Algae returns to Lincoln Memorial Reflecting Pool after $14.2 million repair

Green water returned to the Lincoln Memorial Reflecting Pool just after a $14.2 million repair project ended, turning one of Washington’s most visible landmarks into a case study in maintenance, climate stress, and federal stewardship. The shallow basin between the Lincoln Memorial and the Washington Monument has long been a national stage. Now it is again drawing attention for the wrong reason.

Federal contracting records showed that the overhaul included $1.7 million for an ozone nanobubbling system and $14.2 million for Atlantic Industrial Coatings to line the basin in “American Flag Blue.” The work began in April and finished last week after about eight weeks of construction, during which supply lines sat dormant. Interior Department officials said the green material now appearing in the pool was residual algae from those dormant lines and part of a normal startup process.

The National Park Service has been using nanobubble technology and cleanup crews to clear the water. Visitors who saw the pool green instead of blue said the scene undercut the point of the expensive repair, with one calling it “money down the drain.” Another said he came expecting the promised blue water and saw green instead.

The episode lands on a site that carries unusual symbolic weight. The Reflecting Pool was begun as part of the Lincoln Memorial landscape, was not finished in time for the memorial’s dedication on May 30, 1922, and was completed two years later. Since then, it has served as the backdrop for Marian Anderson’s 1939 concert, Martin Luther King Jr.’s 1963 “I Have a Dream” speech, John F. Kennedy’s memorial service, and an anti-Vietnam War rally in 1967. It remains one of the most recognizable and filmed places in the capital, stretching along the National Mall from Abraham Lincoln’s memorial to the Washington Monument.

This was not the first time a major renovation was followed quickly by algae. After the 2012 Obama-era $34 million restoration, the National Park Service installed ozone filtration, but algae still appeared within weeks. Officials later drained the pool again and doubled the ozone level.

Environmental conditions make the problem predictable. The U.S. Environmental Protection Agency says excess nitrogen and phosphorus contribute to algae blooms, and warm temperatures, sunlight, stagnant water, and shallow outdoor basins can intensify them. With the nation’s 250th anniversary approaching, the Reflecting Pool is once again testing whether federal agencies can preserve a landmark without repeatedly paying to fix the same failure.