HELENA — The first Hauser Dam failed 114 years ago, causing a destructive flood and ultimately playing a large role in how dams were designed moving forward.
Hauser Dam on the Missouri River was named for Samuel Thomas Hauser, a former territorial governor of Montana. Built for $1.5 million by the Missouri River Power Company, construction began in 1905 on the first dam which was made from steel. The dam was declared operational on Feb. 12, 1907.
One issue engineers faced with construction was the riverbed at that section of the Missouri. The bedrock was covered by a thick layer of gravel, meaning it couldn’t be anchored in bedrock.
Steel sheet pilings were driven 35 feet into the riverbed and the steel of the dam was attached to the pilings. Stone footing capped with concrete on the upstream side was set against the pilings in the riverbed to support the structure. A 20-foot-deep layer of volcanic ash was laid down on the upstream riverbed to discourage seeping with engineers believing the weight of the water would compact it and prevent erosion around the pillars.
On April 14, 1908, at about 2:30 p.m. the dam failed after water pressure eroded away the ash and gravel by the footing of the pillars. Crews first noticed silt-heavy water gushing from the base of the dam which prompted them to evacuate the structure.
About 15 minutes later, the footings gave way, causing a breach in the dam. The water pouring through the breach further damaged the dam's footing, and six minutes later a 300-foot wide section of the dam tore loose.
A 20-30 foot wave swept downstream. Workers were able to notify people downstream, helping many get to safety in time. There were no officially reported deaths contributed to the dam’s failure. Damages were estimated at more than $1 million and pieces of metal that belong to the dam can still be found near the riverbanks downstream.
The first Hauser Dam was one of only three steel dams in the world. As a result of the dam’s failure, even though the steel was not found to be at fault, engineers saw the first Hauser Dam as a cautionary tale and no steel dam has been built since.
Missouri River Power began reconstruction of Hauser Dam in July 1908 and completed it in the spring of 1911.
Now owned by NorthWestern Energy, Hauser Dam can produce 19 megawatts of power.