The Silver Spring Transit Center will need additional extensive repairs before it opens to the public, officials say. (Sarah L. Voisin/The Washington Post)

Montgomery County officials have determined that the troubled Silver Spring Transit Center, which is two years behind schedule and tens of millions of dollars over budget, needs even more extensive repairs before it opens to the public, officials said Tuesday.

In addition to fixing cracks that appeared throughout the three-level structure, project contractors need to strengthen about 250 interior beams and girders to stand up to heavy bus traffic at the transit hub, according to the county’s general services director, David Dise.

Dise told the County Council that the additional work will not further delay the project, which broke ground five years ago. Estimates are that it will be mid-2014 at the earliest before the center is opened. The center, at Georgia Avenue and Colesville Road, will bring together Metro, Ride On, MARC, Amtrak, intercity bus lines, taxis and other transportation services.

Dise’s disclosure raised fresh questions about the original design of the facility by Parsons Brinckerhoff, an international engineering firm. Two engineering consultants, one hired by the county and the other by Metro, said this year that the center’s design was too rigid, leaving little room for natural movement and increasing the likelihood of serious cracking.

Dise attributed beam and girder problems to Parsons Brinckerhoff.

Concrete issues at the Silver Spring Transit Center

“It would appear to be a design error,” Dise said.

In a statement, Jerry Jannetti, a Parsons regional vice president, called the county’s conclusion “unfortunate” and said beams and girders needed no extra support. “We remain committed to opening a safe and durable transit center as quickly as possible,” he said, “but believe that the County’s decision will prolong the opening at needless expense.”

The beam-and-girder issue was first raised in March by KCE, the engineering firm hired by the county to investigate cracking in the largely concrete facility.

Asked why it took an additional eight months to conclude that the beams and girders would have to be reinforced, Dise said other challenges — including problems with concrete thickness and lack of steel supports in key roadway segments — needed to be resolved first.

Dise also said that the county asked Parsons in April for its original design calculations on the beams and girders but that it was late October before the firm responded.

At a meeting Nov. 8, Dise said, Parsons revealed that it had not factored “torsion and shearing” into its calculus. Torsion is the force exerted by twisting; shearing refers to vertical pressures that could cause concrete to crack or fail.

Parsons engineers said the American Concrete Institute did not require torsion or shearing calculations for such a design. KCE and the county maintain that in view of the project’s troubles to date, it was prudent to take those forces into account.

The reinforcement will involve adding additional supports.

The disclosures are likely to make the transit center more of an issue in the 2014 county executive’s race. It figured prominently in a Rockville campaign event attended Monday evening by County Executive Isiah Leggett (D) and one of his two challengers for the Democratic nomination, former county executive Douglas M. Duncan.

Duncan decried the lack of accountability for delays and all but called for Dise to be fired.

“We need to hold someone accountable for this,” he said. “We need to fix the Department of General Services. The Department of General Services is broken.”

Dise declined to comment.

Leggett, who spoke first Monday, volunteered without being asked that responsibility rested with him. But he said the delays were a product not of lax oversight but of his insistence that all questions be answered fully before the center opened.

“I had a full-scale investigation into what some deemed to be a minor problem,” Leggett said. It was a not-so-subtle slap at the general contractor, Foulger-Pratt, which advocated a patching procedure that was ultimately rejected by KCE.

On Tuesday, County Council members reiterated their dissatisfaction with the problem-plagued trajectory of the project.

“This has been the biggest construction debacle in the county’s history,” said council member Phil Andrews (D-Gaithersburg-Rockville), who is also running for county executive.

The council also heard from Dise on the cost of changes to the project in the course of construction. Responding to a request from Andrews, Dise reported 450 requests for changes from contractors since the beginning of the project, many caused by conditions at the construction site or related to to design issues.

The 450 requests were bundled into 17 change orders, totaling about $11 million in additional costs. Dise said that change orders are a part of every big project but that they occurred on this project at about twice the usual rate.