Wealthy Seattle suburb ordered to boil water over E. coli; no one sickened on Mercer Island

Residents told to boil drinking water for the second time in a week because of E. coli contamination are awaiting new test results Friday in the Seattle suburb of Mercer Island — one of the wealthiest towns in Washington state whose residents include billionaire Microsoft co-founder Paul Allen.

The warning is unusual because most boil-water advisories hit small communities in rural areas. The city on an island in Lake Washington issued the second order Thursday after routine testing again turned up E. coli, and more than 60 businesses were told to close. An advisory last weekend was lifted Monday after shuttering schools and restaurants.

More chlorine is being added to the water — enough to make tap water smell like a swimming pool — and officials hoped to announce Friday whether samples are clean of the bacteria.

There have been no reports of illness. 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.

Local and state health officials at a news conference Thursday said they don't know how the E. coli is getting into the water. They thought it was a random minor incident that was cleared up Monday when samples came back clean after the first boil-water advisory.

Meanwhile, Mercer Island schools remained open Friday by using bottled water, "heat and eat" meals and temporary washing stations in the restrooms. Teachers could use the incident as a learning opportunity to talk about millions of people around the world who do not have access to drinkable water, District Superintendent Gary Plano said in a statement.

Some of the 62 restaurants, coffee shops and delis that were ordered to close could reopen with prepackaged food under the observation of the Seattle-King County Health Department.

Mercer Island has increased water sampling and inspections of construction sites in an attempt to find the source of the contamination. In addition to adding extra chlorine, crews are flushing water mains in potential problem areas. The city is asking residents to report if garden irrigation systems were connected without a backflow preventer.

With a population of 24,000 and many waterfront homes on the 6-square-mile island, the city 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.