WASHINGTON — Green algae has spread across portions of the Lincoln Memorial Reflecting Pool in Washington just days after the landmark reopened following a multimillion-dollar renovation, prompting federal crews to deploy treatment measures as officials work to restore the pool’s appearance.
National Park Service workers were seen this week applying hydrogen peroxide and operating a recently installed nanobubble ozone system to address the algae bloom, according to the Department of the Interior and eyewitness accounts reported by Reuters and other news organizations. The nearly century-old reflecting pool, which stretches between the Lincoln Memorial and the Washington Monument, had been drained, cleaned and refilled as part of renovation work completed earlier this month.
The renovation was undertaken ahead of events marking the 250th anniversary of U.S. independence in 2026. President Donald Trump had promoted the project as part of a broader effort to improve prominent landmarks in the nation’s capital. Reports said the work included resurfacing and repainting the pool and installing new equipment intended to help control algae growth.
Algae became visible shortly after the pool was refilled, according to media reports and photographs from the site. An Interior Department spokesperson said the growth was “residual” algae linked to supply lines that had remained dormant during weeks of construction and described it as part of the startup process following the renovation.
“The current algae is residual from supply lines that sat dormant for weeks,” an Interior Department spokesperson said, according to multiple reports. Officials said treatment measures already in place are expected to address the problem.
Scientists and water-quality experts interviewed by news organizations said algae has long been a recurring challenge at the reflecting pool. They noted that warm temperatures, sunlight and nutrient-rich water can contribute to blooms, while treatment methods such as hydrogen peroxide may help control growth in the short term.
The reflecting pool has experienced algae problems in previous years, including after earlier renovation efforts, according to reports. Officials have said the newly installed filtration and nanobubble systems are intended to improve long-term water quality management.
As of Tuesday, workers continued treating affected sections of the pool, while patches of algae remained visible in some areas. Federal officials said cleanup operations and monitoring efforts were ongoing.
