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City of Snohomish - NewsFlash

Posted on: August 2, 2018

CAUTION: Blackmans Lake Toxic Algae

Blackmans Lake Algea

Blackmans Lake is experiencing a blue-green algae bloom.

The bloom looks like blue-green clumps of algae near the surface of the water, and is particularly concentrated near the shorelines. Samples were collected on Wednesday, August 1st on the west shoreline by Snohomish County Surface Water Staff. Samples were taken to test for toxic algae but results will not be available until mid-next week. CAUTION signs are posted at Ferguson and Hill Parks.

The CAUTION signs advise lake users of the potential for exposure to toxic algae. It is especially important to avoid areas of algae scum because this is where the toxin levels are the highest. Also be aware that lake conditions and locations of scum can change from day to day.

CAUTION signs advise the following:Caution Sign - Blackmans Lake

  • Do not swim in areas of scum
  • Do not drink lake water
  • Keep pets away from the lake
  • Clean fish well and discard guts
  • Avoid areas of scum when boating


Toxic algae can cause serious illness in humans who drink or play in affected waters. Pets that drink the water are at particular risk. If you or your pet are exposed to a blue-green algae bloom and have unexplained sickness or signs of poisoning, call your health care provider or veterinarian.

Please click here to see up-to-date testing information, sign up for alerts, and answers to commonly asked questions (choose the “Toxic Algae” link from the main page).


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