New closure and reopening protocols at King County’s lake beaches will better protect public health

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While the official start of summer is still a month away, King County starts monitoring water quality at popular lake beaches (in-language resources available) this week. This annual program helps protect the public’s health during the swim season.

We do this by tracking the water quality at more than two dozen beaches from mid-May to mid-September. The Department of Natural Resources and Parks, the King County Environmental Lab, and cities throughout the county all partner with Public Health.

Environmental scientists collect water samples from each beach every week throughout the swimming season. They test the water for bacteria. Our scientists look through the data for potential public health risks. Depending on the results, we close or open beaches to keep people safe.

We’re looking for bacteria that indicates there’s fecal pollution. “Fecal pollution” means poop, which contaminates the water and usually comes from people, pets, or wildlife such as geese. Poop carries germs that can make people sick if they get it into their mouths or cuts in their skin.

Image of a parent helping a child swim in a lake.

This year, we’re changing how we make beach closure and reopen decisions. These changes are in line with the latest science.

If you swim at King County beaches, this means you could see beach closure signs go up and down more often. But the signs will likely be up for shorter durations. And overall, we expect beaches will be open for about the same amount of time as under the old decision-making protocol.

Why did Public Health make this change?

The criteria we’ve been using to close and reopen beaches are based on now-outdated scientific guidelines. They also led to conservative decisions. It took a lot of tests showing poor quality to close a beach. It then took a lot of tests showing good water quality to open a beach.

Our new standards are based more on the real-time water quality data that we get each week. So, when water quality gets worse at a beach, it’ll close more quickly. When water quality improves, the beach will open faster.

What does this mean for you?

Since beaches may close and reopen more quickly, check out our Lake Beach website (in-language resources available) to find out if the beach you want to visit is open.

We can all help keep the water free from harmful bacteria:

  • Don’t feed geese and ducks near the beach – feeding them makes them poop, which makes the water quality worse.
  • Always shower before swimming. People can carry bacteria on their bodies that will get into the water. This makes showering before important! Also, showering after swimming can help protect you from any bacteria that may already be in the water.
  • Make sure babies and toddlers wear good-quality swim diapers.
  • Report water quality concerns to your local parks department.

Stay safe while swimming.

  • Swim in lifeguarded areas.
  • This time of year, the water is cold enough that jumping in can cause your body to go into shock. This can cause drowning and death – even if you are a strong swimmer! If you’re swimming, playing, or boating in a lake or river, wear a lifejacket – especially if there isn’t a lifeguard.
  • Use this map to find an affordable lifejacket near you (this webpage is in English only)
  • Learn more about swim safety on our Water Safety webpages (this webpage is in English only).

Originally Published 5/16/2023.