WASHINGTON — The Lincoln Memorial reflecting pool is once again making headlines, this week for turning green.
The Washington, D.C. landmark was refilled with water earlier this month after President Trump had its neutral grey bottom repainted “American flag blue.” The multi-million dollar project produced subtle results in the eyes of many observers, even as Trump and Secretary of the Interior Doug Burgum — whose agency managed the renovation — touted its success.
In recent days, however, the pool has taken on a verdant hue — the result of algae blooms that experts say are to be expected in these conditions.
“It’s called ‘New Pond Syndrome,'” says Steve Goodale, a Canadian swimming pool specialist known online as “Swimming Pool Steve.” “It’s a known thing that happens when you take a natural, clear body of water like this that sits in an open air environment and you try to start it up, very often you end up with green water almost immediately.”
Goodale says the process took longer — a matter of days — to unfold in this case likely due to the sheer size of the pool, which measures 2,030 feet long and has a surface area of approximately 338,000 square feet.
“Excellent conditions” for algae growth
Rosalina Stancheva Christova, a professor of aquatic ecology at George Mason University in Virginia, took water samples from the pool on Tuesday. She confirmed the algae belongs to the genus Desmodesmus, which she said is “growing in excessive amounts” but is not toxic or harmful.
Christova says this kind of common green algae is found all over the region, especially this time of year. The reflecting pool in particular provides “excellent conditions” for algae growth, she said: shallow, stagnant water, strong sunlight and no shade.
“It could happen every single summer,” she added. “But it seems that the disturbance of the pond during the renovations [is] accelerating this process.”
Christova said last month’s renovations may have affected the balance of nutrients in the pool, potentially accelerating the algae blooms. Goodale similarly views the resurfacing as one of several contributing factors.
“The new, darker interior surface is going to absorb more sunlight,” Goodale says. “It is going to result in water that’s warmer, and that ultimately is going to lead to more prolific algae growth.”
The Trump administration has said the algae came from residual material in supply lines that had lain dormant for weeks. Their growth was likely exacerbated by the extreme temperatures that hit D.C. last week, bringing heat index values to 95 degrees and above.
Algae has resurfaced in the reflecting pool periodically over the years — including immediately after it reopened from its last major renovation in 2012, forcing the National Park Service to drain it, refill it and recalibrate its ozone level. And in 2019, crews had to drain four million gallons from the pool to fix a broken water line that had algae growing in it.
An Interior Department spokesperson told NPR over email that algae and other contaminants have “long plagued the Reflecting Pool since 1922,” pointing to the Obama-era renovation as an example.
“Unlike under Obama and Biden, the National Park Service is actually maintaining the beautifully completed Reflecting Pool,” they added.
Responding with tiny bubbles and big vacuums
The Trump administration is using a mix of mitigation strategies, including pouring hydrogen peroxide into the water to kill the algae.
The Interior Department says hydrogen peroxide is a “milder treatment than chlorine and is used in spas and specialty pools like natural swimming pools,” adding “there are no harmful side effects to marine life or to the environment.”
Workers are also deploying what the department calls “high-tech nanobubble ozone technology” to neutralize algae and other pathogens in the pool. The department says that approach is validated by several universities and the National Oceanic & Atmospheric Administration.
Those ozone bubbles are so tiny the human eye can’t even see them, Goodale says.
“The best way to describe it is that the bubbles are neutrally buoyant, so they won’t just rise to the surface and disappear readily,” he explains. “They can last for weeks, if not months in the water, doing their oxidizing thing and keeping the algae at bay.”
‘A monumental effort’
Goodale says it’s more complicated than treating the average backyard swimming pool, since the reflecting pool — despite its name — is actually more akin to a “manmade shallow lake.” He says it’s hard to predict just how long it will take to completely solve the algae problem, calling it “a monumental effort, literally.”
The Interior Department posted on X Wednesday that the nanobubble technology had “very effectively killed the algae,” and National Park Service crews would spend several days vacuuming up the dead algae from the bottom of the pool.
But as of Thursday morning, much of the pool — especially in the center — was still bright green.
Work continued on both ends of the pool. Nanobubble machines deposited their tubes into the water, as mobile vacuuming systems known as “trash pumps” hummed loudly from the shore. Handfuls of workers stood either in the pool or on the edge maneuvering long-handled vacuums back and forth. Their contents, including pistachio-colored water, poured out of hoses laying in the nearby grass.
The work zones were marked off by orange cones, but passersby walking the length of the pool appeared relatively unfazed. Some stopped to peer down and snap pictures of the water itself — including sections of paint that had visibly peeled off — while others were more focused on getting a photo of the Washington Monument in the background.
Loay Hidmi was walking deliberately along the edge of the pool closest to the Lincoln Memorial, hands clasped behind his back, looking over the ledge. The relatively new D.C. resident is a civil engineer who specializes in water treatment, and has been coming by the pool all week to see the progress for himself. He estimates it’s about 80% of the way there.
“I’m taking pictures of it … for the last week and I can see the gradual change,” he said. “So I’m hopeful. But we’ll have to see if it gets sustained.”
What happens next?
Hidmi worries that the algae could come back, given the favorable conditions posed by the sunny, shallow pool.
He acknowledges that’s mostly an aesthetic concern, given how much the administration has just spent on repainting the pool, but says it also raises questions about their process.
“In water systems, when you fix something, you need to look at the step before it and the step after,” he said.
Goodale agrees. He says that when a water system is taken offline, the pipes still remain full of water — “they don’t just gravity-drain away” — and need to be flushed out before any refilling. And he says eliminating algae is no substitute for dealing with underlying filtration issues.
“That’s like the equivalent of mowing the lawn when perhaps it needs to be something else that addresses the source nitrates and phosphorus, so that it’s more like pulling the weeds out by the root,” he says.
In the meantime, Christova, the algae expert, would like to see the water monitored weekly.
“If we don’t have any control over algal growth, we don’t know what is growing,” she said, adding that not all types of algae are as harmless as the one currently blooming in the pool.
When asked about plans for maintenance and algae prevention, White House spokesperson Taylor Rogers told NPR: “Thanks to President Trump, new lining and industrial grade materials will permanently seal the Reflecting Pool, which previously leaked 16 million gallons per year and wasted countless taxpayer dollars.”
Even after the Obama-era renovation, the reflecting pool suffered from broken pipes and water leaks requiring costly refills, according to a Department of the Interior report from fiscal year 2023. It called for new expansion joints, supply and return lines with thicker walls, saying “an improved distribution system will ensure the water can be circulated through the treatment plant, filtered, and treated with ozone.”
This latest renovation does not appear to have addressed the pipe problems, even though it did involve replacing failing expansion joints, resealing the pool, removing truckloads of garbage and “fixing the water system, drainage and so much more,” as Trump wrote on Truth Social in May.
Along the way, the cost of the project grew from Trump’s initial $2 million price tag to at least $14 million. Federal contract records show the government is paying $1.7 million to an Ohio-based company for the nanobubble technology alone.
“The scope of the Project has been greatly enlarged as we became involved because we realized how important it would be to Washington, D.C., and the record number of visitors coming to our now very safe Capital for all of the upcoming events in celebration of our 250th Anniversary,” Trump wrote.

Federal immigration officers often use facial recognition technology to identify immigrants in the field. Now, a newly revealed document from the Department of Homeland Security outlines plans to give local police working on its behalf the same type of technology.
The document, first reported earlier this month by the tech news outlet 404 media, is a Privacy Threshold Analysis, which is essentially a federal report assessing whether the privacy implications of a tool warrant further government study.
The tool in question is a mobile app called the ICE Task Force Module, which allows local police to scan the faces of people they stop in their communities.
The app then compares the facial scan against more than 250 million government records. Those include the State Department’s Visa records and records from the Traveler Verification Service, used by the Transportation Security Administration at airports to verify identities on international flights.
Once police scan a person’s face, the app then instructs an officer either to “not detain or arrest,” or it gives the officer a reference code to use to obtain more information from ICE.
The photos captured by the app are then stored in an internal DHS system for 15 years, the document states.
DHS declined to provide NPR with more insight about the app and how it is used. In a statement, the agency said ICE is committed to ensuring that the local police who partner with them have the tools needed to support ICE’s mass deportation mission.
Those local officers, called “ICE non-federal law enforcement officers” in the document, are likely participants in the federal 287(g) program. A subset of that program, the Task Force Model, gives local police the authority to arrest immigrants on ICE’s behalf during their routine police duties. There are around 1,300 police agencies participating in the Task Force Model nationwide.
The DHS analysis “raises more questions than I think it answers,” says Clare Garvie, deputy director of the Technology Law and Policy Program at New York University School of Law’s Policing Project.
For one, the document says the app launched last September, which suggests police are already using it.
It also seems to work similarly to Mobile Fortify, a facial recognition app that ICE and officers with Customs and Border Protection already use, but it’s unclear if the new app uses the same technology or something entirely its own.
Garvie says there are also questions about how and when police will deploy the app.
“It’s unclear to me whether a pre-existing stop based on some level of suspicion is required before law enforcement can use this app,” Garvie says. “Can they walk around taking photos of whoever as sort of a dragnet way to attempt to identify individuals who might be in the country unlawfully?”
That sort of surveillance already appears to be happening at the federal level: In places like Minnesota and Maine, community members observing ICE activity reported that federal immigration officers would take photos of their faces and license plates. They said the officers would often know personal information about them, including their names and where they live.
Privacy experts told NPR that allowing local police to conduct similar surveillance could create a chilling effect on freedom of speech, if people begin to worry they’ll face repercussions for attending protests, for instance, or for legally observing ICE activity in their communities.
Homeland Security Secretary Markwayne Mullin acknowledged at a congressional hearing this month that the agency has used facial recognition technology on protesters, and had been able to identify people who were present at protests in Oregon that were also at the recent protests outside the Delaney Hall Detention Facility in Newark, N.J.
What’s more, Garvie says, facial recognition technology is not always accurate, and there have been cases of people detained by ICE who were wrongly identified by the technology.
Patrick Eddington, a senior fellow in homeland security and civil liberties at the Cato Institute, a libertarian think tank, says giving police this capability magnifies its potential problems.
“This kind of technology which can impact individual rights, when it’s scaled, it can have potentially very, very large effects affecting lots and lots of people,” he says. “It’s like a Bill of Rights disaster pretty much waiting to happen.”
In its statement to NPR, DHS said its law enforcement methods are constitutional.
“Like other law enforcement agencies, ICE employs various forms of technology to investigate criminal activity and support law enforcement efforts while respecting civil liberties and privacy interests,” the statement said.
But Eddington says U.S. citizens will get caught up in this surveillance. Officers conducting immigration enforcement, whether they are federal or local, will not know a person’s citizenship status before they conduct a scan.
“It is conceivable that a photo taken by an ICE non-federal law enforcement officer using the TFM mobile application could be that of someone other than a removable individual, including U.S. citizens,” the DHS document states.
Because every photo taken through the app is kept for 15 years, Eddington says that suggests a long-term government record of citizens and immigrants alike.
The administration has repeatedly denied the existence of a database of protesters, despite instances in which federal agents have told community members observing them that their photo will end up in a database of “domestic terrorists.”
However, earlier this month, NPR reported on a previously unpublished letter sent to members of Congress in which former acting ICE director Todd Lyons indicates the agency gives itself wide latitude to collect information on the people its officers encounter.
“This app wouldn’t work if they didn’t have databases to pull people’s pictures from and compare against,” says Cooper Quintin, a senior staff technologist with the Electronic Frontier Foundation, a nonprofit that advocates for digital privacy. “They’re playing semantics. They’re certainly not being forthright. You know, do they have a database of protesters? Maybe they don’t call it that.”
He says allowing police to use this technology to do immigration enforcement is a significant expansion of ICE’s operations.

The bottom of the pool was painted at the direction of President Donald Trump and refilled with water about two weeks ago. Since then, algae that blooms in the Reflecting Pool every summer returned, making the pool green.
Crews have been scrubbing the algae out and using nanobubble ozone technology to try and clean the pool. Workers were recently seen dumping hydrogen peroxide in the water.
Thursday, some of the blue paint started lifting from the bottom. About half-way down the south side of the Reflecting Pool, a 2- to 3-foot section appeared to be peeling away near the pool’s edge. As the wind blew, the chunk rose above the water, ripping away from the bottom just a little bit more.
Derek Amspaugh visiting D.C. from Columbus, Ohio, stopped to take a look.
“It’s definitely concerning, yeah; you’re spending $11 million, you’d like to see quality work being done.”
The Trump administration has said the cost of the renovation is around $14 million.
John Ritter, who lives in Northern Virginia, suggested the issue could be emblematic of the Trump administration.
“It’s a bit of a metaphor, I think, for some of the other projects they are trying to do.”
It’s unclear whether the hydrogen peroxide, the scrubbing of the algae or the nanobubble technology being used has anything to do with the peeling.
As of Thursday afternoon, about a third of the pool looked clean and blue — the rest was the algae green color usually seen in the summer.
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US federal government workers continue to take on the green hue that has swept across Washington’s reflecting pool, an increasingly fiendish battle the Trump administration compared to its war with Iran.
After Donald Trump ordered a $14.2m refurbishment to turn the monument “American Flag blue” in time for the country’s 250th birthday celebrations, the administration encountered a formidable foe: algae.
For days, the pool has been fluctuating between various shades of green, frustrating efforts to ensure it adopts the US president’s preferred color. And by Thursday parts of the coating laid by Atlantic Industrial Coatings in an effort to turn the monument “American flag” blue had appeared to start peeling off.
Workers were seen on site in waders, attempting to fish out algae and eliminate patches of deep green across the pool.
Hours earlier, the US Department of the Interior – which oversees the National Park Service – had claimed the water was “crystal clear”, and blamed the “Fake News Media” for reports to the contrary.
In a statement on X, after eyewitnesses saw the pool looking distinctly murky, the department went so far as to liken the administration’s purported victory against algae to its purported victory against Iran.
“The Reflecting Pool water is crystal clear, and our National Park Service team is now vacuuming up the dead algae resting on the bottom of some parts of the Reflecting Pool – just like the destroyed Iranian Navy resting on the bottom of the Persian Gulf,” the department’s press office said.
Both campaigns have so far failed to match Trump’s stated intentions. At the outset of the US-Israel war on Iran, he vowed to eliminate Iran’s nuclear program and destroy its ballistic missile program.
A peace deal signed on Wednesday left the US president with Iran’s word not to build a bomb and no mention in writing of the ballistic missile program.
The reflecting pool – one of Washington DC’s most historically symbolic attractions, and the scene of Martin Luther King’s 1963 “I have a dream” speech – has been one element of Trump’s efforts to recondition Washington during his second term.
A no-bid contract to waterproof and repaint the site, which dates back over a century, raised eyebrows. It was awarded to a Virginia-based company, Atlantic Industrial Coatings, which had previously carried out work on a swimming pool at one of the president’s golf clubs.
The administration had initially claimed that “residual” algae would be cleared in the immediate aftermath of the renovation. But it has proliferated amid warm weather.
It later suggested the installation of a water treatment system, described as “nanobubbler technology”, would help address the issue. The technology had “very effectively killed the algae”, the interior department claimed.

Accenture CEO Julie Sweet is telling onlookers to hold their judgment.
Shares at the global professional services firm fell nearly 20% on Thursday and have dropped about 50% since this time last year.
In its third-quarter earnings call on Thursday, it reported a 2% drop in new bookings compared to the third quarter of 2026. It also reported revenues of $18.7 billion, up $1.0 billion from the same quarter in 2025, though that was below expectations.
Sweet’s message to the investors betting on the company was simple: Be patient. As companies seek Accenture’s help to integrate AI, she said, the numbers will improve.
“The investors, I think, are missing the AI tailwind and how we’re positioning ourselves for the long-term,” Sweet said on CNBC on Thursday after the earnings call. She pointed to an increase in consulting sales and to the $9 billion in managed services it brought in. “AI scaling will take some time,” she said.
On Thursday’s earnings call, Sweet also highlighted the number of clients moving beyond AI pilots into production. In this area, she said the firm continues to see promise as demand for large-scale AI transformation grows.
“We’re doing more consulting now because clients are doing more reinvention,” she said, using the company’s in-house term for AI transformation. “It really depends on how fast enterprises are ready to scale. There’s a lot of work to do to scale. We are optimistic because we see what our clients are asking us to do.”
Last year, Accenture made a massive pivot in the AI race as it consolidated its strategy, consulting, song, technology, and operations services into a single unit known as “reinvention services.”
“What we’re going to do now is make it even easier to bring those solutions, embed data and AI, so we can really scale across our client base and into new markets using our reinvention services,” Sweet told CNBC last year.
Investors, however, appear to be running out of patience.