The Lincoln Memorial Reflecting Pool on the National Mall turned green after being refilled following a recent repainting and renovation, prompting Interior Department crews to deploy cleanup measures.
Rosalina Stancheva Christova, a professor of aquatic ecology at George Mason University, took water samples and confirmed the algae belongs to the genus Desmodesmus, which she said was "growing in excessive amounts" and is not toxic or harmful.
Steve Goodale, a Canadian swimming pool specialist known online as "Swimming Pool Steve," said, "It's called 'New Pond Syndrome,'" and described the phenomenon as common when a natural, clear body of water is restarted in an open-air environment.
Christova said last month's renovations may have disturbed the pool and affected the balance of nutrients, potentially accelerating the blooms, and Goodale said the pool's new, darker interior surface "is going to absorb more sunlight" and "result in water that's warmer," which can promote more prolific algae growth.
The Interior Department said workers have poured hydrogen peroxide into the water and deployed "high-tech nanobubble ozone technology" to neutralize algae, calling hydrogen peroxide a "milder treatment than chlorine" and saying there are "no harmful side effects to marine life or to the environment."
Goodale said the nanobubble ozone bubbles are so tiny the human eye can't see them and described them as "neutrally buoyant," saying "they can last for weeks, if not months in the water, doing their oxidizing thing."
Federal contracting records show an Ohio-based company, Green Water Solutions, received a $1.7 million no-bid contract to install a Nano Bubble filtration system at the Reflecting Pool, and the company's owner is listed on those documents as "JJ Cafaro Investment Trust," with John J. Cafaro identified as president and CEO on Federal Election Commission filings.
Records identify John J. Cafaro as having donated to several GOP candidates and conservative causes, giving $250,000 to the Trump Victory fundraising committee in 2020, and show he pleaded guilty to campaign finance violations in 2010 and earlier pleaded guilty to conspiring to bribe Rep. James Traficant; documents also show he and his wife own a home in Palm Beach.
Federal contracting documents cited a contracting rule for projects of "unusual and compelling urgency," pointing to the need to fix the Reflecting Pool in time for the nation's 250th birthday on July 4, and described the Nano Bubble system as a "highly specialized and niche technology with limited domestic suppliers."
The scope of the project expanded during the work, with the cost growing from an initial $2 million price tag to at least $14 million, and federal contract records show a separate $14.7 million no-bid contract to Atlantic Industrial Coatings to install sealant on the pool floor.
Workers were seen vacuuming dead algae, deploying mobile vacuuming "trash pumps," standing in the pool with long-handled vacuums and marking work zones with orange cones while passersby photographed the water and peeling sections of paint.
Large flakes of paint were observed floating on the surface, and laboratory testing commissioned by a news outlet identified the algae as Scenedesmus, even as Christova had identified it as Desmodesmus from her samples.
President Trump wrote on Truth Social that there had been "real problems with Vandalism" at the Reflecting Pool, alleged people had "done everything possible to hurt the inside surface," said the algae problem was "75% gone" and "will soon be completely remedied," and claimed law enforcement is "actively investigating this situation."
The Interior Department posted on X that the nanobubble technology had "very effectively killed the algae" and said National Park Service crews were "vacuuming up the dead algae resting on the bottom of some parts of the Reflecting Pool."
Christova said she would like to see the water monitored weekly, warning that "If we don't have any control over algal growth, we don't know what is growing."