Gene Coulon Beach closes for 4th time this year | July 13

Published 10:55 am Wednesday, July 15, 2026

Despite Renton River Days being right around the corner, the county has announced that Gene Coulon Beach is again unsafe for swimmers.

For the fourth time this year, and a few weeks since being re-opened, the water at the most southern swimming beach in Lake Washington has been declared to have bacteria levels that are too high.

According to tests conducted on July 13, the water samples at Gene Coulon show that 1/3 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 A and B show low levels at 45 CFU/100 ml and 85 CFU/100 mL, Sample C revealed 420 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.

The first testing of the year on May 11, showed that the tested bacteria 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 and Mount Baker Beach are also currently closed due to high bacteria levels. Lake Marcel is currently closed due to toxic algae.

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.