Where are the cleanest swimming areas in King County?

Sometimes water is clear. Sometimes water is murky with
evidence of plant life. How do you tell if the water
you’re about to hop into is clean?

King County monitors area swimming beaches weekly, May
through September, and the results of those weekly tests
are updated and available online.

The test samples come from popular lakes and swimming
beaches and are color-coded indicating “low concern” to
“high concern” based on the amount of fecal coliform and
algal toxins in the water.

Fecal coliform counts involve exactly what you think;
they’re intestinal bacteria from humans and other mammals
that can be found in water.

High levels of fecal coliform can indicate a sewage leak
or condition that heightens the health risk for people
swimming in the water. Small amounts of the bacteria are
routinely found in safe water, but high counts can lead to
warnings and beach closures.

There are currently no lake closures in King County, but
there are several creeks including John’s Creek, Juanita
Creek, Ravenna Creek, Idylwood Creek, and Thornton Creek,
that the county recommends avoiding at this time.

Closures of lakes and creeks can also result from the
presence of algal toxins. Toxic algae blooms have been
responsible for closures on Lake Sammamish and at Green
Lake in years past.

A particularly nasty type of bloom called cynobacteria,
that has been present in area lakes before, can sometimes
produce toxins that can be lethal to people and animals.
Poisoning from toxins can happen in 15 to 20 minutes and
may appear as numbness in the lips, fingers and toes, and
dizziness.

After a couple lake closures due to the blooms in the late
90s, cyanotoxin monitoring became a regular part of county
water safety checks.

Check the full list of King County lakes and
beaches for information on the cleanliness and safety
of water at swimming areas near you.

By JAMIE GRISWOLD, MyNorthwest.com Editor