault tree analyses (EBL)

G.H.Midttømme - 2G.H.Midttømme - 2ndnd IMPACT WORKSHOP, Mo i Rana, Sept. 2002 IMPACT WORKSHOP, Mo i Rana, Sept. 2002

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Norwegian practiceNorwegian practice

Regulations and guidelinesRegulations and guidelines (continued) (continued)

There are plans for developing new guidelines on application of RA There are plans for developing new guidelines on application of RA (NVE) ->(NVE) ->

focus will probably be on qualitative methods and analyses for EAPfocus will probably be on qualitative methods and analyses for EAP

Planned ICOLD-bulletin on Risk Assessment in Dam Safety Planned ICOLD-bulletin on Risk Assessment in Dam Safety Management andManagement and

ongoing projects related to risk analysis will be looked at ongoing projects related to risk analysis will be looked at

G.H.Midttømme - 2G.H.Midttømme - 2ndnd IMPACT WORKSHOP, Mo i Rana, Sept. 2002 IMPACT WORKSHOP, Mo i Rana, Sept. 2002

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New researchNew research

Recent dr.ing. studies at the Norwegian Recent dr.ing. studies at the Norwegian University of Science and Technology University of Science and Technology (NTNU), Trondheim(NTNU), Trondheim

Hilde Marie Kjellesvig: Dam Safety - The Passage of Floods that Hilde Marie Kjellesvig: Dam Safety - The Passage of Floods that Exceed the Design Flood, Thesis published July 2002 Exceed the Design Flood, Thesis published July 2002

Parts of the research work has been done in close cooperation with Parts of the research work has been done in close cooperation with the project ”Stability and Breaching of Embankment Dams”the project ”Stability and Breaching of Embankment Dams”

Grethe Holm Midttømme: Flood Handling and Emergency Action Grethe Holm Midttømme: Flood Handling and Emergency Action Planning for Dams, June 2002Planning for Dams, June 2002

G.H.Midttømme - 2G.H.Midttømme - 2ndnd IMPACT WORKSHOP, Mo i Rana, Sept. 2002 IMPACT WORKSHOP, Mo i Rana, Sept. 2002