(CNN) -- The Washington Monument will remain closed for repairs for at least another year and possibly into 2014, National Park Service officials said Monday.
The 555-foot-tall monument has been closed since an earthquake struck the mid-Atlantic region near Richmond, Virginia, in August 2011. Repairs are expected to begin this fall.
The service said that huge scaffolding will be needed for the outside repair work, which will take 12 to 18 months to complete. Some of the repair work will include sealing cracks, removing loose pieces of stone and repairing joints.
"The challenge is most of those cracks are at the very top portion of the monument and the ability to get workers up there to successfully repair it requires a major scaffolding effort," said Bob Vogel, superintendent of the National Mall and Memorial Parks. "The monument is in good shape. It's going to be here for years to come, but in order to safely allow visitors to get up to the top, we need to make those repairs."
At least nine of the marble panels on the exterior near the top are cracked, according to a post-earthquake assessment. Others are chipped but not in danger of falling, the report said.
About 700,000 visitors go to the top of the monument in a typical year, Vogel said.
"It's very disappointing," he said. "I hear from people everyday asking how they can get into it."
Isaac Boria came from Port St. Lucie, Florida, with his wife and two children. Seeing the view from the top of the monument was high on their to-do list.
"That's Mother Nature, " he said. "Mother Nature did its thing, and I'd rather be safe than sorry."
Indoor repairs are also required. Some interior tie beams as well as some cracked panels will be fixed.
A pedestrian walkway will be redirected to make room for a temporary road for construction vehicles.
The 5.8-magnitude earthquake may have also caused the structure to sink a little.
In September, the monument was declared structurally sound by engineers.
David Rubenstein, co-founder of the investment firm The Carlyle Group, has donated $7.5 million toward the repair project.
With Rubenstein's donation and congressional funds that were approved in December, Deputy Interior Secretary David Hayes said in January there was enough money to begin the repairs.
The Washington Monument was built between 1848 and 1884 and has been repaired three times previously, the most recent work done from 1997 to 2000.
CNN's Eric Fiegel and Lindy Royce contributed to this report.