Montgomery County Executive Isiah Leggett (D) plans to ask the County Council for more money to cover the cost of repairing the Silver Spring Transit Center, already nearly $30 million over budget with no opening date in sight.

General Services director David Dise, the lead county official on the troubled project, offered no specifics at a council briefing Tuesday. He said a request for a “supplemental appropriation” would be submitted in two to three weeks.

The three-level commuter terminal at Georgia Avenue and Colesville Road, originally scheduled to open in late 2010, has been a major embarrassment for Leggett and the county.

The additional expense could be considerable. Since early summer, contractors have drilled and excavated portions of the structure to install additional supporting steel. The “cap ties” are intended to strengthen the building against the stresses caused by the expected passage of hundreds of buses through the center each day. In a recent interview, Dise placed the cost of that work at about $1.6 million.

But more costly fixes are on the way. In coming weeks, workers will apply a two-inch layer of latex-modified concrete to roadways and other surfaces, a task that requires highly specialized equipment. The final major fix will be the addition of 255 strut beams to reinforce interior girders.

The new appropriation request is expected to include other costs, such as continued operation of the interim Silver Spring site for buses and fees for engineering consultant Allyn Kilsheimer, who was hired by the county to oversee the repairs.

Dise said he is awaiting more information on the strut beams before he can finalize the funding request.

Council members, eager to get the transit center off their agenda, appeared resigned to the extra costs. But Roger Berliner (D-Potomac-Bethesda), said he isn’t looking forward to the bill.

“I sort of feel like we’re watching RGIII’s ankle at this point,” Berliner said, referring to the recently injured quarterback for the Washington Redskins. “We’ll know more when the cast comes off.”

In early 2013, at Leggett’s request, the council approved $7.5 million to cover cost overruns, bringing the official cost of the project — originally priced at $93 million — to $12o million. About $70 million has come from state and federal contributions.

Leggett has said that Montgomery taxpayers will not be liable for any additional costs. But to complete the project without further delay, the county has decided to front the money and try to recover it by suing the contractors that it holds responsible for the problems — a process that could take years.

At Tuesday’s council briefing — the ninth on transit center matters since May 2013 — lawmakers once again pressed Dise to offer a timetable for completion of repairs. Dise said he is “optimistic” that the work can be finished by the end of the calendar year but would not commit to a date.

“The work has begun and will be continuous until completed,” he said. While cold weather or rain could slow application of the new concrete, he added, it will not hinder work on the strut beams.

The earliest and more modest version of the transit center , back in 1993, carried an estimated cost of $26 million. But as the project’s scope and design grew more ambitious — and delays and inflation took their toll — the price ticked steadily upward: $48 million in 1999, $75 million by 2006 and $93 million when ground was broken in 2008.

Construction was slowed by relocation of utility lines and unexpected environmental issues.

The council also received a briefing Tuesday from Inspector General Edward Blansitt, whose office released a report in May on what went wrong with the project. The report cites lax oversight of concrete quality by contractors, pouring and hardening of concrete in winter temperatures below established limits and design drawings that omitted key structural supports.

Blansitt said tighter managerial oversight and peer review of designs for big construction projects might have averted later trouble. County officials say they have already adopted some of his recommendations.