Beginning Monday and for the next three to five years, parts of the Lincoln and Jefferson memorials will be shadowed by scaffolding and fencing while the National Park Service undertakes a massive project to inspect, document and repair the two structures.

The work will infringe on two of the city's most scenic and photographed vistas -- the Lincoln Memorial framed in the Reflecting Pool, and the Jefferson Memorial rising from the edge of the shimmering Tidal Basin -- and will limit but not block visitors' access to the interior of each memorial.

The $22 million project was planned even before parts of the carved capitals from two of the Jefferson Memorial's 42-foot columns broke off and crashed to the floor last year.

"The memorials are not falling down. They are structurally sound," Park Service spokeswoman Sandra Alley said yesterday. "This is to ensure that they are there for future generations to enjoy."

Preliminary studies of the two memorials, released in April 1990, recommended the tests and repairs to assess and repair damage caused by acid rain, insects, jet fuel and other factors.

James Kren, of the Park Service, who is overseeing part of the project, said the detailed inspection also is expected to reveal more about "how the buildings appear and were built."

The inner chambers of both memorials -- including the 19-foot-tall marble statue of a seated Abraham Lincoln and the 19-foot-tall bronze figure of Thomas Jefferson -- will remain open to visitors throughout the work, Alley said.

The work will be the first time that the exterior of either memorial has been covered to any extent -- including in time of war -- since the two opened, the Lincoln Memorial in 1922 and the Jefferson Memorial in 1943.

The Lincoln Memorial and the nearby Vietnam Veterans Memorial are the most popular National Park Service structures, with more than 1.2 million visitors a year. The Jefferson Memorial attracts more than 750,000 visitors annually.

Like the Capitol, whose West Front was shadowed by scaffolding for three years in the mid-1980s, and the White House, parts of which have been shrouded during the last five years for a to-the-bones cleaning, the two memorials are required stops for virtually any tour of the nation's capital.

Many area residents stop frequently at the memorials, often at night when their stark simplicity is enhanced by brilliant floodlights, to bask in their serenity and seek inspiration.

Tourists and tour guide companies said yesterday they were surprised by news of the upcoming work.

"Every time I come to D.C., I have to come by," said Jerry Washington, 32, a machine operator from Boston who was visiting the Lincoln Memorial yesterday. " . . . I can understand them fixing it up. I have nothing against that. At least we'll know where our money is going. Some of it."

Steve Robbins, a 20-year employee of Tourmobile Sightseeing, said he believes that "there might be a lot of disappointment" among tourists once certain views of the memorials are obstructed, but he predicted that people "aren't going to postpone a trip that's been planned for weeks or months."

The project will include visual inspections of all the stones in both memorials, and sophisticated computer-assisted photography that will generate detailed drawings of the precise carving and condition of all the stones to identify any needed repairs, Alley said.

"We don't expect to find any major problems," she said, "but there will be repairs to individual stones."

Workers on Monday will begin to install heavy, six-foot-tall chain-link fences around the Lincoln and the Jefferson that will block access to the raised grass terraces around each, as well as the open colonnades that encircle each memorial, Kren said.

It will be three to five years before visitors will again be allowed in those areas, Alley said. The western side of the Lincoln's colonnade also is a favorite of photographers for its view across the Arlington Memorial Bridge to Arlington Cemetery.

Also on Monday, work will begin at the Jefferson on a bo's'n chair, which Kren described as a roped-in chair, rigged from the top of the dome, that will allow a worker to walk and lean against the dome while inspecting it.

Kren, who will oversee construction and moving of all scaffolding for the project, said work will begin Dec. 16 on a large, rolling interior scaffold at each memorial that will be used to inspect the upper reaches of the colonnade and the ceiling.

On Jan. 13, work will begin on the exterior scaffolding at both memorials, Kren said. He said that there will be four scaffolding towers at the Lincoln, one on each face of the structure, and that each will be 16 feet wide and reach from the ground to the roofline. The towers will be partially disassembled and moved along the sides of the memorial as work proceeds, Kren said. Two similar towers will be used at the Jefferson.

Plans are still being developed for additional scaffolding that will be used to inspect the areas above the entries at each memorial.

"You will notice the scaffolding," Kren said, "but it will not completely engulf the memorials."

Staff writer Christine Spolar contributed to this report.