A biological growth is making the Thomas Jefferson Memorial appear black, filthy and grimy in spots. And this week the National Park Service began tests to see if they can find a way to remove the spreading grime.
WASHINGTON — Visitors who walk up to the iconic Thomas Jefferson Memorial in D.C. might see the monument and think it is dirty, but what they are actually looking at is a collection of microorganisms known as a biofilm.
The 73-year-old landmark is covered with the biological growth, making it appear black, filthy and grimy in spots.
“This is a really important, but very challenging topic,” said Gay Vietzke, superintendent of the National Mall and Memorial Parks. “The challenge we have is not just figuring out a solution to address it, but also helping the public understand what’s going on.”
The biofilm was first visible on the monument in 2006 and has become much more pronounced in the last decade. Since 2014, the National Park Service has been studying options to safely remove it. And just this past week, testing began to see what chemicals would work best.
“Treatment is difficult as there is no known permanent method of biofilm removal,” said Catherine Dewey, chief of resource management for the National Mall and Memorial Parks.
Using a power washer on the biofilm is not an option because it would cause severe damage to the marble, Dewey said.
“Ultimately we will choose the treatment option that is the least damaging to the stone, safe for the environment and visitors and cost effective.”
There is no timeline yet for how long the cleanup project might take to complete.