Gene Coulon Beach reopens for swimming | Aug. 12
Published 3:17 pm Wednesday, August 12, 2026
Two weeks after a fifth closure for the year, Gene Coulon Memorial Beach in Renton has reopened for swimming.
According to the King County website, the latest testing on Aug. 10 shows that Gene Coulon — the most southern swimming beach on Lake Washington — has lower levels of bacteria than the previous two weeks.
Data shows that all three sampled areas are below 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, and anything higher than 320 CFU/100 mL is considered a high level of bacteria and thus unsafe for swimming.
Sample A shows 19 CFU/100 mL, while Samples B and C came back with 43 CFU and 260 CFU.
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 (AKA poop) from people, pets or wildlife in the water, which can carry germs that make people ill.
On July 27, the beach closed for the fifth time where Sample A showed 260 CFU/100 mL, Sample B showed 240 CFU/100 mL and Sample C showed 360 CFU/100 mL. On Aug. 3, Samples A and B had gone down to 24 and 41 CFU/100 mL, but Sample C came back with 3,600 CFU/100 mL. The longest the beach park has stayed open for 2026 has been three weeks, from June 22 to July 12, before being closed down on July 13.
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.
