Algae turns renovated Lincoln Memorial pool green again

The Lincoln Memorial Reflecting Pool has turned green with algae just days after the Trump administration completed a multimillion-dollar renovation intended to make the National Mall landmark “American flag blue” for the nation’s 250th anniversary celebrations.

The change in color came after hot weather in Washington, D.C., and followed repeated public praise from President Donald Trump, who had touted the work as part of a broader effort to beautify the capital before July 4. Last month, while the pool was still under construction, Trump drove past it and praised the new blue surface.

“It never had the color people wanted, but now it’s going to have the great color,” he said at the time.

In a Truth Social post days before the water turned green, Trump said the pool’s surface was now a “very complex, but powerful, Dark Blue.” He later told reporters in the Oval Office that “everybody’s looking at that Reflecting Pool” and said the project cost around $10 million. “They can’t believe it reflects. We used a dark blue, it’s called American flag blue,” he said.

The Guardian reported the project cost $14.2 million. NBC News reported that The New York Times said the government is paying more than $13 million through a no-bid contract to a company that previously performed work at Trump National Golf Club in Sterling, Virginia. The Guardian identified the company as Virginia-based Atlantic Industrial Coatings and said it had worked on a swimming pool at one of Trump’s golf clubs.

Interior Secretary Doug Burgum, asked at a congressional hearing about reports on the contract, said he was “positive that we followed all of the required bidding rules.”

The Department of the Interior said the National Park Service is working to treat the algae. A spokesperson told NBC News the agency was using “high-tech nanobubble ozone technology” to kill algae, pathogens and contaminants, along with hydrogen peroxide, which the spokesperson described as milder than chlorine and used in spas and natural swimming pools.

“There are no harmful side effects to marine life or to the environment,” the spokesperson said.

A department spokesperson told The Guardian that “nanobubbler technology” was being used and said Tuesday, “The nanobubbler technology has successfully destroyed the algae bloom that has plagued every pool reopening since 1922.” The spokesperson added: “Now, due to deploying the advanced nanobubbler technology, the algae is dead and being vacuumed up as we speak. We thank President Trump for fixing the reflecting pool for good.”

National Park Service employees were seen Monday using skimmers to remove algae from the pool, The Guardian reported. Despite the visible discoloration, the White House posted an image Monday showing the pool blue and said, “Making D.C. safe and beautiful again one cleanup at a time.” NBC News reported that the water was green at the time of the post.

Shallow artificial bodies of water such as the Reflecting Pool are susceptible to algal growth because they are warm, sun-exposed and can contain nutrients. The Centers for Disease Control and Prevention says nitrogen and phosphorus can fuel algal blooms. Those nutrients can come from animal waste, including geese and ducks near the pool, and from fertilizer carried by runoff after rainstorms.

The repainting drew legal opposition before the algae appeared. The Cultural Landscape Foundation sued the administration in May to try to stop the work. “The dark grey, achromatic basin was not incidental to the design. It was the design,” attorney Alexander Kristofcak wrote for the plaintiffs.

The pool project is one of several Washington changes Trump has promoted, including work on fountains, a new surface at the World War II Memorial fountain, a planned 250-foot arch near the Potomac River and a White House ballroom project that included demolition of the East Wing. Those projects have also drawn criticism and legal challenges from critics, preservationists, veterans and historians.