WASHINGTON, Sept. 26 (UPI) -- The Washington Monument will remain closed indefinitely because of problems with its elevator.
The 555-foot monument has been closed since August because of elevator breakdowns.
"We have not been able to determine the causes of the ongoing reliability issues," said Mike Litterst, of the National Park Service, in a statement Monday. "As a result, we have made the difficult decision not to reopen the Washington Monument until we can modernize the elevator control system."
In an email to The Washington Post, Litterst said "it's a long-term closure, one that will be measured in months."
The sole elevator runs from 9 a.m. to 5 p.m. every day, except in summer when it runs from 9 a.m. to 9 p.m. "It's in constant use, which certainly adds to its stresses," Litterst said.
The elevator had problems even before the monument was damaged by a 5.8-magnitude earthquake in 2011.
It cost about $15 million to repair the monument and involved 500 tons of scaffolding. Funding included a $7.5-million donation from local businessman and philanthropist David M. Rubenstein for the three-year project.
The elevator is 15 years old and has outdated mechanical and electrical systems. And Litterst said moisture may have gotten into cracks and into mechanical areas because of the earthquake.
The monument closed on Aug. 13 because of computer issues, which affected the elevator's control system, Litterst said. Two employees and one park service volunteer were trapped in the elevator for about 40 minutes. Also, 73 visitors on the observation deck were evacuated via stairs, which number 897 total.
The next day, one National Park Service employee became stuck in the elevator at the 490-foot level. The worker got out after the doors were reopened and walked down the steps. About 50 people walked down the steps from the observation level.
Independent consultants brought in couldn't determine exactly what was causing all the problems, Litterst said.
The monument's stairs were closed for walking up in 1971 and totally in 1976 except for special circumstances, Litterst told The Washington Post last year.
The climb, estimated at 46 stories, used to take about 20 minutes to go up and 10 to go down.
Around 600,000 people visit the monument each year. Construction began in 1848 and was done in 1884.
Litterest called the shutdown "tremendously frustrating" for visitors and staff.