Nathaniel "Nat" Washington Power Plant Overhaul Project — Project Summary
This project will involve overhauling and modernizing units G19 through G24 in the Nathaniel “Nat” Washington Power Plant. The units have been in service since the mid-1970s and have been heavily used over the years. Their condition has deteriorated, and a complete overhaul is necessary to ensure these machines will continue to operate reliably. Work will be performed on generators, turbines, shafts, and auxiliary equipment to ensure another 40 years of dependable service.
Units G19–G21 are equipped with 820,000-horsepower Francis turbines, designed by Dominion Engineering Works, Ltd., and manufactured by Willamette Iron and Steel Company with a runner throat diameter of 34 feet. Units G22–G24 are equipped with 960,000-HP Francis turbines, designed and manufactured by Allis-Chalmers with a runner throat diameter of 32 feet.
Generators G22–24 were overhauled between 2012–2021. They are rated to produce a total of 2,415 mega-volt-amps with an annual power production value of over $100 million. The overhaul work included inspecting, refurbishing, or replacing worn mechanical and electrical components, including bushings, seals, controls, and deteriorated wiring. Rotors were inspected and repaired as needed.
Units G19–21 is projected to be overhauled and modernized beginning in 2026; this includes a possible uprate. Collectively, these three smaller units currently provide 1,845 MVA—615 MVA each. Recent studies have shown that the Nathaniel “Nat” Washington Power Plant G19–G21 generator windings and shaft, and turbine runners, need replacement to achieve uprate up to 790 MVA each. Power system officials are looking at cost-benefits that consider uprate value and reduction of triennial cavitation repair to determine if this investment is economically justifiable.
A considerable amount of the planning and design work was involved to accomplish the overhaul of units G22–G24. Reclamation is working with the Bonneville Power Administration and U.S. Army Corps of Engineers determine the G19–G21 contract scope and get the modernization project underway. These efforts will collectively result in improved reliability of six of the largest hydroelectric units in North America for several more decades.
Contact
Brian Clark
Project Manager
bdclark@usbr.gov
(509) 633-9693
