Industrial History: 1931 Bagnell Dam on Osage River creates Lake of the Ozarks

Monday, April 3, 2023

1931 Bagnell Dam on Osage River creates Lake of the Ozarks

I've heard of the Lake of the Ozarks as a tourist destination. When I learned that the river spanned by the US-65 bridge was called the Lake of the Ozarks, I decided to investigate. When I saw that the bridge was just downstream from the Truman Lake Dam, I figured the river at Warsaw was the upper reach of a reservoir for a downstream dam. So I looked for that dam and found this one.

cdm_2179, Courtesy of the Missouri State Archives

cdm_2173, Courtesy of the Missouri State Archives

Ameren

- Bagnell Dam was the largest - and last - major dam in the U.S. to be built with private investment.
- Bagnell Dam is one-half mile long, rising 148 feet high from bedrock. That’s comparable to a building 12 stories high and seven blocks long. It holds back 600 billion gallons of water.
- Ameren Missouri invested $53 million in upgrades at Bagnell Dam in 2017 and 2018, including 67 post-tensioned anchors and more than 66 million pounds of new concrete to weigh down the dam and secure it into the bedrock.
- Missouri’s Lake of the Ozarks is one of the largest man-made lakes in the world, covering 86 square miles in four counties. [It was the largest man-made lake in the USA when it was created.]

Ameren
It was the only major construction project in the country after the stock market crashed two months after work began on the dam. It started producing power on Oct 16, 1931, just two years after construction began. [Below is a source that says it was completed in 18.5 months.]

MargaritaVilleRestortLakeOfTheOzarks

sos, Courtesy of the Missouri State Archives
"The Lake of the Ozarks is one of the largest man-made lakes in the United States. With a surface area of 55,000 acres, stretching 92 miles from end to end, and over 1,150 miles of shoreline, this lake brings in millions of dollars in tourism to Missouri each year."
A collection of 845 photographs

Kathy Heintz Powell posted two photos with the comment: "Bagnell Dam Osage Hydro Plant at Lake Ozark, MO. My work home for 36 years of the almost 41 years with Ameren."

It looks like they first built every other bay.

cdm_2586, Courtesy of the Missouri State Archives
Image showing the view looking west from the north east corner of the spillway cofferdam.

This photo confirms that they started with alternating bays.

cdm_2773, Courtesy of the Missouri State Archives
Image showing an upstream view of the spillway.

MillerCountyMuseum
"The dam is of concrete gravity type, 2,543 feet long. It consists of a 511 foot long power station, 520 foot long spillway section and two non-overflow retaining sections adjacent to the river banks. The dam supports a concrete highway structure, which includes a 20 foot wide roadway and a three foot wide sidewalk, both spanning the entire length of the dam."

MillerCountyMuseum, CityOfLakeOzark has the same information.
The power company that built this dam also operated the Keokuk Dam.
"The accomplishments achieved during the building of Bagnell Dam are incredible. When added to the fact that the project was completed in 18 ½ months, four months ahead of schedule, they become nearly incomprehensible."
In addition to the dam and transmission lines, roads and a village for the workers also had to be built.
[The article has a detailed timeline of the construction.]