Dam and Disaster: The 1917 Mammoth Dam Break

Dams are a vital part of Utah's water infrastructure -- but they sometimes fail. A breach of the Mammoth Dam in 1917 sent millions of gallons of water rushing downstream, and exposed its poor conditions of construction and operation.

On June 24, 1917, the watchman at Mammoth Dam reported the reservoir's water levels were holding steady. He left for lunch and returned to a dramatically different scene: the dam had given way! The waters released by the dam failure were catastropic, sweeping away properties and threatening the lives and livelihoods of Carbon County's downstream communities. Makeshift conditions and inadequate operating procedures were just some of the all-too-common -- and preventable -- infrastructure issues that led to the Mammoth Dam failure.

The dam was initially built in 1902 on the Wasatch Plateau between Sanpete and Carbon Counties by the Price River Irrigation Company. By 1914, it was already up for renovations, but the reconstruction plans were never approved by the state engineer. Even still, the company was eager to store water and willing to overlook safety precautions in the process. With construction still underway, the company placed form boards around the top of the dam to accommodate increasing water levels. The rural, mostly immigrant population living in Carbon County communities downstream depended on Mammoth Dam, but had the most to lose by its failure.

When the watchman returned from his lunch on that June afternoon, he immediately called the dam caretaker for help. It took nearly two hours for the caretaker to arrive by horseback. Unfortunately, his desperate attempts to rescue the situation failed. The dam was entirely breached and a crushing force of millions of gallons of water was released downstream.

Thanks to early warning from the watchman, no lives were directly lost, although vulnerable residents of Scofield, Castle Gate, and Helper spent one scary night racing for higher ground ahead of the rushing waters. There were significant damages to property, crops, and business in the surrounding region, including nearly 30 miles of Denver & Rio Grande railroad track completely washed away.

Dams are central to Utah?s water infrastructure, but require maintenance. The shoddy upgrades to Mammoth Dam ultimately resulted in disaster and damage, and threatened the safety of Carbon County?s working class communities. It wasn?t until a series of nationwide dam failures in the 1970s that the federal government developed stronger dam safety regulations, hoping to protect those living downstream from aging infrastructure.