Snohomish’s Blackman Lake under toxic algae watch

Blackman Lake under toxic algae watch

SNOHOMISH — Toxic blue-green algae spotted on Blackman Lake on Monday, July 25, prompted the city to put up warning signs against swimming in the water.
Another round of sample testing is scheduled for this week, city spokeswoman Shari Ireton said.
Until the lake is determined safe, the city asks that people exercise caution. Pets should also be kept outside and any fish caught for eating should be thoroughly cleaned.
Yellow warning signs about 12 inches by 18 inches, about the size of the first page of a Grandstand newspaper, are displayed at Hill Park and Ferguson Park. In Hill Park, they are displayed at the entrance to the two fishing piers and on a lake watershed information kiosk.
Two sets of samples taken Sunday, July 24 for lab testing showed toxin levels within state recreation guidelines.
One sample recorded toxoids of 0.019 micrograms per litre. The state recreational guideline is no more than 1,000 micrograms per liter.
Toxic blue-green algae sometimes looks like paint spilled on water. Non-toxic algae look like a carpet.
Anyone can report an algae bloom at
The lake is often treated to control algal blooms and invasive water lilies.
The lake last received aquatic pesticide treatment on June 29, a spokeswoman for the state Department of Ecology said. It was an application to 1.25 acres of the 61-acre lake that was “treated with 32 ounces of Imazapyr to control non-native water lilies,” a second ecology spokesperson said.
Imazapyr is a non-selective herbicide; non-selective, meaning it kills any plant it comes in contact with.
Strict environmental permit controls regulate pesticide applications.
A future treatment should take place before September 30, Ecology said.
In 2021, Blackman Lake received three such treatments.

In related news

The city is looking to hire a diver to manually remove invasive weeds from curly leaf ponds in the lake this year. This weed was first spotted in the lake in 2021.

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