Reflecting Pool algae returns in Washington, DC, prompting cleanup push

Algae has turned the Lincoln Memorial Reflecting Pool green again, turning one of Washington’s most photographed landmarks into a visible reminder of how fragile the capital’s showcase spaces can be. The bloom came back after a renovation billed at roughly $14 million to $14.8 million, just as the pool was meant to help stage the run-up to America’s 250th anniversary and Independence Day.

The problem is not only cosmetic. The Reflecting Pool was completed in 1924, two years after the Lincoln Memorial was dedicated, and it received a reinforced concrete slab foundation in 1929 after soil settlement problems. The landscape itself traces back to the 1901-1902 McMillan Plan and the work of Henry Bacon and Frederick Law Olmsted Jr., a design legacy that makes the pool one of the most recognizable and filmed sites in Washington. It is also fed by water pumped from the Tidal Basin, a setup that helps explain why algae and water-quality problems can return.

The National Park Service closed the pool and nearby areas on April 10 for work that was scheduled to run through June 10 at 7:00 p.m. The project called for cleaning the pool, repairing joints and installing lining material. The basin was reported to hold about 6.5 million gallons of water across more than 300,000 square feet, a scale that makes any maintenance failure immediately visible to the public.

Federal officials responded with hydrogen peroxide and nanobubble ozone technology. The Interior Department said the nanobubbles are intended to kill algae, pathogens such as E. coli and other contaminants that have long affected the pool. Workers were also seen vacuuming algae from the bottom. Politico reported that Green Water Solutions was paid $1.7 million to install an ozone nanobubbling system, while Pearl Purity Water Solutions has treated the pool since 2021.

The White House has folded the cleanup into a broader beautification push tied to America’s 250th anniversary. Its Freedom 250 campaign says July 4, 2026 marks 250 years of American independence, and the administration posted a video in May titled Restoring the Reflecting Pool. But the rapid return of green water has undercut the optics of that effort, especially since the basin was described as American flag blue before the bloom made it chartreuse again.

A USA Today expert said the green tint could linger for months, possibly until October. That makes the Reflecting Pool less a one-off nuisance than a case study in deferred maintenance, heat and water-quality stress, and the limits of federal management at one of the nation’s most symbolic public spaces.