Echo Lake has toxic algae bloom - people and pets should stay away from contact with the water

Saturday, September 22, 2012

Cyanobacteria algae bloom
Photo from USGS (not taken locally)

Algae bloom closes Echo Lake beaches

On Friday, September 14, the City’s water quality specialists sampled an algae bloom at Echo Lake.

The sample was sent to the state for testing. On Monday, September 17, the City was notified that the bloom was toxic.

City staff responded to the notification immediately by posting public beach closure signs in the following locations:

  1. Two notifications at the swimming beach area, one near the inlet and another to the south access area.
  2. One notification at the south end, at the dock access/boardwalk near the YMCA.

The City will be monitoring the bloom weekly, beginning Monday, until the bloom is no longer a threat. The beach closure will remain in effect until that time.

City’s Monitoring
The swimming beach monitoring program samples for toxic algae near the swimming beach on Echo Lake every other week. It also provides for opportunistic sampling anywhere on the lake and any time that a bloom is noticed.

Algae Blooms
The algae blooms of concern are commonly known as blue-green algae, or cyanobacteria. 

Blooms are a result of a combination of high nutrient levels, combined with warm temperatures and stagnant water. (Common sources of excess nutrients can come from fertilizers and mammal waste.)

There are many types of cyanobacteria and some produce toxins that are poisonous to mammals. The toxin we have tested positive for in Echo Lake is microcystins, a liver toxin (NOT a nerve toxin).

People and pets should avoid ingesting and coming into contact with the water. It can cause serious illness. If a pet or skin comes in contact, wash the exposed area. If an animal becomes sick, the pet should be taken to the vet. People should seek medical attention if they ingest water and then become ill.

King County provides an overview of monitoring and the toxin

Beach Closure Determination

The Department of Health (DOH) has set a 3-tier standard for beach closures:

  • Tier 1: There might be a problem, Caution signs posted;
  • Tier 2: Samples show microcystins above 6ug/L, Warning signs posted; and
  • Tier 3: A severe danger is determined to exist by DOH, Danger signs posted.


Our sample came back at 42.00 ug/L, which is a Tier 2 level.

More information can be found here


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