Localized HCB found in Boysen Reservoir, not affecting Boysen Marina

    On August 28, 2019, Boysen State Park reported a cyanobacterial bloom. The Wyoming Department of Health issued a recreational use advisory for Boysen Reservoir.

    With the upcoming holiday weekend, we reached out to Boysen Marina to confirm HCB is not affecting them and they confirmed it is not.

    What is HCB?


    HCBs are also referred to as harmful algal blooms (HABs) since cyanobacteria are commonly known as blue-green algae. The Department of Health issues advisories to inform the public that there may be health risks for people and animals in areas where HCBs occur.

    What does ‘recreational use advisory’ mean?

    Lakes and reservoirs under a recreational use advisory are not closed since HCBs may only be present in certain areas of the waterbody and conditions can change frequently. The advisory will remain in place until the bloom has fully dissipated.

    Which areas of Boysen Reservoir are affected? The most up-to-date information, as well as other HCB resources, can be found at

    • northern swim beach of Boysen Reservoir
    • Fremont Bay
    • eastern coves of the reservoir

    What else should I know?

    The Wyoming Department of Health and Wyoming Livestock Board recommend the following:

    • Avoid contact with water in the vicinity of the bloom, especially in areas where cyanobacteria are dense and form scums.
    • Do not ingest water from the bloom. Boiling, filtration and/or other treatments will not remove toxins.
    • Rinse fish with clean water and eat only the fillet portion.
    • Avoid water spray from the bloom.
    • Do not allow pets or livestock to drink water near the bloom, eat bloom material, or lick fur after contact.
    • If people, pets, or livestock come into contact with a bloom, rinse off with clean water as soon as possible and contact a doctor or veterinarian.

    Questions about health effects and recreational use advisories can be directed to Dr. Karl Musgrave, State Environmental Health Epidemiologist / State Public Health Veterinarian, Wyoming Department of Health, at [email protected] or (307) 777-5825.


    Questions regarding cyanobacteria sampling can be directed to Michael Thomas, Natural Resource Analyst, Wyoming Department of Environmental Quality, at [email protected] or (307) 777-2073, or Lindsay Patterson, Surface Water Quality Standards Coordinator, Wyoming Department of Environmental Quality, at [email protected] or (307) 777-7079.


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