Fort Peck Dam
The Fort Peck Dam is one of the more interesting if lesser known dams in the United States. It is the largest dam on the Missouri river but what makes it so interesting is actually the way that it was built. While not an uncommon means of construction you don't usually see hydraulically filled dams that are as big as the Fort Peck Dam.
The Fort Peck Dam is located on the Missouri River in Montana and it is one of the biggest dams in the United States. With a length that is nearly four miles long it is much larger than most other dams. It is also one of the largest hydraulically filled dams in the world. The dam was originally constructed in large part as a make work project during the depression. There were two goals for the dam, it was supposed to provide both electricity and water for irrigation. It is one of six dams that have been built along the Missouri River and the largest by quite a margin.
The construction of the Fort Peck Dam is rather interesting because of the choice to go with a hydraulically filled dam. That meant that they literally dumped dirt and rock into the river and allowed to flow downstream forming the dam. The actual construction process is somewhat more complicated than that because of the need to accurately control where the construction material ends up and how fast it gets there. One of the advantages of building in this way is that it is probably the least expensive way to build a dam.
One of the oddities of building the Fort Peck Dam was the need to build a shipyard in Montana. Construction required several dredges to clean up river bottom and collect the material that would be used to build the dam. With Montana being so far from the coast and there being no practical way to get dredges to the area they decided to build them right on site.
Unfortunately the construction of the Fort Peck Dam did not go well. As the dam neared completion it failed. An investigation into the cause of the failure revealed that some of the material that had been used in the construction was too porous and had allowed water to pass through it.
The Reservoir behind the dam is known as Fort Peck Lake and it is the fifth largest man made lake in the United States. The water from the lake provides power to five generating units at the power station. Compared to other dams the amount of electricity that is produced is fairly small but it is important to the area. Equally important is the use of the water from the lake for irrigation as well as the ability to control the levels of the Missouri River.