The satellite images above were provided by Vantor Technologies. They compare how the DC Reflecting Pool looked like 3 years ago (and pretty much does again now), and the way it briefly looked after it was resurfaced with a sealer colored “American Flag Blue.” It didn’t last very long for several reasons.
The short answer is something hydrologists call New Pond Syndrome. Bodies of water that are shallow often struggle with this, and the Pool is only 30 inches deep at its center, sloping to 18 inches along the edges. Plus, it’s not shaded and is exposed to bright sunlight all day long. Finally, it’s visited (and excreted in) by many birds every day. It has a robust filtering system, but even so, these are perfect conditions for the growth of algae. Especially when you disturb an existing stable ecosystem with resurfacing.
Further, the “American Flag Blue” coating absorbs more sunlight that the original gray concrete. That raises the temperature of the water which accelerates algal growth. Even though the Pool measures 2,030 x167 feet, and contains some 6.75 million gallons of water, it took only a matter of days for the new water to become clouded with algae.
The water was tested by experts and found to harbor an algae called Desmodesmus. It’s green because it contains cloroplasts that convert sunlight, carbon dioxide, and water into glucose and oxygen — same as in the leaves of trees. It consists of colonies of two, four, eight or 16 cells arranged in a row. Cells are ellipsoidal to ovoid, joined to each other by their longer sides. The terminal cells of a colony (and sometimes the medial cells as well) are usually armed with spines. It’s not toxic to humans or wildlife (like the many ducks the frequent the Pool), but it sure looks ugly and can clog the filtration system. This is what Desmodesmus looks like under a microscope:
The National Park Service is taking several steps to remediate this problem. First, they’re adding hydrogen peroxide to the Pool. It’s a milder treatment than chlorine and is used in spas and pools. There are no harmful side effects to humans, birds, or the environment.
Workers are also deploying what the NPS calls “high-tech nanobubble ozone technology” to neutralize algae and other pathogens in the pool. NPS says that approach is validated by several universities and the National Oceanic & Atmospheric Administration. Those microscopic bubbles (you can’t even see them) are neutrally buoyant, so they won’t just rise to the surface and disappear readily. They can last for weeks, if not months in the water. Ozone is a strong oxidizer and efficiently kills algae.
Ultimately, the pool may need to be restored to its original concrete-gray color. Alas, the project has already cost near $14 million — $1.7 million of that just for the nanobubble technology. This is clearly uninformed planning and poor management. The NPS needs to consult with some hydrology experts.
Next Week in Sky Lights ⇒ What an Aurora Looks Like From the ISS