Health officials have advised customers of Island Utility Water System – which serves the southeast portion of the island – to boil their tap water before drinking, following recent water samples in which traces of the E. coli bacteria were found.

The island is served by several different water systems, but only customers of Island Utility — which serves 146 connections and about 1,230 islanders, including Port Blakely Elementary and IslandWood schools — need to boil their water, said Denise Lahmann, of the state Department of Health. It is believed that only the two schools, which have a separate connection, were actually contaminated, but Island Utility went door-to-door Sunday afternoon and evening to notify residential customers as well, said company spokesperson Scott Shelton.

Island Utility’s service area stretches from Restoration Point to Old Mill Road and across portions of Blakely Avenue and West Blakely.

It is a privately owned water company not affiliated with other water systems in the area, and is not part of the city system.

“We consider it fortunate that only a limited area was affected,” Shelton said. “The terrible thing is that two schools are located in that area. We are extremely concerned and are doing everything we can to eliminate the bacteria from the water system.”

The positive test was first discovered on Friday evening, but couldn’t be confirmed until Sunday because samples must incubate before they can yield results.

For safety, customers should only use treated bottled water or boiled water for consumption, brushing teeth, dishwashing, preparing food or making ice. Water should be boiled for 3 to 5 minutes and allowed to cool before using.

The advisory will be in effect until at least tomorrow afternoon, when the next round of test results are expected, but customers should heed the warning until further notice.

Neither Island Utility nor the health department know for certain what caused the contamination, but it is believed to be the result of recent “surface water intrusion” caused by heavy rain.

No illnesses related to the consumption of contaminated drinking water have been reported. To correct the problem, water system operators are inspecting the system to identify potential contaminant entry points, raising disinfectant levels and flushing water through the system.

Lahmann, whose agency is working with Island Utility to correct the problem, said people should boil water rather than using personal water filtration systems because, if stormwater is indeed the culprit, there could be other contaminants present that haven’t been tested for.

“If you look at a puddle, E. coli isn’t the only thing in there you wouldn’t want to drink,” she said. “I’m not saying for sure there are other contaminants present, but without testing we just don’t know.”

Once test results are reported safe, customers will be notified by Island Utility that the advisory has been lifted.

Other information and publications about drinking water and coliform bacteria are available on the Department of Health web site (www.doh.wa.gov/ehp/dw).

For any questions customers may have, contact Scott Shelton at 206-484-8317 (cell phone) or 206-319-2656 (office).