Notable Dam Failures
Despite our best efforts to promote dam safety and assist owners in maintaining their dams in a safe manner, failures sometimes occur.
Reasons for dam failures include:
The following table and paragraphs describe some recent dam failures in Washington and the lessons learned.
Notable Dam Failures and Incidents In Washington State - a table that includes: project name, location, date of Failure, number of lives lost, nature of failure and damage.
Seminary Hill Reservoir failed in October 1991 due to a massive landslide beneath the embankment. 3.5 million gallons were released in less than 3 minutes flooding a residential area.
The concrete overflow spillway had been modified to increase the storage of the reservoir, however this reduced the discharge capacity some 70 percent from the original design. The dam failed by overtopping during a flood in 1989.
The Iowa Beef Processors Waste Lagoon failed when snowmelt in the area adjacent to the lagoon raised the water level to near the crest of the dam. Effluent flowed into animal holes near the crest and initiated an erosive breach. Over 270 acre feet of waste effluent were released downstream and washed out a railroad line causing a train to derail. The effluent was contained in another waste lagoon owned by a paper mill just upstream of the Columbia River narrowly averting an environmental disaster.
This failure occurred in July of 1995 due to erosive piping of the embankment materials along the outlet conduit. The reservoir was partially lined with a PVC liner, however, seepage passed beneath the liner and initiated the failure.
A 20 foot diameter sink hole appeared on the dam crest in December of 1996. A section of the drop inlet conduit running beneath the dam collapsed, resulting in embankment material being sluiced out through the break.
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