The Oahe Dam is the second largest dam on the Missouri River, and the 15th largest earth fill dam on the planet. In comparison, it contains more than twice the fill material as the Aswan High Dam on the Nile River. Lake Oahe extends for 231 miles up river towards Bismarck, North Dakota, and has 2,250 miles of shoreline.

Construction of the dam was authorized in 1944 by an act of Congress. The US Army Corps of Engineers began work on the project in 1948. Early work included the relocation of towns, bridges, and roads that would eventually be flooded out. The dam was closed in 1958 and completed in 1961, and the reservoir was full for the first time in 1962. The power plant was completed in 1963. President John F. Kennedy attended the dam dedication ceremony on August 17, 1962.

The photos are a bit dark due to rapidly deteriorating weather conditions during my visit. The photo above is an attempt to capture the full width of the dam. The structure is almost exactly 2 miles from bluff to bluff. The photo below is a close-up view of the power plant water intake control towers. These towers contain valves that regulate the water flow into the tunnels that carry water under the dam to the power plant. Each steel-lined tunnel is 24-feet in diameter and is about 3,650 feet long. The water is approximately 200 feet deep in this area.

These two photos show the front and back sides of the dam. The photo above shows the back side of the dam and Lake Oahe. The normal water level is clearly visible in the rip-rap rock. The water is normally very high towards the end of the spring run-off, and the level drops though the fall and winter to maintain power generation and to ensure that there is enough water in the river for boat navigation below Sioux City, Iowa. The photo below shows the front side of the dam that is downriver to the structure. The dam is over 245 feet tall compared with the original river level.

The photo above is a view of the power plant, power substation, and the river outflow channel. The power plant has 14 large tanks on the roof in two rows of 7. These are surge tanks, which act as buffers to smooth out the flow of water from the intakes. The 7 turbines that produce a total of 112-megawatts of electrical power.

The photo below is looking west along the highway that runs across the top of the dam. The bluffs on the far side of the dam are about 1-1/2 miles in the distance.

In the photo above, we continue to cross the Oahe Dam, heading west. We are just over halfway across the dam at this point.

The photo below shows the crane that operates the emergency spillway. The spillway allows water to exit the dam without going though the power plant. This would be done in the event of a large flood in order to prevent water from flowing over the top of the dam.

The photo above is view of the spillway structure from the base of the dam. The spillway and outflow tunnels are buried under the dam, so only this small concrete pad sticks up above the dam. The crane is used to operate each of the 8 Tainter gates. The gates are 50 feet wide by 24 feet tall, and are located 240 feet below the crane. Pairs of gates feed 4 outflow conduits which are nearly 20 feet in diameter and are approximately 3,500 feet long.

The photo below is a view looking towards the top of the dam from a service road at the base of the dam. The top of the dam is 245 feet tall. The face is covered with grass to prevent erosion. The grass is mowed regularly to make wet spots more visible so they can be inspected and fixed more quickly. Note that a team is running a drill rig in this photo, which is another type of routine inspection that is performed on the Oahe Dam.