WASHINGTON — Federal officials are deploying specialized treatments including hydrogen peroxide and nanobubble technology to combat an algae bloom in the Lincoln Memorial Reflecting Pool on the National Mall, days after the completion of a multimillion-dollar renovation, the Interior Department said.
The shallow reflecting pool was refilled in early June following more than $14 million in work that included painting the basin “American flag blue,” officials reported. Green algae became visible soon after, prompting cleanup efforts by National Park Service crews.
Interior Department spokespeople attributed the bloom to residual algae from supply lines that sat dormant for weeks during construction, describing it as part of the normal startup process for the pool. Crews have used hydrogen peroxide — described as a milder treatment than chlorine — and high-tech nanobubble ozone systems to neutralize the algae, with workers vacuuming dead material from the bottom.
“Due to deploying the advanced nanobubbler technology, the algae is dead and being vacuumed up as we speak,” a department spokesperson told reporters. Officials maintained that the water would be restored to clarity ahead of upcoming July 4 events.
The renovation, advanced ahead of the U.S. 250th anniversary celebrations, also involved sealing and other repairs to address longstanding issues including leaks. However, satellite imagery analysis indicated the recent algae levels were among the highest recorded for June in recent years, according to reports.
Some observers noted additional problems, including uneven paint application and sections of the new coating appearing to peel, though federal officials have not issued detailed statements confirming the extent of those issues.
The Lincoln Memorial Reflecting Pool, a century-old landmark, has faced recurring algae challenges due to its shallow depth, warm water and other environmental factors, officials and experts have said. Previous renovations, including one during the Obama administration, encountered similar issues.
As of Saturday, National Park Service crews continued maintenance operations at the site. The pool remained open to visitors, though with visible green tint in parts of the water during the ongoing treatment. No timeline for full resolution was provided, and investigations into the precise causes continue.
Tourism officials noted that the broader National Mall area was operating normally.
