Case study: Sayano Shushenskaya hydroelectric power plantIntroduction: Located on the Yenisei River, closest to Sayanogorsk in Khakassia, Russia, the Sayano-Shushenskaya hydroelectric power plant opened in Soviet era in 1978. In 2009, the plant ranked sixth in the world and first in Russia in gross hydroelectric power generation. A total of ten turbines were used to supply 6,400 MW of electricity to Russian infrastructure.1 When workers arrived at the plant around 08:00 on August 17, 2009, there was no cause for immediate alarm. Of the ten turbines, nine were working and a tenth was down for routine maintenance. Turbine two, however, caused significant vibrations as its load varied with electricity demand. At 08:13 the turbine bearing vibration reached its maximum and caused a catastrophic failure. The turbine cover lifted as the 1,000 t rotor broke away from its seat. The newly created hole in the structure allowed water to flow at a rate of 67,600 gal s-1 into the engine room and flood the levels below.2 The massive jet of water tore through the metal beams supporting the roof above that of the turbines, two and three. As the roof collapsed, water continued to flood the plant. Long after the automatic safety system should have activated, turbines seven and nine were still running at full speed, causing what were seen as large explosions in their vicinity as the flood reached their control panels. Fortunately, at 09.20 the 170 t of steel water inlet gates of each turbine were closed manually using safety valves on the hydraulic support jack of each gate. At 11.32am a diesel generator was brought in to restore electricity to the area. Later, at 11:50 a.m., 11 spillway gates were opened to dump the excess…half of the paper…this is also taught here, as workers at the plant had never completed any emergency drills and a backup generator has not been installed to provide energy to the plant itself in case of emergency. Much of the reason for Turbine Two's failure, however, lies in human hands. Maintenance and inspection personnel clearly knew that intense vibrations were not normal, but the turbine was still being used. This could also have fallen on management, as they would have to ensure that maintenance directives were followed. In this regard, it should be noted that immediately after the explosions, as many people fled, several supervisors in charge of security and emergencies also fled. Ultimately, this was an entirely avoidable disaster, caused by human negligence, exacerbated by mechanical fatigue, and ended with lessons learned at great cost..