O'Sullivan Dam



O'Sullivan Dam (National ID # WA00268), one of the largest earthfill dams in the United States (200 ft/61 m high; 19,000 ft/5,791 m long; completed 1949), is on Crab Creek in the U.S. state of Washington, about 45 km south of Ephrata and 25 km south of Moses Lake.

The 27800 acre Potholes Reservoir formed by this dam collects return flows from all irrigation in the upper portion of the project for reuse in the southern portion. A system of wasteways has been built on both the West and East Low Canals to provide operational safety for the canals and a means of delivering water into Potholes Reservoir to supplement the natural and return flows.

The dam was built as part of the Columbia Basin Project.

Statistics

 * Active storage capacity: 332,200 acre.ft
 * Structural height of dam: 200.0 ft (60 m)
 * Construction date: 1947-1949
 * Normal water surface elevation: 1052.0 ft (320.6 m)
 * Drainage area: 3,920.0 sq mi (10,153 km²)
 * Storm duration: 72 hr