Lower Granite Dam

Lower Granite Lock and Dam was the fourth of four dams in the Lower Snake River Project, authorized in the Rivers and Harbors Act of 1945. Construction began in 1965. Three turbine units were operating in 1975. Three more came online in 1979.

The dam stands at Snake River mile 107.5 near Pomeroy, Washington, at the upstream end of Lake Bryan. The Corps lists it as about 3,200 feet long with an effective height of 100 feet. It is a concrete gravity dam with an earthfill right-abutment embankment, a navigation lock, powerhouse, and fish ladder.

Lake Lower Granite extends 40 miles upstream to Lewiston, Idaho. The Corps built roughly eight miles of levees around Lewiston. The project provides hydropower, navigation, flood risk management, fish and wildlife habitat, recreation, and incidental irrigation. The sources below are U.S. Army Corps of Engineers fact sheets.