High bacteria levels close 5 King County beaches amid summer heat

As the summer heat remains in the 80s and 90s across the region, health officials warned that five King County beaches have returned high bacteria samples, urging beachgoers to stay out of the water.

High bacteria detections were found at Gene Coulon Memorial Beach, Juanita Beach, Lake Meridian Beach, Matthews Beach, and Waverly Beach, Public Health — Seattle and King County announced.

High bacteria levels at 5 King County beaches

Public Health collected three water samples from separate parts of each beach on June 15, and the samples recorded high bacterial levels at each beach.

“We test the water for bacteria, which tells us whether there is poop in the water from people, pets, or wildlife,” the department stated. “Poop can carry germs that can make people sick from swimming or playing in the water.”

Public Health based its decision on the number of colony-forming units (CFU) found, which is a count of bacteria per 100 mL of water (about half a cup), 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, or if there are two or more high bacteria samples at a beach in the last 30 days.

The following list includes beach samples with elevated bacterial CFUs:

• Gene Coulon Memorial Beach: Sample C, 670
• Juanita Beach: Sample A, 400
• Lake Meridian Beach: Sample C, 630
• Matthews Beach: Sample B, 590
• Waverly Beach: Sample A, 750; Sample B, 400

“We use the bacteria test results to predict the chance that people will get sick from germs that might be in the water. Many different types of germs can come from poop (bacteria, viruses, parasites, etc.), and it is not possible to test for each one,” 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.”

Other beaches remain open as temperatures remain in the 80s

The summer heat is expected to remain in the mid-80s to kick off the week, before temperatures drop as low as 65 degrees over the weekend. Options for cooling off at a local beach are limited, but not completely out of the picture.

Public Health noted that while a majority of beaches tested in the summers of 2020-2025 had good water quality at least 95% of the time, it is still recommended to check the Public Health beach bacteria map before spending a day at the beach.

Beaches that remain open for public use include Madrona Beach, Magnuson Beach, Meydenbauer Beach, and Luther Burbank Beach, among several others.

There is no information on how long the closures will be in effect.

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