More King County beaches closed due to contamination, now 8 total
Sep 17, 2025, 3:01 PM
A "NO SWIMMING" flag flies. (Photo: Mark Wilson, Getty Images)
(Photo: Mark Wilson, Getty Images)
As the region’s summer nears its close, health officials warned that several King County beaches have returned high bacteria samples, and beachgoers are urged to stay out of the water.
High bacteria and toxic algae detections were found at Madison Park Beach, Houghton Beach, Gene Coulon Beach, Newcastle Beach, Echo Lake Beach, Cottage Lake, Green Lake East, and West Beach.
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High bacteria levels at multiple King County beaches
King County Public Health (KCPH) collected three water samples in separate parts of each beach on Sept. 9, 15, and 16, which recorded high bacteria levels.
“We test the water for bacteria, which tells us whether there is poop in the water from people, pets, or wildlife. Poop can carry germs that can make people sick from swimming or playing in the water,” the agency wrote in a news release.
The health department based its decision on how many Colony Forming Units (CFU) were found, which is a count of the number of bacteria per 100 mL of water (about a half-cup of water), according to King County.
A beach is deemed contaminated with bacteria if two or three samples return a result of more than 320 CFUs on the same day.
- Madison Park Beach: Sample A, 760
- Houghton Beach: Sample A, 700; Sample B, 500; Sample C, 720
- Gene Coulon Beach: Sample B, 340; Sample C, 390
- Newcastle Beach: Sample B, 330
- Echo Lake Beach: Toxic Algae
- Cottage Lake: Toxic Algae
- Green Lake Beach East: Toxic Algae
- Green Lake Beach West: Toxic Algae
Newcastle Beach previously tested 13x higher than safety levels
On Sept. 9, Newcastle Beach recorded two bacteria samples noticeably higher than the KCPH 320 CFU threshold. Sample A revealed 2500 CFUs, which were eight times higher than King County’s baseline for a contaminated beach, while Sample B reported 4100 CFUs, which was nearly 13 times higher.
“We use the bacteria test results to predict the chance that people will get sick from germs that might be in the water. There are many different types of germs that can come from poop (bacteria, viruses, parasites, etc.), and it is not possible to test for each one,” King County Public Health wrote. “Instead, we test for one type of bacteria that is easy to measure and is commonly used to predict the risk of getting sick from swimming.”
The summer heat ramped back up this week, reaching high 80s in parts of the greater Seattle area on Tuesday. Using a local beach to cool off from the heat is limited, but not completely out of the picture.
Beaches that remain open for public use include Madrona Beach, Seward Park, Magnuson Beach, Meydenbaur Beach, and Enatai Beach, among others.
There is no information on how long the closures will be in effect.
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