About 1,300 cracks crisscross the cast iron shell of the Dome, constructed 150 years ago, and more than 100 pieces have been removed to keep the grounds safe from falling debris since the last total restoration, completed in 1960.
Ayers announced the restoration project in October after AOC awarded a joint $40.8 million contract to two construction companies, Turner and Smoot. Since then, contractors and a team of consultants have been awarding subcontracts and reviewing scaffolding designs, materials and methods of work.
“Like any project that you might do in your home, it’s the planning and preparation that takes as long as the work itself,” Ayers said.
With help from the National Institute of Standards and Technology, the team identified the strongest and most viable technique for workers who would be stationed 200 feet above the ground. Rather than welding, workers will use a mechanical “lock and stitch technique” of drilling out cracks and stitching them together with a series of steel pins.
They are also making plans to strip off about a dozen layers of lead-based paint that must be captured and contained. To do so, paint blasting will be done in phases, inside white enclosures that would move around the Dome over the course of two years.
Planning continues, and construction timelines are still being finalized.
Inside the Rotunda, workers will construct a covered walkway to protect those travelling between the House and Senate chambers. A 96-foot walkway will shield passersby as workers install a doughnut-shaped canopy to protect the project. Some of the artwork will be covered, too.
About 100 feet above the floor, workers will remove 11 of the window panels ringing it to install a system of rigs that will support the protective fabric doughnut. The fabric will stay in place for the duration of the project, while still allowing views of “The Apotheosis of Washington” fresco, depicting President George Washington on his ascent to the heavens.
Outside, workers will install vertical scaffold towers on the West Front. Then, they will construct scaffolding that bridges over the West Front terrace and erect a work platform around the roof of the Capitol. Rings of scaffolding will then begin to extend up from the base of the Dome.
Ayers said the scaffolding is one of the riskiest parts of the process.
“Getting all that scaffolding here, lifting it up to the roof of the Dome and then getting it installed and taken back down is just a massive logistical effort that’s probably one of the biggest risks on the job,” he said.
Luckily, AOC learned some lessons about working on the structure during a 2012 restoration of the Dome skirt, including how to complete a project on time and on budget and also which repair techniques are best suited to the historic structure.
After you take all the paint and primer off the dome, Ayers said, “the cast iron of this generation flash-rusts in eight hours,” so the timely application of new, gleaming white paint is essential. “We have to have those processes down so we don’t have to do repeat work,” he explained.
After explaining the ins and outs of the project, Ayers was asked if he could guarantee that the project would not exceed the $59.55 million budget.
“Guarantee — that’s a big word,” he quipped, “but we’re pretty confident — I’ll give you that.”