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King County crews stop equipment malfunction and wastewater overflow at a Mercer Island pump station within 10 minutes


King County Wastewater Treatment crews this afternoon quickly stopped a wastewater spill into Lake Washington at a pump station north of Clarke Beach Park on Mercer Island.


King County Wastewater Treatment workers quickly stopped an equipment malfunction and subsequent wastewater spill into Lake Washington at about 12:19 p.m. today at the South Mercer Pump Station, restarting the pump within about 10 minutes.

The pump station, located north of Clarke Beach Park along Southeast 72nd Street on Mercer Island, is now operating normally.

Crew members posted caution signs along the water near the outfall and are testing water quality. 

King County reported the overflow to health and regulatory agencies. The amount of wastewater spilled and cause of the equipment malfunction are under investigation.

Update: The Wastewater Treatment Division issued the following update on March 25:

  • The beach at Clarke Beach Park has been reopened after consecutive days of quality testing confirmed that the water is safe. 
  • Staff members estimate that about 9,700 gallons of wastewater flowed into Lake Washington. 

Rachael Hartman, Wastewater Treatment Division, 206-477-4669