McNary Dam II

McNary Dam is a 1.4 mile (2.2 km) long hydroelectric dam which spans the Columbia River. The Dam is 292 miles (470 km) upriver from the mouth of the Columbia at Astoria, Oregon. The dam provides for slackwater navigation, hydroelectric power generation, recreation, wildlife habitat, and incidental irrigation.

This dam has a unique feature: two additional turbines whose purpose is to power the dam itself. That is, this dam is entirely self-sustaining; and if some large event caused the entire grid to go down, McNary would be key in getting it back on. These two "station service" turbines are only capable of providing about three MW, compared to the 70 MW of the other 14 turbines. These two turbines operate alternatingly to provide the dam with its energy requirements.

McNary Dam is part of the Columbia River Basin system of dams.

-Taken from Wikipedia