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Less than two weeks after a $14 million renovation of the Lincoln Memorial Reflecting Pool wrapped up, the water turned green. Workers with skimmers and chemicals scrambled to contain an algae bloom spreading across one of the most photographed landmarks in Washington, D.C. — exactly the kind of embarrassment the project was supposed to prevent. The timing could not be worse: the U.S. is weeks away from its 250th anniversary celebrations centered on the National Mall.
President Donald Trump ordered the renovation to transform the pool into what he called “American flag blue,” painting its basin a darker shade and installing ozone nanobubbler technology to keep the water clear. On June 3, Trump declared the project complete on Truth Social, writing that it would be “the first time since the day it was built, 1922, that it has worked, and worked wonderfully, indeed!” Within days, a thick algae bloom contradicted that claim entirely.
The pool holds roughly 6.5 million gallons of water across a surface larger than six soccer fields. It is shallow, sun-exposed, and fed by untreated water drawn from a nearby basin already prone to algae. Cochise Wanzer II, president of Pool Service Company in Arlington, Virginia, put it plainly to the Associated Press: “You’re basically taking natural, untreated river water, pumping it in and expecting it to do something different from what it would do out in the open.”
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The Dark Blue Paint Experts Warned About Is Now a Suspect in the Bloom
Before a single gallon of water went back into the pool, aquatics professionals flagged the renovation’s central flaw. Tim Auerhahn, chairman of The Aquatic Council, told The New York Times directly: “Painting is not going to solve that problem.” The renovation did not include an overhaul of the pool’s pipes or its water treatment system — the infrastructure at the root of its chronic algae and clarity issues going back decades.
The darker coating may have actively worsened conditions. Steve Goodale, owner of Swimming Pool Steve pool service, explained the mechanism clearly: when a body of water is changed from a light surface to a dark one, it absorbs more heat. Alla Silkina, an algal biotechnology expert at Swansea University, confirmed the dynamic, telling Newsweek that darker surfaces absorb more solar radiation, increasing local water temperatures and creating conditions more favorable to algal growth.
The paint itself may carry another risk. Sarah Goodrich, an adjunct professor of geography at the University of Cincinnati, noted that certain paints contain nitrogen and phosphorus — both nutrients that feed algae. Whether the specific coating used in the pool contains these compounds remains unclear, but if it does, the renovation’s surface treatment could be directly fueling the bloom it was meant to eliminate. Goodale described the situation bluntly: “They’re kind of fighting an uphill battle here.”
Workers Poured Hydrogen Peroxide Into a 6.5-Million-Gallon Pool. Experts Say It Won’t Be Enough
By mid-June, National Park Service crews were deploying a mix of interventions: swimming pool vacuums, ozone nanobubbler systems, and hydrogen peroxide poured directly into the water. The nanobubblers work by aerating the water with oxygen, mimicking the natural cleaning effect of a waterfall — sound science, according to Goodale. But the open-air environment means the pool is continuously exposed to pollen, bird waste, and other nutrient sources that feed algae regardless of treatment.
The hydrogen peroxide presents its own limits. Hans W. Paerl, a research professor of marine and environmental sciences at the University of North Carolina at Chapel Hill, said the treatment “may work, but it’s really only a temporary fix, because the hydrogen peroxide is active for only a few weeks or so.” The chemical dissipates quickly, turning into water, which means repeated and costly applications are required. Paerl added that workers would likely need a tanker truck’s worth of the chemical to have any meaningful effect on a pool this size.
Brooks Barrett, who studies marine plant life at the Smithsonian Institution, offered perhaps the sharpest assessment of the pool’s fundamental problem. “The reflecting pool is perfect for algae,” Barrett told Politico. “If you were trying to biofarm algae, this would be the way to go. It’s warm, it’s stagnant, it’s perfect.” Auerhahn echoed the structural diagnosis: fixing algae in a pool this complex requires addressing circulation, filtration, chemistry, waterproofing, and structural integrity all at once — not one element in isolation.
The Bloom Has a Political Deadline. The Science Does Not
The White House tied this project directly to the Fourth of July celebrations marking the country’s 250th anniversary. Interior Secretary Doug Burgum has joked publicly that he’s become Trump’s “pool guy.” But the algae operates outside political timelines. Paerl noted that temperature drops are typically what dissipate blooms naturally, and Washington’s summer heat is at its peak right now. The window for clearing the pool before the anniversary is narrow and closing.
This is not a new failure. The 2012 renovation of the same pool — a $34 million project under President Obama — produced an algae bloom within weeks of reopening, prompting crews to drain and clean it all over again. Auerhahn recalled the pattern plainly: “Right away, when they reopened it in 2012, just a couple weeks later, the algae was back.” The current crisis follows the same arc, suggesting the underlying problem was never solved by either administration.
Climate change ensures the problem will only compound over time. Paerl warned that algae blooms are expanding into latitudes that once saw none, as warming temperatures extend the growing season earlier into spring and deeper into fall. “The window of opportunity for these blooms is expanding because of climate warming,” he said. A $14 million renovation built around aesthetics, applied to a pool that has defeated every major overhaul since 1922, now sits green in the June heat — a few weeks before the cameras arrive.