B2 EZ RE THE WASHINGTON POST.TUESDAY, OCTOBER 26 , 2021
that beautiful smooth surface
becomes eroded and it has a
topography. That texture pro-
vides a surface that will stay w et
for longer periods of time from
rain, condensation, mist. This
provides just the perfe ct environ-
ment for microorganisms.”cob, is that the Jefferson Memo-
rial’s marble surfaces have
weathered over the years.
“Rain alone will slowly erode
the surface,” Jacob said. “New
marble has a sanded or rubbed
finish with a satin sheen to it.
That will erode first. With time,What’s next?
As restor ation jobs went, this
was never going to be one of
D.C.’s big gest — t he $14.5 mil-
lion budget to restore the Jeffer-
son Memorial is dwarfed by, for
example, the $60 million resto-
ration of the Capitol dome in- Still, as the nature and
extent of the biofilm infestation
became clear to analysts, it also
became clear that this job would
eat every dime they had allocat-
ed and contingency funds as
well.
And as anyone who’s stood in
the swamp-like murk of a Tidal
Basin summer day will hardly be
surprised to hear, it’s a j ob they
will be doing again. “We think
this biofilm will come back, and
we are continuing to study it,”
Tepper said. And they’re not
alone.
Conservators across the Poto-
mac at Arlington National Cem-
etery are dealing with similar
biofilm on their Memorial Am-
phitheater, which is built of the
same Vermont marble as the
Jefferson Memorial. The Folger
Shakespeare Librar y’s ongoing
$72 million renovation includes
abating biofilm discoloration
from its facade, constructed of
slightly softer Georgia marble.
The D.C. War Memorial on
Independence Avenue across
the Tidal Basin from the Jeffer-
son Memorial also features a
Vermont marble dome, visibly
afflicted with an extensive —
and growing — biofilm infesta-
tion.
Government funding address-
ing maintenance shortfalls at
National Park Service proper-
ties, specifically the 2020 Great
American Outdoors Act, along
with the agency’s usual dexterity
in working the government’s
patc hwork funding channels,
le aves NPS officials cautiously
confident that when dark
splotches reappear on the Jeffer-
son Memorial dome — “when,
not if,” as Tepper put it — they
will be able to respond.
And as for how soon that
might happen?
“I have no guess,” said Jacob.
“We’ll just have to wait and
see.”
[email protected]
Aaron Steckelberg contributed to
this report.with all marble monuments. Con-
servators suspect this process
gave the biofilm greater purchase
— more nooks and crannies in
which to flourish and thicken.
By the spring of 2016, the
thickening biofilm began to
darken, discoloring the white
dome in unsightly — and grow-
ing — p atches.
Conservators employed a
two-stage process. First, they
used carefully calibrated pulsed
laser beams designed primarily
to target pigmented biological
cells. Think of them as the big
brothers of the lasers sometimes
used to remove tattoos. This
process, never before attempted
on this scale, reduced the pig-
mented biofilm to a fine ash.
Second, conservators went to
work with gentle, low-volume
steam cleaning jets to blast the
biofilm ash — along with pigeon
droppings and any other accu-
mulated sediment — out of the
marble’s cr evices.
The result is a dome that, at
least from Independence Avenue
or the windows of approaching
airliners, appears as good as new.
Why the sudden change?
No one knows for sure why
this biofilm only became a visible
problem over the la st 20 percent
of the Jefferson Memorial’s life.
One theory suggests that hydro-
carbons from partially combust-
ed jet fuel might feed the infesta-
tion; increased traffic into Rea-
gan National Airport over the
past couple of decades might
explain the change.
Cleaner air may also be to
blame: Since the enactment of
the federal Clean Air Act in the
1960s, the amount of particu-
lates in the air has lessened. The
cleaner air has allowed more
ultraviolet light to reach the
dome’s surfa ce, possibly feeding
the biofilm colony.
And the specter of climate
change may offer an explanation.
Summers are generally longer
and hotter now than they were
years ago. Could this be having
an effect? Park Service conserva-
tors would love to know. “We
need more people studying this,”
Tepper said.
One thing preservation ex-
perts do know, according to Ja-
MEMORIAL FROM B1
In D.C., a $14 million makeover — with lasers, cleaning jets
MICHAEL S. WILLIAMSON/THE WASHINGTON POST
Splotches of biofilm mar th e Jefferson Memorial’s dome in 2019 as Tonia Rivers, a senior project manager at Grunley Construction,
surveys the cleaning and repairs. Audrey Tepper, a Park Service architect, said it’s a question of “when, not if” the film will reappear.MATT MCCLAIN/THE WASHINGTON POST
Biofilm similar to the kind that spread on the Jefferson Memorial
dome can be seen atop the D.C. War Memorial on Oct. 19.“It’s a microbial community of bacteria, fungi and
algae.... It occurs all over the place.
It’s existed for eternity, but it’s more visible on
white marble buildings.”
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