AHSAHKA, Idaho – The Walla Walla District of the Corps of Engineers placed Dworshak Dam’s hydroelectric generator Unit 3 back in service yesterday after completing repairs of damage due to a short circuit in the stator winding on Aug. 15. The unit faulted to ground and had to be taken out of service on Aug. 15 for replacement of a damaged electric coil deep inside the generator.
Repairs required partial disassembly and lifting of Unit 3’s large 400-ton rotor assembly, replacement and repair of several components, and reinstallation of the rotor assembly in the generator housing. The unit provides 55 percent of Dworshak’s powerhouse flow discharge and is the largest single hydroelectric power generator in the Corps of Engineers. Difficult repairs to the massive unit required significant effort, and were accomplished as planned in minimal time considering the generator’s size and complexity.
Dworshak’s reservoir water is normally used to cool the lower Snake River basin during the summer to support juvenile salmon as they migrate downstream,, plus adults migrating upstream. When the generator went offline on Aug. 15, the Corps reduced water flows through the powerhouse and increased spill through dam regulating outlets outside of the powerhouse. Though more water was spilled outside the powerhouse when Unit 3 went offline, overall discharge flows had to be reduced to manage total dissolved gas levels in the river, which can be harmful to fish.
Dworshak Dam total discharge flows will continue at 2,400 cubic feet per second. Dworshak Reservoir is expected to reach its normal fall elevation of 1520 feet on or about Sept. 25.
For more information about Walla Walla District operations, see the District website at www.nww.usace.army.mil.
Release no. 14-075