FERC issued guidance on Oct. 17 for developing closed-loop pumped-storage facilities at abandoned mine sites.

The guidance spotlights issues, including potential environmental impacts, for developers considering projects at abandoned surface pits or underground mines.

FERC also released a list of 230 nonpowered federal dams that have the "greatest potential for non-federal hydropower development," the commission said.

The Western dam on the list with the largest potential capacity, at 78.9 MW, is the U.S. Army Corps of Engineers' John Martin Dam in Colorado. The second-largest potential capacity in the West, at 26.3 MW, is the Corps' Howard Hanson Dam on Washington's Green River.