Commissioning of spillway in early October was preceded by pre-operational tests of the facility, which took place from 28 September to 1 October. The tests included step-by-step opening of segmental gates at the inlet crown until they were fully opened (9.5m), enabling water to pass through the structural elements ready for operation: two tunnels, five-spot drop and tail race. At that maximum water flow passage over the spillway amounted to 3000m3/ses. Tests have shown that the hydraulic engineering structures are in satisfactory operational condition and the spillway is ready for commissioning and constant operation.

Construction of the onshore spillway for Sayano-Shushenskaya plant in addition to the existing dam spillway was initiated in 2005 to considerably increase the reliability and safety of hydraulic engineering structures of the power plant. The spillway is intended primarily for passage of extreme floods and may also be in occasionally used for passage of common floods. The Sayano-Shushenskaya onshore spillway will allow additional water flow passage of up to 4000m3/sec.

Reconstruction work is also currently being carried out at the project following on 17 August 2009, when water flooded the machinery hall, damaging the project’s power and auxiliary equipment and collapsing the frameworks of the machinery hall building. Seventy-five people were killed in the accident.