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Harmful Algae

Blue-green algae is common in Colorado. Hot weather and slow moving water such as in lakes and ponds can create conditions where algae can grow quickly and form a bloom. Some Blue-Green algal blooms produce toxins that can be harmful to pets, humans, and other animals that come into contact with the water. 

Signs of Blue-Green Algal BloomsSign warning residents to stay out of water

  • May look like thick pea soup or spilled paint on the water's surface.
  • Can create a thick mat of foam along the shoreline.
  • Usually are green or blue-green, although they can be brown, purple or white.
  • Sometimes are made up of small specks or blobs floating just at or below the water's surface.  

What the City is Doing

Arvada Reservoir is regularly tested for algae identification and counts along with other contaminants. Other city owned lakes and ponds are not tested unless they exhibit signs of algae blooms during routine site inspections. It is important to note these toxins can be very transient, present one day and gone the next. Testing can only confirm the current presence of algal toxins. Due to the transient nature of the toxins, public awareness, over subjective testing, becomes the key to minimize health risks. City staff will post additional signs at lakes and ponds that have tested positive for toxic algae.

What Residents Can Do

Swimming and off-leash dogs are prohibited at all City owned lakes and ponds in Arvada. We encourage City residents to obey all posted signs at lakes, ponds and realize the risk involved when not followed. 

The Environmental Protection Agency provides information on their website about the health effects from cyanotoxins and steps to take if you believe you have been exposed.