WASHINGTON – One hundred and twenty-nine feet above the ground, the dome of the Jefferson Memorial yields panoramic views of the White House, Washington Monument and the Lincoln Memorial from across the Tidal Basin.
But these views are not accessible to the public, just to the construction workers who have been renovating the roof and cleaning the iconic memorial’s dome since February.
The memorial sees thousands of tourists and Washingtonians sit on its steps each spring to enjoy the pink cherry blossoms blooming around the Tidal Basin. This year, the memorial will be covered in scaffolding for the National Cherry Blossom Festival as workers continue to remove a strange substance that has dirtied the dome for years.
The Jefferson Memorial’s exterior marble has been covered by what specialists call a dark biofilm for the past 13 years. Biofilm is a fairly new phenomenon – there isn’t much existing research or technology to reference.
But the stuff is tough, resisting countless chemicals and cleaners. Now the National Park Service is testing lasers to clean the marble.
Environmentally, using lasers is much safer than using chemical-based solutions because chemicals could pollute the Tidal Basin.
The memorial is in its ninth month of the 15-month cleaning project, projected to conclude in May, but the work could extend beyond that.
Besides cleaning the marble, the project includes fixing the dome roof and repairing the stone.
The renovation contract requires the memorial to remain open for the duration of the project, although the east side of the memorial will be inaccessible, said Keith Ramsay, a consultant for the National Park Service who oversees the contract. The public can walk inside the memorial easily beneath the scaffolding.
The black biofilm growing on the top of the memorial is a microbial colony of algae, fungi and bacteria. Biofilm is attracted to the nooks and crannies of the marble and needs ultraviolet light and moisture to grow.
The park service has studied this growth since 2014 to determine the best treatment options.
The black biofilm has appeared on a number of other memorials and government buildings, including the Lincoln Memorial, the Arlington Cemetery Amphitheater and some Smithsonian Institution buildings. But nowhere is it as pronounced as on the Jefferson Memorial.
Based on testing conducted by the park service, lasers will remove a lot of biofilm, but it is not certain if and when it’ll grow back.
The Arlington Cemetery Amphitheater is made out of the same marble but has a different type of biofilm on its exterior, so a zinc oxide wash is being used to block sunlight from enabling the biofilm to grow.
The park service is monitoring the biofilm cleaning at Arlington and comparing it to the Jefferson Memorial, said Historic Architect Audrey Tepper. The park service is working on a long-term plan to analyze how the biofilm grows.
“We’re prepared that this might not be a long-term solution but hoping for long mileage out of this (laser) treatment,” said Tepper.
Lasers are very specialized and take a lot of calibration, sequencing and timing. A lot of preparation is required to clean the marble before using the laser. It is a time-consuming process, only cleaning 2 square feet per hour.
The contract for this work was awarded in September 2018 to Grunley Construction for $8.75 million, but National Mall and Memorial Parks spokesman Mike Litterst said the total cost could increase if issues arise. In that case, additional funds would come from the park service’s appropriations.
Biofilm is still a relatively new problem, so there is not a universal solution, Litterst said. The park service typically cleans the monument with a soft power wash several times each year, but that was not strong enough to remove the biofilm.
The park service looked at a number of different solutions, most of which were chemical-based. The agency picked lasers based on testing, which revealed that the biofilm would not grow back imminently.
The memorial stands not far from the White House. It honors the country’s third president with classical architecture, evocative of Jefferson’s home, Monticello, and the rotunda at the University of Virginia, which he founded.
Jefferson also was the primary author of the Declaration of Independence and the nation’s first secretary of state.
Monticello Vice President Andrew O’Shaughnessy is writing a book on the history of Jefferson’s founding of the University of Virginia. He said it is important for the memorial to be restored to commemorate the man who played an integral role in America’s founding and wrote the nation’s “mission statement.”
John Ragosta, a historian at the Thomas Jefferson Foundation, studies Jefferson in the early republic as well as Jefferson’s role in leadership, religion and education.
“I think far more important than the architecture is what is written on the panels of the memorial,” Ragosta said. “He tells us what Americans are, but I like to say he speaks of what Americans want to be.”
The first panel of the memorial quotes the Declaration of Independence: “We hold these truths to be self-evident: that all men are created equal, that they are endowed by their Creator with certain inalienable rights, among these are life, liberty, and the pursuit of happiness, that to secure these rights governments are instituted among men.”
Ragosta acknowledged Jefferson’s contradictions as a slave-owner, but noted that his vision for America was cited by Dr. Martin Luther King, the Black Panthers and suffragettes.
“When one goes to the memorial, you’re seeing what America wants to be,” Ragosta said.