The health threat came on a spring-like Sunday that drew a lot of families to the waterfront - their outing spoiled by raw sewage.
The Barton pump station, right next to the Fauntleroy ferry dock, blew a cap on Saturday night. King County crews don't yet know how much sewage spilled into Puget Sound.
That was no comfort for Nicole Grant and her family, who had been looking forward to spending the afternoon along the waterfront.
"What a shame," she says.
The county considers the spill enough of a threat to post signs warning people to stay out of the water and avoid possible exposure to fecal coliform.
"That's horrible because we were planning on enjoying low tide today, and looking for some critters," said Grant.
Neighbors remember a power outage caused a similar overflow last summer. It makes taxpayers wonder - what's going on?
"Sewage spill - I mean that sounds like something that could have been prevented, probably," says James Shively, who was visiting the beach.
Construction is under way to do just that. The pump station is getting a multimillion-dollar upgrade - new electrical work, back-up generators and expanded wastewater capacity from 22 million gallons a day to 33 million gallons.
"The original capacity wasn't enough. We need more capacity. And they're adding vast quantities of capacity to handle it. So that works for me," says local neighbor Martin Westerman.
Some of King County's sewage pipes are a century old. Maintenance - and replacing parts - is an ongoing job, dependent on the budget.
It's not something families on a Sunday afternoon want to worry about. But after this latest spill. - they do.
"I think I'm going to warn my children not to touch the water," says Grant.