Prospect Lake closed until further notice due to presumed return of blue-green algae

The City of Colorado Springs has closed Prospect Lake in Memorial Park effective immediately and until further notice due to the presumed return of blue-green algae.

The closure follows a visual inspection by Parks, Recreation and Cultural Services (PRCS) staff and a water sample test by Colorado Springs Utilities on Wednesday, July 24. This test confirmed the presence of mycrocystin toxin, which is produced by cyanobacteria, also known as blue-green algae.

"It is always a difficult decision to close a popular recreational area especially in the middle of summer, but when it comes to the health and safety of the public, it is important that we take all the necessary precautions," said Erik Rodriguez, senior environmental, health and safety specialist for PRCS. "Algae blooms can produce toxins that can be harmful to humans and pets, so we decided to temporarily close the lake until the levels of algae are safe again."

Testing will be performed on a weekly basis with at least a required two-week closure to ensure the lake is up to the recreational water quality levels set by CDPHE and the EPA before the lake will reopen to the public.

Prospect Lake was closed in the summer of 2020 due to blue-green algae. Since that time, PRCS staff has taken proactive measures, including the application of an enzyme-based, non-pesticide treatment that consumes the biomass at the bottom of the lake and helps oxygenate the water. PRCS is also moving forward with Timberline Building Systems to install an aeration system in Prospect Lake tentatively scheduled in fall of 2024.

During the closure, the following activities are prohibited: swimming, bathing, paddle boarding, tubing, water skiing and non-motorized boating of any kind. No pets are allowed. Fishing areas will remain open, though anglers are urged to clean fish well and remove guts.

BLUE-GREEN ALGAE BACKGROUND

What is harmful algae?

Blue-green algae are a type of bacteria common in lakes throughout Colorado. When conditions are right, blue-green algae multiplies quickly. Those conditions include sustained hot weather, stagnant water, and polluted stormwater runoff.

These conditions result in too much nitrogen, potassium and phosphorus in the water. This causes the harmful bacteria to grow faster than the ecosystem can handle. The increased bacteria harm water quality, decrease the amount of oxygen available to animals living in the water, and can produce a toxin that is harmful to humans and pets.

Blue-green algae are self-limiting, naturally-occurring bacteria, which means it eventually phases itself out of bodies of water.

The Colorado Department of Public Health and Environment (CDPHE) offers additional information about blue-green algae on its website.

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