Worker in waders standing waist-deep in a green algae-filled reflecting pool, holding a long pole, with park visitors and equipment visible on the shore behind them.
The Mega Agency
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Why Did Park Service Workers Pour Jugs of Hydrogen Peroxide into the Lincoln Memorial Reflecting Pool?

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The Lincoln Memorial Reflecting Pool had just been drained, resurfaced, and repainted “American Flag Blue” as part of a roughly $14.2 million renovation. Within a week of refilling, the algae came back and turned it green.

So workers in waders started pouring gallon jugs of 12% hydrogen peroxide directly into the pool, along with a nanobubble ozone treatment. Videos of the labeled jugs going in surfaced around June 16, 2026 and spread fast online, with late-night hosts already riffing on “puke green” versus “American Flag Blue.”

A section of the Lincoln Memorial Reflecting Pool liner peeled up while crews work to clear algae from the water
A peeled section of the new pool liner is visible as workers tackle an algae outbreak at Washington, D.C.’s Lincoln Memorial Reflecting Pool on June 19, 2026. Photo by MEGA.

The Interior Department and National Park Service confirmed the chemical, calling it a milder option than chlorine that’s common in spas and natural swimming pools, with no harmful effects on wildlife or the environment. Ducks and ducklings have kept paddling through the green water while crews work around them.

The pool has fought algae since it opened in the 1920s, and it bloomed again quickly after the last big renovation in 2012. Officials are partly blaming “residual algae” that sat in the supply lines during construction and came roaring back once the water was warm. Experts also point to the new darker blue bottom, which absorbs more heat than the old lighter surface and pushes temperatures up in a pool that’s already shallow with limited circulation.

A section of the Lincoln Memorial Reflecting Pool liner peeled up near crews working to remove algae from the water
A peeled section of the newly installed liner is visible as workers tackle an algae outbreak at the Lincoln Memorial Reflecting Pool in Washington, D.C. on June 19, 2026. Photo by MEGA.

The newer wrinkle is the paint itself. Large sheets of the fresh blue coating have started peeling off and floating on the surface, creating blue islands in the green water. Some observers have wondered whether the hydrogen peroxide, an oxidizer, affected the new sealant, though the contractor has said any issues will be handled through normal maintenance and officials haven’t tied the peeling to the chemical.

National Park Service crew members working to remove algae from the Lincoln Memorial Reflecting Pool on the National Mall in Washington, D.C.
National Park Service workers clear residual algae from the Lincoln Memorial Reflecting Pool on the National Mall in Washington, D.C., on June 17, 2026, following a bloom tied to the restart of pool operations after renovations. Photo by MEGA.

The open question now is whether the pool will be back to blue in time for July 4th and the America 250 celebrations.

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Worker in waders standing waist-deep in a green algae-filled reflecting pool, holding a long pole, with park visitors and equipment visible on the shore behind them.
The Mega Agency
A section of the Lincoln Memorial Reflecting Pool liner peeled up while crews work to clear algae from the water
A peeled section of the new pool liner is visible as workers tackle an algae outbreak at Washington, D.C.'s Lincoln Memorial Reflecting Pool on June 19, 2026. Photo by MEGA.
A section of the Lincoln Memorial Reflecting Pool liner peeled up near crews working to remove algae from the water
A peeled section of the newly installed liner is visible as workers tackle an algae outbreak at the Lincoln Memorial Reflecting Pool in Washington, D.C. on June 19, 2026. Photo by MEGA.
National Park Service crew members working to remove algae from the Lincoln Memorial Reflecting Pool on the National Mall in Washington, D.C.
National Park Service workers clear residual algae from the Lincoln Memorial Reflecting Pool on the National Mall in Washington, D.C., on June 17, 2026, following a bloom tied to the restart of pool operations after renovations. Photo by MEGA.