Park Service continues to battle algae in renovated Reflecting Pool

The National Park Service (NPS) and Department of Interior (DOI) are actively treating algae blooms in the Lincoln Memorial Reflecting Pool, which discolored the landmark just days after a $15 million renovation. The DOI deployed hydrogen peroxide and nanobubble ozone technology to eliminate the algae, which turned the pool green and murky. Workers were seen dumping hydrogen peroxide into the pool, while rangers scraped algae from the bottom and siphoned contaminated water into storm drains. The algae was described as residual, stemming from reactivated supply lines after the renovation. The nanobubble ozone process releases tiny ozone-filled bubbles to kill algae and contaminants, with the DOI stating it poses no harm to marine life or the environment. A tubing system was installed to extract water and algae from the pool. The renovation, initially a $3.5 million project to resurface the pool for the U.S. 250th anniversary, expanded significantly in cost and scope. Greenwater Services, an Ohio-based water purification company, was hired for $1.7 million in April to install new filtration technology. Employees from the firm collected water samples from the pool on Tuesday. The algae issue has persisted for decades, particularly in warm summer months, with previous attempts at renovation—including a $35 million effort under President Barack Obama in 2012—failing to fully resolve the problem. The pool’s shallow design and proximity to the Tidal Basin contribute to algae proliferation. A local resident, Redmond Walsh, documented the green water on social media, drawing widespread attention to the issue.