CLOSED - River cut off June 24, 1937
June 24, 1937-a day of reflecting and putting the preceding 1,340 days before it into perspective. The Missouri River had been cut off. As the most meaningful carload of gravel fell from the Missouri River Bridge overhead (upper right), it was assured that history's pages would indeed pay tribute to thousands of people who invested millions of hours in a godsend project blessed by a savior known as FDR. One week after closure, the downstream gravel toe (lower right) was gaining height as bulldozers and draglines spread gravel dumped from railcars. This downstream section of the dam now serves as a burial ground for the Missouri River Bridge. Although closure took place in mid-1937, the dam was not totally finished until 1940 and the final topping wasn't complete until June of 1947.
The four-mile long dam was considered the engineering feat of its time. The dam contains 125.6 million cubic yards of fill, 97 percent of which is hydraulic fill. The remainder consists of rolled earth sheared from the abutment, which makes up a 3,000-foot section on the west end. Glacial till from that same abutment formed the core of the final raise of the dam. The dam also contains nearly 4 million cubic yards of gravel, more than half a million cubic yards of quarry stone and a third of a million cubic yards of field stone. Underseepage control is provided by a sheet steel cutoff piling driven into the shale below. Relief wells and trench drains allow for possible through seepage, which is normal. Such through seepage reduces the pressure on the foundation materials. The width of the base is 4,900 feet and was widened considerably following the slide of 1938. The top of the dam is 50 feet wide and stands 250 feet above the base. Damming height is 220 feet. The reservoir contained by the dam runs 134 miles long with some 1,600 miles of shoreline. Total storage exceeds 19 million acre-feet of water. (An acre-foot is equal to an acre of water one foot deep.)