Hydro’s internal investigation of the accident on May 9 at the Svandalsflona power station in western Norway has concluded that the most likely reason for the accident was that water that had built up behind a mass of rock in a shaft inside the facility gave way, flooding the power station and causing two deaths.
The results of the investigation will be given to the police, which are investigating the accident.
A final verification of the reasons behind the accident must wait until the shaft can be inspected after the snow melts. The two men who died were employed by Veidekke Entreprenør AS and a subcontractor.
The investigation found that the pressure from the water that had gathered behind the rock mass that was being removed from the shaft gave way, which resulted in rock mass and water quickly flooding into the tunnel where the men were working.
In June 2008, it was concluded that a rock slide had occurred from the top of the shaft near a water intake for the Svandalsflona power station. About 900 cubic meters of rock mass had collected in the lower part of the 180-meter-long shaft, which leads water into the main tunnel about 1,000 meters from the power station.
The accident occurred during work to remove the mass from the rock slide. At the time of the accident, about 600 of the 900 cubic meters of rock mass had been removed. According to the investigation, 600 to 1,000 cubic meters of water may have been trapped behind the rock mass.
Both external expertise as well as Hydro own competence were being used in connection with the planning and execution of the work for removing the rock mass. Several geological studies and inspections were carried out in cooperation with external experts.
Risk analyses were done in the planning stage and execution phase for the various tasks that were being carried out. Afterwards, it has been found that the full risk connected to a possible gathering of water behind the rock mass was not identified.
The investigative committee included representatives from Hydro, Veidekke, Statkraft and external consultants.
Independently of what the police conclude about the accident, Hydro will conduct a review of the relevant procedures for this type of project.
- Press contact
Halvor Molland, vice president, Media Relations, Hydro