The  U.S. Capitol Dome is about to undergo a two-year, $60 million restoration project that, much like the one at the Washington Monument, will cover the iconic structure with scaffolding.

The cast-iron dome, constructed 150 years ago — and championed by then-Sen. Jefferson Davis (D-Miss.) until he went off to run the Confederacy — has not had a complete renovation since 1960, according to the Architect of the Capitol, and age and weather have caused more than 1,000 cracks and other “deficiencies.”

The architect’s office is constantly working at restoration of the Capitol. They’re now doing an extraordinary restoration of the murals on the first floor of the Senate side of the Capitol, tediously retouching the walls to restore them to their original 19th century design.

“A lot of the work on this project will be done at night so as not to interfere with the work of Congress,” architect office spokesman Justin Kieffer told us. (These days, of course, polls are indicating it might be just as well to go ahead and work on the dome during the day.)

“A white canopy system in the shape of a donut” is going to be installed to protect the public, the architect’s office announced. That would allow the center of the Rotunda to be visible during the restoration project.

The project “is long overdue,” said our former colleague Guy Gugliotta, author of Freedom’s Cap, the story of the building of the dome in the shadow of the impending Civil War.

“There’s been a lot of water under the eaves” since a storm in the 1990s caused water to leak down onto the rotunda floor, he said. A lot of lawmakers were most upset by that and a 1998 study laid out what needed to be done. But a lot more damage and many more cracks — not to mention bird poop —  accumulated in the meantime until Congress agreed to move on it.

And it’s going to be a very difficult project, because cast iron doesn’t weld. “It melts,” Gugliotta noted, so “they’re going to have to use low-tech methods, like drilling the cracks and filling them with metal plugs, and to master those techniques before they begin. Failure is not an option. This is the U.S. Capitol.”