Fort Peck Dam is one of the huge earth-filled dams along the Missouri River. Built in the late 1930s and finished in 1940, the project required over 11,000 workers. Fort Peck Lake, which extends for 134 miles behind the dam, is the fifth largest man-made lake in the US. The lake has 1520 miles of shoreline, and is as deep as 220 feet.

Completion of the dam was delayed when a section of dam collapsed and failed in 1938. The accident lead to the loss of 8 lives. The dam features 2 power plants. Powerhouse #1 has 3 units. It first started generating power in 1943, but was not completed until 1951. A second powerhouse was completed in 1961, adding 2 more power generation units.

Like most modern dams, the Fort Peck Dam has an emergency spillway to keep flood waters from overtopping the main earth-fill structure. In the case of the Fort Peck Dam, the spillway is located 3 miles from the main dam structure. This is to avoid having flood waters flow over the main dam. Rather, a more suitable soil was located at the head of a natural valley near the dam site. The spillway is over 800 feet wide and has 16 enormous steel gates.

The dam was built using the hydraulic earth-fill method. Large dredge boats were brought in. These boats dredges material from downstream of the dam. The material was pumped in 28 inch diameter pipes to the dam. The pipe system would deposit the dredged material at the dam with larger rocks making up the core, and finer material filling in the gaps. A wall of steel sheet pile runs across the base of the dam to prevent water from leaking under the dam.

The photo above is taken from the east end observation area. It shows an overview of the dam, which extends for 3-1/2 miles in the distance. The lake is to the left, and the river flows to the right. The structures in the foreground (shown closer below) are the control stations for the powerplant intake tunnels.

This is the roadway where it crosses the spillway. The spillway control building is to the right. The photo below is the side of the bridge that crosses the spillway. The spillway is located 3 miles from the main dam.

These are two more photos of crossing the bridge that carries Montana State Route 24 across the spillway.

The photo above is the downstream side of the spillway taken from the spillway observation area. The spillway is over 800 feet wide. The photo below is looking west across the dam from road level. The dam is very wide at the base, so you do not get the feeling that you are 250 feet above the normal terrain.

The photo above shows the two powerplants. Powerplant #2 is on the left, while powerplant #1 is on the right. Powerplant #2 has 3 generators, while powerplant #1 has two generators. The #1 powerplant was rebuilt and upgraded once since it went into operation in 1943. The vertical structures are surge towers. They act as small reservoirs to smooth out the flow of water to keep sudden surges in flow from damaging the turbines.

The photo above is looking downstream from the top of the dam. The museum is on the left, while the powerplants are just off to the right. The water is part of the outflow channel of the Missouri River. The photo below is taken from the bottom of the dam looking back towards the top. The lower section of the dam is part of the cofferdam built during construction of the dam. It is left uncovered in order to spot water leaks. The area above is the hydraulic fill. It is covered in grass, but is mowed regularly.