Grand Coulee Dam, on the Columbia River, is the largest concrete structure ever built. It raises the water surface 350 feet above the old riverbed.
     The dam is 5,233 feet long, 550 feet high and contains 11,975,500 cubic yards of concrete.
     Construction began in 1933 and was completed in 1942. The first power was generated in 1941 and the last of the original 18 units began production in 1950.
     Pumping for irrigation began in 1952. Construction of the Third Powerplant and Forebay Dam began in 1967; the last unit went on line in 1980.
     The Columbia Basin Project, of which Grand Coulee Dam is a part, is a multi-purpose development and includes an extensive irrigation works extending 125 miles southward on the Columbia Plateau.
     Power production facilities at Grand Coulee Dam are the largest in North America.
     The original dam was modified for the Third Powerplant by addition of the 1,170-foot-long, 201-foot-high Forebay Dam along the right abutment roughly parallel to the river.
     Power facilities consist of power plants on the left and right sides of the spillway, plus the Third Powerplant, the pumping generation plant on the left abutment of the dam and accompanying switchyards.
     Average water released from Grand Coulee Dam is 110,000 cubic feet per second. The average power generation is 21 billion kilowatt-hours per year.
     Grand Coulee Dam provides flood control, irrigation, hydropower production, recreation, stream flows, and fish and wildlife benefits, according to the U.S. Bureau of Reclamation, which operates the dam.
     Franklin D. Roosevelt Lake, behind the dam, is 151 miles long with more than five million acre-feet of active storage.
     Water releases from Grand Coulee play a significant role in providing water for fish listed under the Endangered Species Act, according to the bureau.
     No bags or purses are allowed on the tour or in the Visitor Arrival Center for security purposes.
     The Visitor Arrival Center has been revamped. It includes new displays and more information on the dam's history.
     The summer Laser Light Show at Grand Coulee begins May 27 and continues nightly through Sept. 30.
     Times for the show are 10 p.m. May through June 30, 9:30 p.m. in July, and 8:30 p.m. in August and September.
     
More information:
     U.S. Bureau of Reclamation: http://www.usbr.gov/pn/grandcoulee/
     Grand Coulee Dam digital photo collection, University of Washington: http://content.lib.washington.edu/grandcouleeweb/index.html
     Grand Coulee Dam Area Chamber of Commerce: (509) 633-3074 or www.grandcouleedam.org
     Information on visiting the dam: (509) 633-9265
     Lake Roosevelt National Recreation Area water levels: U.S. Bureau of Reclamation, 1 (800) 824-4916.
     Recreation area: (509) 633-9441 or www.nps.gov/laro/index.htm; (509) 738-6266 or (509) 725-2715