Interior says workers used hydrogen peroxide in Lincoln Memorial Reflecting Pool to reduce algae growth

Workers have been observed adding hydrogen peroxide to the Lincoln Memorial Reflecting Pool as part of an effort by the National Park Service to reduce algae growth, a Department of the Interior spokesperson said, according to The Hill on June 16, 2026.

The Department’s explanation tied the algae control step to ongoing maintenance of the iconic water feature on the National Mall. The reflecting pool project is under the National Park Service’s jurisdiction within the National Mall and Memorial Parks unit.

The spokesperson said the approach involves deploying hydrogen peroxide in the pool, rather than mechanical removal alone, to combat algae accumulation. The report did not provide additional technical details about the concentration, application schedule, or whether the chemical treatment is part of a longer-term maintenance plan.

The algae-control effort comes after the Trump administration’s $13.1 million renovation of the Lincoln Memorial Reflecting Pool, an expense that drew public attention and criticism. The renovation work, as described in The Hill report, included repainting the base of the pool and other updates intended to refresh the water feature.

In its June 16 reporting, The Hill linked the new chemical treatment to the aftermath of that renovation, describing it as a response to algae growth that has persisted in the pool. The report characterized the hydrogen peroxide step as part of an operational response by the Interior Department and the National Park Service, not as a separate construction project.

Public maintenance of federal historic and memorial sites can involve competing priorities, including preservation standards, visitor safety, and environmental handling of materials used for treatment. In this case, the Department’s stated use of hydrogen peroxide raises questions about how chemical treatments are monitored, how runoff and disposal are handled, and how maintenance decisions are documented.

For visitors and nearby memorial events, algae growth in reflecting pools can affect aesthetics and potentially water conditions. The Department’s next steps were not detailed in the June 16 report, including whether additional treatments are planned or whether testing will be used to measure the chemical’s effectiveness over time.