Luther Burbank Park swim beach closed due to high bacteria levels

Published 9:30 am Thursday, August 21, 2025

Due to high bacteria levels, Public Health – Seattle & King County has closed the swim beach at Luther Burbank Park until further notice, according to a city of Mercer Island social media post on the evening of Aug. 20. The closure was effective immediately.

After receiving Public Health’s water test results that afternoon, the city said that all park visitors — including children and pets — should obey the posted closure signs and stay out of the water. King County will inform the city when water quality improves to safe levels for accessibility.

Public Health said that a reopening can potentially occur as early as next week, as soon as its testing shows low bacteria again. They conduct weekly water testing from mid-May through mid-September with the next testing set for Aug. 26; results will be available on Aug. 27.

Recently conducted Public Health water quality testing at Lake Washington swimming areas and other area lakes indicated higher than normal bacteria levels at the Luther Burbank swim site. Public Health regularly conducts these tests to ensure the water is healthy for beachgoers, the city said. The city noted that no testing is performed at the dog park or other water access points.

“Public Health tests Luther Burbank and Groveland Beach swim areas on a weekly basis. Groveland Beach bacteria counts are currently within safe levels. The bacteria counts in the water around Mercer Island are typically low. Increased water temperature due to the heat and recent heavy rains pushed contaminants into the lake, likely affecting water quality,” the city said.

Daniel Nidzgorski, ecologist with the King County Water and Land Resources Division, said that Public Health collected three water samples at Luther Burbank on the morning of Aug. 19. All three contained high bacteria.

“We don’t know the cause of the bacteria. We test for a common bacteria that’s found in the poop of all warm-blooded animals, including people, dogs, birds and other wildlife. Our field staff have noted dogs swimming in the water at Luther Burbank Beach multiple times this summer, so that’s one potential source. And goose poop is pretty common at many swimming beaches,” said Nidzgorski, adding that the lab tests take about 24 hours because they involve incubating the bacteria.

As soon as the test results were available, Public Health informed the city of Mercer Island of the situation. Public Health has not been informed of anyone affected by the bacteria at Luther Burbank. Nidzgorski said that most people don’t call the county if any issues arise.

To help reopen the beach and keep it that way, Nidzgorski said that people can lend a hand and “keep poop out of the water. Don’t bring your dog to the beach. The city of Mercer Island does not allow dogs at public swimming areas during the summer. And please don’t feed ducks or geese near the beach — more food attracts more birds, which leave more poop.”

At press time, the Public Health site noted that people were advised to refrain from entering the water at these other beaches because of high bacteria: Gene Coulon Beach (Renton), Houghton Beach (Kirkland), Idylwood Beach (Redmond) and Madison Park Beach (Seattle). Swimming is not allowed at Mount Baker Beach (Seattle), which had a sewage spill.

For more information and updates, visit: https://www.mercerisland.gov/parksrec/page/luther-burbank-swim-beach-closed

The Reporter will update this story when more information becomes available.