Metro has set a Sept. 20 opening date for the problem-plagued Paul S. Sarbanes Silver Spring Transit Center, which is millions over budget and years behind schedule. (Katherine Frey/The Washington Post)

After years of delays and millions of dollars in cost overruns, officials on Thursday declared the problem-plagued Silver Spring Transit Center “ready for operations” and set a Sept. 20 opening date.

Montgomery County sent Metro a letter of transfer, detailing the completion of the three-level, $140 million commuter hub, which has been plagued with construction and design flaws. Metro has 10 days to formally accept the facility, but the transit agency said it does not expect any delay in the takeover.

Metro spokesman Dan Stessel said Thursday that the transfer “is expected imminently.”

Concerns about the strength of the concrete and the adequacy of steel supports in some areas of the facility, including persistent cracks in the concrete structure, turned the project into a major embarrassment for the county and, in the end, put the project $50 million over budget and four years behind schedule.

“We are mostly pleased with knowing that the problems that have been identified have been completely repaired; that it is a safe and durable facility that will be enjoyed for years to come and be a significant component of the regional public transportation network,” said David Dise, the county’s director of general services. “We are now delivering what we had intended to deliver all along, which is a safe and reliable facility.”

The problem-plagued Paul S. Sarbanes Silver Spring Transit Center is seen in this May 5 photo. (Katherine Frey/The Washington Post)

Metro said it plans to spend the next four weeks completing preparations for operations, training drivers and notifying riders of associated service ­changes.

This week, buses could be seen going in and out of the still-fenced site while workers cleared debris and construction equipment, and otherwise prepared the center for operations.

Metro had said that it would not accept the facility unless it was satisfied with the repairs, and as recently as last month, it raised concerns that recent fixes were showing “signs of degradation.” The transit agency had asked the county for $15 million to cover maintenance and repairs, and to relinquish to Metro its 25 percent interest in any future development on the land adjacent to the transit hub. The agency later withdrew those demands.

Dise said the county is confident that it has thoroughly addressed the problems.

Stessel declined to comment Thursday on the demands or concerns about the need for more repairs. He said Metro was “working cooperatively with the county to ensure that Metro riders and taxpayers are protected.”

Dise said that if Metro wants to pursue a long-term warranty or maintenance fund, it would have to seek it from the project’s contractors. The county is gearing up for a legal battle over the troubled project, planning potential lawsuits over the design and construction of the center.

“We will hold those whom we believe to be accountable for this problem liable for the cost of making the repairs,” Dise said.

Project designer Parsons Brinckerhoff, general contractor Foulger-Pratt and inspection firm Robert B. Balter, responsible for overseeing the quality of the concrete, have said they did nothing wrong.

The Paul S. Sarbanes Silver Spring Transit Center, with 32 bus bays, will be a hub for Metrobus, Ride-On, MTA commuter buses and other intercity bus services, serving thousands of commuters who make transfers in downtown Silver Spring. The transit center will offer a link to the Silver Spring Metro and MARC stations.

Transportation officials say the transit center will improve traffic along Colesville Road and Georgia Avenue, one of the county’s busiest bus hubs. The consolidation of all bus lines in one place should also help improve pedestrian safety, keeping people from crossing six-lane roads to catch a bus or walk up the hill to Wayne and Dixon avenues and Bonifant Street, where the county established bus stops during the construction.

Earlier, Aug. 23 — one of four days during the year that system­wide bus service changes take effect­ — had been targeted as an opening date. But because the transfer to Metro had not yet occurred, the date had to be pushed back.

Metro is taking over the facility at a critical point for the transit agency, which has come under fire in recent months for safety missteps and financial problems. It also is under scrutiny from a number federal agencies, including an investigation into a fatal Jan. 12 smoke incident in which a rider died and an Aug. 6 derailment that was caused by a track defect that had been detected a month earlier.

While Metro was not responsible for the construction of the transit center, it will be charged with its operation — and with ensuring the public that it is safe to use. As the opening nears, some riders remain skeptical.

“I will be leery of going in there once they put the weight in there of all the buses,” said Kenneth Swilley, an Upper Marlboro resident who transfers to a county Ride-On bus upon exiting the Metro station.

“Appearance-wise it looks like it will be user-friendly, but the question in my mind still stands: Is it structurally sound?” he said. “Do I have to worry about one day it collapsing?”