Blackmans Lake Management

The Blackmans Lake Cyanobacteria Management Plan is a strategic approach to address and manage cyanobacteria-related issues at Blackmans Lake, aimed at preserving water quality and ecosystem health. 

Blackmans Lake has experienced blue-green algae blooms over the past years. Blue green algae is capable of producing toxins which can cause serious illness in people and pets that come into contact with affected water. The blue-green algae bloom looks like blue or green paint floating on the surface. Signs are posted at the parks and a notification is posted on the City website when a blue-green algae bloom is identified at Blackmans Lake.  Lake users should avoid contact with the water and keep pets away from the lake when it is experiencing a blue-green algae bloom. 

In 2022, the City Council authorized a contract with Herrera Environmental Consultants, Inc. (Herrera) to complete the Blackmans Lake Cyanobacteria Management Plan (Plan) to address blue green algae.  In 2022 and 2023, Herrera coordinated water sampling with volunteers, Snohomish County Lakes Division, and the City at Blackmans Lake as part of the Plan.  On May 20, 2024, Herrera presented their findings and recommendations to address the blue-green algae blooms based on site visits, and the analysis and review of the data from the Blackmans Lake water samples.  

Below are links to the May 20, 2024, presentation slides and Quality Assurance Project Plan. 

Herrera will present the draft plan to Council on July 16, 2024. The presentation will include a discussion on the data analysis and recommendations. Below is a link to the draft plan. 

Please send questions to Yoshihiro Monzaki, City Engineer at monzaki@snohomishwa.gov.