MERCER ISLAND, Wash. – Residents of a wealthy Seattle suburb were told to boil their drinking water through the weekend despite 15 new water samples testing clean of E. coli contamination Friday.
It was the second time in a week people were ordered to take precautions with tap water in Mercer Island, a city of 24,000 on an island in Lake Washington whose residents include billionaire Microsoft co-founder Paul Allen. The warning is unusual because most boil-water advisories hit small communities in rural areas.
More than 60 businesses were told to close Thursday after routine testing again turned up E. coli. An advisory last weekend was lifted Monday after shuttering schools and restaurants.
Health and utility inspectors have not been able to find the source of the bacteria, and the city is considering sending divers to check its two closed water tanks, Mercer Island spokesman Ross Freeman said Friday.
If daily samples continue to test free of E. coli, the earliest the boil advisory could be lifted would be Monday, he said. No one has been sickened by the bacteria.
Mercer Island gets its water from Seattle Public Utilities through a pipe along the Interstate 90 bridge, but no E. coli has been found in other parts of the Seattle water system.
The city has been flushing water mains and adding chlorine — enough to make tap water smell like a swimming pool.
“This could happen to anybody, that’s for sure,” Freeman said. “We still have a top-notch water supply system. This is a very unusual case.”
Officials thought it was an isolated problem last weekend when the first boil advisory was issued.
“I’d say implementation was a bit of a hiccup,” said Nels Blair, a physics teacher at the city’s Northwest Yeshiva High School. “It didn’t go the way anybody really wanted it to go.”
That advisory was lifted Monday but a second one was issued Thursday when more E. coli showed up in a sample.
“Instructors told students who were using the bathroom not to touch the sinks, and if they filled a water bottle from a fountain, they should throw the bottle away or wash it with bleach,” Blair said.
Mercer Island public schools remained open Friday by using bottled water, “heat and eat” meals and temporary washing stations in the restrooms.
Some of the restaurants and shops forced to close again Thursday could reopen with prepackaged food under the observation of the Seattle-King County Health Department, the city said.
The city is distributing free water bottles at the Mercer Island Community Center, and volunteers are taking cases to institutions and vulnerable residents.
The presence of E. coli in a drinking-water sample usually indicates recent fecal contamination, health officials said. Most E. coli bacteria are harmless and exist in the intestines of people and warm-blooded animals.
Anyone who drinks contaminated water could become ill, but infants, young children, the elderly and people with compromised immune systems are at increased risk. Symptoms include diarrhea and vomiting that may last several days.
The city of Mercer Island encompasses the 6-square-mile island and has a median household income of more than $127,000, according to census data for the ZIP code in 2012. The state median household income is about $59,000.