King County crews have stopped and contained a sewer overflow on north Mercer Island, and health officials are advising people to avoid contact with nearby water through Feb. 15, according to King County and the City of Mercer Island.
The overflow began Saturday evening, Feb. 7, and was stopped and contained at about 1:15 a.m. Sunday, Feb. 8.
Public Health – Seattle & King County is advising the public to avoid contact with potentially contaminated water in the area until 1:15 a.m. on Sunday, Feb. 15, or until the advisory is lifted.
The King County Environmental Lab collected the first set of water quality samples Sunday morning.
King County’s Wastewater Treatment Division said an initial investigation found that a temporary bypass system collapsed near the intersection of Fortuna Drive and North Mercer Way.
The collapse caused wastewater to back up and overflow from a maintenance hole.
The bypass system was installed as part of the North Mercer Island/Enatai Sewer Upgrade Project, which involves replacing aging sewer pipes.
By noon Sunday, the construction contractor completed repairs and restored normal operations at the site, according to King County.
Cleanup efforts are continuing in the area, including disinfecting portions of the I-90 Trail, nearby vegetation and storm drains where untreated sewage made contact.
A section of the I-90 Trail at Fortuna Drive remains closed during the cleanup.
North Mercer Way at the site has been reduced to one lane, with a flagger directing vehicle and bicycle traffic.
The City of Mercer Island first responded to reports of the overflow around 5 p.m. Saturday.
Wastewater Treatment Division crews arrived at about 7:45 p.m. Regulatory agencies have been notified.
King County’s Community Services team has posted warning signs in public access areas and notified nearby neighbors and businesses in person and by email.
Officials are asking the public not to approach workers at the site.
Anyone with questions or concerns can call the Community Services Incident Response hotline at 206-296-7432 and leave a message for a return call.