Late-Night Hosts Mock $14.2 Million Reflecting Pool Project as Algae Turns Water Green

Q: Why did a $14 million renovation turn the Lincoln Memorial's reflecting pool green just days after completion?

The pool turned green because it developed a fast algae bloom soon after being refilled, and the renovation likely created conditions that made that easier. Experts say the new dark blue waterproof coating on the pool floor probably absorbed and held more heat than the previous surface. Warmer water helps algae grow faster, especially in a large, shallow outdoor basin exposed to summer sun. Independent reporting also pointed to high phosphate levels, which can feed algae, and to the reflecting pool’s long history of circulation and algae problems despite earlier repairs. Federal officials offered a narrower explanation, saying the discoloration came from “residual” algae left in supply lines and pumps during startup. Once the pool was refilled, that algae could quickly spread through millions of gallons of water. Crews were then seen skimming the surface and adding hydrogen peroxide, while a nanobubbler ozone treatment system was used to clear the water. So the $14 million renovation did not itself “paint” the pool green; it was followed almost immediately by an algae outbreak. The most likely reasons are a combination of residual algae in the system, warm weather, nutrient-rich water, and a darker new lining that may have raised water temperature enough to accelerate growth.

3 articles · Updated · The New York Times · Jun 17

Days after crews finished the $14.2 million Lincoln Memorial Reflecting Pool overhaul ordered by President Trump, late-night hosts seized on the water turning green with algae.
Experts cited by Jimmy Kimmel said the dark blue waterproofing used in the project retained more heat, worsening conditions for algae growth in the pool.
Kimmel framed the bloom as a failed attempt to make the pool “American flag blue,” joking it had instead become “Mexican flag green” and a newly built swamp.
Jimmy Fallon joined in, comparing the result to “Shrek” instead of “Avatar,” turning the fast-emerging algae bloom into a broader punchline about the project’s failure.