With one in six escalators now under repair, the Metro system plans to augment its own workforce with an outside contractor to speed work on 74 Orange Line escalators and elevators, General Manager Richard Sarles said Tuesday.

Officials at the transit agency are expected to make a presentation on Thursday to Metro’s board of directors on their plan to hire an outside contractor to do preventive maintenance on 54 escalators and 20 elevators on the Orange Line from Rosslyn to Vienna. Altogether, the system has 588 escalators, more than any other transit agency in the country.

Sarles said the additional manpower will “supplement the existing staff” of roughly 200 in-house employees who now work in the escalator and elevator division.

“We need more people,” Sarles said. “Rather than attempting to hire more people who then have to go through a multi-year training effort to be brought up to full speed on doing repair and maintenance, we can go out to seek qualified contractors to do the work.”

Over the years, Metro has alternated between staff and contractors to perform escalator maintenance and repairs. Along the way, it has dumped tens of millions of dollars into its equipment and hired consultants to do studies of whether in-house or contracting out is better, all without finding a lasting solution.

Metro’s escalator and elevator division has 147 mechanics; 49 people who work in management, inspections and support; and 12 maintenance supervisors. It also has an in-house apprenticeship program that trains escalator and elevator mechanics in doing daily repairs and maintenance. Major overhaul and replacement work on escalators is now mostly done by contractors, as part of its capital improvement budget, officials said.

In the past, Metro has defended its mechanics and training program and gave a pay increase to try to stem high turnover and competition from private industry for mechanics.

The transit agency’s union — Amalgamated Transit Union Local 689 — was skeptical of the new contracting plans.

“[Metro] has thrown so much money into the elevator-escalator department, but they haven’t tried to go out and try to hire enough mechanics,” said Jackie Jeter, the union’s president.

Metro’s escalator and elevator repair division has long had troubles.

In 1997, an investigation revealed that escalator maintenance records had been falsified. Nine escalator supervisors and top managers at the agency were fired, demoted or suspended.

Last year, a consultant — Vertical Transportation Excellence — found that Metro was not adhering to its own maintenance standards. After an escalator incident injured six people at L’Enfant Plaza, Metro launched a systemwide inspection that led to multiple emergency repairs.

Fixing the escalators is a vexing problem.

The transit system depends on escalators more than other rail system because its stations are deep below the ground and there are few staircases. Seventy-five percent of its 588 escalators are over 25 years old and parts can be difficult to find because four of seven manufacturers have gone out of business. Many of the escalators have not been properly maintained over the years.

For the last eight months, Metro has done required preventative maintenance on schedule less than 60 percent of the time. Sarles said he would like to get that number to 85 percent. On Tuesday afternoon, Metro’s Web site reported 103 escalators “under repair.”

Sarles said he hopes to have the new contractor in place by the beginning of next year. Metro officials would not reveal the expected ceiling price of the contract because they said it is a competitive process.

With additional workers, Sarles said Metro’s employees who work in its escalator and elevator division can concentrate on doing repair and maintenance work on other lines in the rail system.

Metro said the new proposal fits into its longer plan to spend more than $153 million to either buy new, rehabilitate or replace about 180 escalators and elevators. In July, it opened the first of three brand-new escalators at Foggy Bottom, the first time in more than a decade that Metro has installed a new escalator in an existing station.

Staff researcher Jennifer Jenkins contributed to this report.