At 2030 MT, the penstock separated, tripping the units at the powerhouse. The headgate closed successfully, and it was reported that the spillway could pass the expected flow rates. Two sections of pipe completely separated, including three dresser couplings. Only minor erosion occurred. Three penstock saddles moved significantly out of position and three others settled and will require leveling. Due to a blocked drainage culvert some water got into the generator sumps in the powerhouse. The automatic bilge pump pumped the water out and prevented it from reaching the generators. The East Diversion Dam (�low� downstream hazard potential rating) and powerhouse are undamaged. The EAP was not activated. The area has seen record rain and snow fall this winter, as well as additional rain and snow this spring. The ground around the penstock is extremely wet and saturated with moisture. Diameters of the steel penstock range from 31.5 to 34 inches over a length of 4.2 miles.
Failure Mode
Sections of the penstock separated.
Effect
Minor erosion occurred and the penstock saddles moved significantly.
