Restrooms and mechanical systems will also be upgraded.
The National Park Service has already embarked on an $8.2 million project to restore the exterior of the tattered landmark, which has grown dingy in recent years from the advance of a black biofilm of algae, fungi and bacteria, as well as other effects of its exposure to the District’s weather, climate and insects.
Rubenstein — co-founder of the Carlyle Group, a global private-equity firm based in Washington — is passionate about U.S. history and has made numerous major history-themed donations in the past.
The 32,000-ton Jefferson Memorial remains open, and the external work should be finished by next spring, the Park Service has said.
The memorial sits on fill dredged in the late 1800s from the Potomac River, and on 634 pilings and caissons sunk down to bedrock on the south side of the Tidal Basin. One support goes down through 138 feet of soft earth.
Over its seven decades of life, the structure has been affected by the vagaries of its location and the capricious piece of ground on which it sits.
As early as 1941, two years before its dedication, some of the supports under the memorial’s main steps began shifting. They had to be lashed together with steel cable and turnbuckles, according to an engineering report done for the Park Service in 1965.
Settlement also caused other supports under the steps to bend slightly, the report says. The steps moved so often that park rangers once kept a special tool at the site to realign them, the report says.
Lesser settlement continued during the 1940s and ‘50s.
By the 1960s, the front plaza, which was not supported by pilings, began to sink — by as much as three feet — and a $1.1 million engineering project was undertaken to bolster it with more pilings and supports.
In 2010, a $12.4 million repair project shored up the memorial’s poorly supported sea wall, which also had been sinking into the tidal ooze.
Last year, Rubenstein announced a donation of $18.5 million to help fund what is probably the biggest overhaul of the Lincoln Memorial since the structure was dedicated almost a century ago. The project began in 2016, and the Park Service hopes to have it finished for the memorial’s 2022 centennial.
In 2015, Rubenstein pledged $5.37 million to refurbish the U.S. Marine Corps War Memorial, the 100-ton bronze sculpture of the flag-raising at Iwo Jima during the war.
He has also donated $5 million to the White House Visitor Center; $12.3 million to Arlington House, the home of Robert E. Lee; and $7.5 million to help fix the Washington Monument after the 2011 earthquake.
The donation for the repairs of the memorial will go to the National Park Foundation, which will distribute the funds.
“Hopefully what we’ll be able to do is make the experience of visiting the Jefferson Memorial even better than it has been,” Rubenstein said as he sat at a table before the memorial Tuesday afternoon.
“While Thomas Jefferson is not without some things that we can question today, clearly he did some great things for our country,” he said.
“A very incredible person, a great intellect, a great Renaissance man and one of our greatest Americans, so I’m very pleased to be able to do this,” Rubenstein said.