The World Almanac lists Fort Peck Dam as the largest embankment dam in the United States with the fifth-largest man-made reservoir. It is also the second-largest volume embankment dam and the largest “hydraulic fill” dam in the world.
Hydraulic fill dams are comprised of sediment pumped from the river bottom. The slurry was pumped through miles of huge pipelines to the centerline of the dam. The “core pool,” as it was called, ran the length of the dam, with water slowly draining back to the river while impervious material settled and formed the center of the dam.
Railroad cars then hauled rock and fill material via bridges, dumping their cargo on top of the layered embankment of the dam.
The Fort Peck Dam served as a model of design for the vast majority of major earth-fill dams built after it.
The embankment stretches four miles across the Missouri River Valley and contains 126 million cubic yards of earth fill.
Fort Peck Lake is 134 miles long at a normal operating level, with 1,600 miles of shoreline. Ninety-nine percent of the water released from Fort Peck Dam - or about 6.5 billion gallons per day - passes through the power plant. That translates into 2.8 million kilowatt-hours of pollution-free energy produced each day, on average.
Reprinted from Corps of Engineers brochure.