Despite our best efforts to promote dam safety and assist owners in maintaining their dams in a safe manner, incidents and failures sometimes occur. Here you’ll learn about the most recent dam safety incidents and failures, and also find information about historic events.
If conditions at a dam under our jurisdiction prompt an emergency declaration or the involvement of local/state emergency response staff, we track it here. This does not necessarily mean that a failure is imminent. In these cases, we work with local emergency management and the dam owner to take steps to reduce the risks posed by the dam.
Eightmile Lake Dam
Dec. 4, 2018
We are providing technical and regulatory support to reduce the risk posed by Eightmile Lake Dam in Chelan County. The dam is 90 years old and located in the Alpine Lakes Wilderness. After a 2017 wildfire, the area was left vulnerable to erosion, flash flooding, and possible dam failure. In spring 2018, the Chelan County Department of Emergency Management declared an emergency and led the response effort to notify local residents. Other involved agencies included the U.S. Forest Service and the National Weather Service.
The owner of the dam, the Icicle-Peshastin Irrigation Districts, completed repairs to the dam in summer 2018, including reshaping and armoring the dam crest and replacing part of the low-level outlet pipe. There is currently no elevated threat from the dam. We also installed monitoring equipment around the dam and conditions are normal.
Dam failures in Washington
Some incidents can lead to a catastrophic release of water which may cause loss of life, damage to property, and environmental harm. We refer to these events as failures. Below is a list of notable failures and some details on recent events.
Why dams fail
Nationally, the main reasons that dams fail are:
- Overtopping — 34 percent of all failures
- Inadequate spillway design
- Debris blocking the spillway
- Settlement of dam crest
- Foundation defects — 30 percent of all failures
- Differential settlement
- Sliding and slope instability
- High uplift pressures
- Uncontrolled foundation seepage
- Piping and seepage — 20 percent of all failures
- Internal erosion through the dam caused by seepage — "piping"
- Seepage and erosion along hydraulic structures, such as an outlet
- Conduits or spillways, or leakage through animal burrows
- Cracks in the dam
- Conduits and valves — 10 percent of all failures
- Piping of embankment material into conduit through joints or cracks
- Other — 6 percent of all failures