NWPPA Bulletin, Jan. 2017, by John Barksdale. -- scroll to page 12 of the .pdf.
https://www.nwppa.org/wp-content/uploads/Bulletin_Jan_2017_WEB.pdf

"Idaho Falls Power, a department of the City of Idaho Falls and one of the oldest public power utilities in the Northwest, is situated on the Snake River in Southeast Idaho....  Today, IFP now owns and operates five hydroelectric facilities generating 56 megawatts for its 27,000 customers. The oldest of its hydro projects, the Old Lower Plant, was built during the Roosevelt Administration in 1938 under the Works Progress Administration.... Given the age of the generators, turbines, and the plant in general, IFP evaluated rebuilding the units to determine if it was an economically viable option. The analysis demonstrated a return on investment over a 35-year period using several energy cost scenarios. With an estimated rehabilitation cost of $7.8 million, the feasibility was deemed viable in all scenarios."