Sewer utility crews responded Sunday morning to an overflow from King County’s South Mercer Pump Station.

An undetermined quantity of wastewater overflowed into Lake Washington for about 20 minutes from the station, which is located at the intersection of East Mercer Way and Southeast 72nd Street on Mercer Island.

The overflow was caused by a mechanical problem during a power outage. The issue was corrected shortly after by a worker who reported to the site. The station is now operating normally. Operations will continue to monitor the facility. King County will notify health and regulatory agencies, sample water quality and post signs warning people to avoid contact with the water over the next several days as a precaution to protect public health.