The Silver Spring Transit Center site at the corner of Colesville Road and Wayne Avenue. The project is on hold indefinitely. (Katherine Frey/The Washington Post)

A series of design and construction failures — including inadequate concrete strength and a lack of reinforcing steel — have left the Silver Spring Transit Center unsafe and unusable without major repairs, Montgomery County officials said Tuesday.

The problems go far beyond what was previously known and will keep the opening of the $112 million bus-and-train hub, already two years behind schedule, on hold indefinitely. Officials could not say how much it would cost to fix the issues or who would be liable.

“The problems are myriad and complex,” said David Dise, the county’s director of general services, who presented a long-awaited consultants’ report on the three-story facility to the County Council on Tuesday afternoon.

The findings are an embarrassing setback for the county in its efforts to transform Silver Spring into a genuine urban center, one less dependent on automobiles. The concrete structure at Colesville Road and Wayne Avenue, formally known as the Paul S. Sarbanes Transit Center, is envisioned as a central hub for buses, Metrorail, MARC trains, cabs and bikes.

The structural problems also place the county in a potentially difficult position with the Washington Metropolitan Area Transit Authority, which is supposed to assume control of the facility when it is finished. County officials made certain to point out Tuesday that WMATA signed off on the center’s design. But in light of the project’s condition, county officials fear that the agency could refuse to take it over or insist that the county remain on the hook financially should future problems emerge.

The report, commissioned by the county from KCE Structural Engineers, attributed the problems to “errors and omissions” by the designer, Parsons Brinckerhoff; the general contractor, Foulger-Pratt; an inspections firm, Robert B. Balter Co.; and other subcontractors.

Montgomery officials asked for the report last summer after cracks emerged in concrete slabs. But the 100-page KCE report and supporting exhibits make clear that the problems go far beyond cracking.

Much of the consultant’s focus was on the second level of the building, intended to be the main travel route for hundreds of buses each day. KCE said Parsons Brinckerhoff’s design caused supporting steel cables within the concrete to become “over-stressed,” or wound too tightly. It was this pressure that caused the cracking in the concrete — and the exposure of steel rods — that triggered the initial concerns of county officials in 2011.

The cracking was compounded because concrete in various parts of the second level was not up to specifications, according to the report. Tests showed that concrete used by a subcontractor hired by Foulger-Pratt had a strength of 6,970 pounds per square inch. The contract called for a strength of 8,000 psi. The concrete was also not thick enough at various locations.

Most alarming, county officials said, was the absence of reinforcing steel in two critical 10-foot-by-40-foot slabs in the center of the bus roadway. Had the lack of steel gone undetected, the roadway could have failed, dislodging large chunks of concrete from the first-floor ceiling onto pedestrians and vehicles below, county officials said. KCE placed this failure directly on Foulger-Pratt.

“Regardless of other deficiencies on the project, this defect results in an unusable facility — a significant safety hazard,” a summary of the report said.

County Executive Isiah Leggett (D) said in a statement that the facility is “severely compromised” but vowed that it will open.

The opening of the $112 million bus-and-train hub, already two years behind schedule, is on hold indefinitely.

“I pledge that the County will move forward aggressively to ensure that needed repairs are made to get the SSTC open as soon as possible,” Leggett said.

Jerry Jannetti, Parsons Brinckerhoff’s vice president and area manager, said he would have no detailed comment on the report until he had a chance to review it. “This project has had a fair amount of issues and a fair number of participants,” Jannetti said. “I think that all those involved are trying to understand what to do next.”

Bryant Foulger, managing principal for Rockville-based Foulger Pratt, who attended Tuesday’s council briefing, also said he would have no comment.

Asked if he was dismayed by the findings, he said only, “We’re good.”

One major project participant that did not come in for scrutiny was the county itself. Dise said that was appropriate and that the inspection firm it hired to oversee the work — Robert B. Balter Co. — was responsible for matters such as ensuring that the concrete was of adequate quality.

He described the county’s role as that of a homeowner commissioning a project.

“Like any owner, we try to hire the best people we can,” Dise said. “When they don’t work out, like any owner we have to deal with that.”

The county broke ground for the center in 2008, with plans to open it in 2011. But county officials raised concerns about cracks in the concrete, the thickness of some elevated slabs and the adequacy of the reinforcing steel. Although the project is largely complete, disputes about the nature of the problems, their long-term importance and who is accountable have brought the venture to a halt.