Power Failure Leads to Sewage Spill in Washington

Event Year: 2010 Reliability: Confirmed
Country: United States
Industry Type: Water/Waste Water

A power failure shut down water-treating equipment at the Mabton water treatment plant.  A computer designed to detect loss of power failed to operate.  As a result, it failed to automatically switch the plant to a back up generator and alert the plant operator. The problem went undetected for two days.  By that time, 370,000 gallons of raw sewage had been dumped into the Yakima River.  Joye Redfield-Wilder, a spokeswoman for the state Department of Ecology said that it’s probably the largest municipal waste water accident in Eastern Washington in the past 20 years.


A computer system failed to detect the loss of power at the Mabton water treatment plant.  The back up generator was not automatically switched on as expected. 370,000 gallons of raw sewage spilled into the Yakima River.  The spill did not affect drinking water or hurt the wildlife.  The river quickly diluted the sewage.  However, the spill could have exposed people to E.coli, parasites, bacteria and viurses that cause nausea and diarrhea and other stomach problems, a few of them fatal.