Psych! Gene Coulon Beach is closed again to swimming | May 26

Published 4:35 pm Wednesday, May 27, 2026

Just when you thought it was safe to go back in the water, the county declares Gene Coulon Beach to once again be unsafe for swimming.

For the second time this month, and less than a week since being open for swimmers, King County has declared that the water at Gene Coulon Beach — the most southern swimming beach in Lake Washington — has bacteria levels that are too high.

According to May 26 tests, the water samples at Gene Coulon show that 2/3 of the sampled areas are over 320 colony forming units (CFU) per 100 milliliters of sample water (>320 CFU/100 mL). CFU is a count of the number of bacteria, per 100 milliliters.

While Sample B shows 230 CFU/100 ml in one area, which is low, Sample A shows 350 CFU/100 mL and Sample C reveals 690 CFU/100 mL.

Due to these high bacteria levels, the county says that people should stay out of the water if they do not want to get sick.

Last week, the average CFU of bacteria tested on May 18 showed 27.66 CFU/100 mL. The prior week, and the first testing of the year, showed that the bacteria tested on May 11 was particularly high at an average of 5,033.33 CFU/100 mL, with Bacteria Sample C clocking in at 14,000 CFU/100 mL.

The water at more than two dozen lake beaches that are popular swimming spots are regularly tested for bacteria every year from mid-May to mid-September.

If water tests find high CFU, it means that there are high levels of biological waste from people, pets, or wildlife in the water, which can carry germs that make people ill.

Houghton Beach, Matthews Beach, Newcastle Beach and Pritchard Island Beach are also currently closed due to high bacteria levels.

What the county does once a beach is closed

The county first tries to find the source of the high bacteria, which means finding the source of waste getting into the water. Additional testing may be utilized along with contacting local sewage utilities about possible sewage leaks and spills.

When the source of the high bacteria levels are determined, the county will work with beach managers to keep poop out of the water, allowing swimmers to eventually return.

According to the county website, beach managers will be advised to do the following:

• Remind people that dogs are not allowed at the swimming beach, and geese and ducks should not be fed near the beach.

• Clean up goose poop from docks to keep it out of the water at the swimming area.

• Reduce the number of geese near the beach, by using shiny mylar strips (“scare tape”) or specially trained dogs.

• Renovate docks to allow more water circulation through the beach area.

• Improve drainage in the park area near the beach, to reduce bacteria washing into the lake near the beach.

• Reduce poop getting into streams near beaches.

To learn more about King County’s swimming beach data, visit kingcounty.gov/en/dept/dnrp/nature-recreation/parks-recreation/king-county-parks/water-recreation/swimming-beach-bacteria-temperature.