Leaking water main forces evacuation of 20 homes on Mercer Island

Residents of 20 homes on Mercer Island, east of Seattle, were told to evacuate Wednesday night, due to risks of flooding or landslides. Now the city’s leaking water main has been shut off, and residents of six of those houses have permission to return.

At a briefing Thursday, City Manager Jessi Bon expressed her thanks to the residents for their cooperation.

“We were knocking on their doors around 9 o’clock last night asking them to leave — not the greatest time to be knocking on their doors, they were absolutely graceful, appreciative,” she said.

That happened after an engineer found unstable soil conditions around the water main situated uphill from those houses. The underground high-pressure pipe is owned and maintained by Seattle Public Utilities.

“There was a concern, and the reason that we evacuated homes, is that if the pipe were to break it could cause dangerous flooding or landside,” Bon said.

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It took several hours to drain the pipe and switch to a backup water main.

As of Thursday, “that pipe has been shut off, it has very little water in it right now, so that risk has been alleviated,” Bon said.

She said most evacuees stayed in hotel rooms in Bellevue. The city and the utility are funding their accommodations.

No word yet on when the leak will be repaired, or when the remaining residents can go home. They were allowed to return briefly Thursday to retrieve some belongings, city officials said.

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The city has switched to a backup water main, with no impacts to water pressure or quality, officials said.

Wylie Harper, director of water transmission and distribution for Seattle Public Utilities, said the cause and size of the leak aren't known yet.

“So the next steps in responding and addressing the leak are to excavate above the pipe and get eyes on where the water is leaking,” Harper said.