Another week, another letter from WMATA to Montgomery County expressing unhappiness over the Silver Spring Transit Center and efforts to repair design and construction problems.

The latest, delivered by courier on Friday, focuses on plans to fix two key 10-foot-by-40-foot roadway slabs at opposite ends of the center’s second level. The slabs were found to be without pre-tensioned steel supports that the county said were indicated in design drawings. WMATA, which is supposed to take over and operate the center when it is complete, has said it wants the slabs completely demolished and replaced.

But a working group of county officials and contractors agreed that complete demolition could damage other parts of the structure. They devised a plan to strengthen the slabs with pressure injections of concrete followed by a new protective overlay. In the July 19 letter, WMATA deputy general manager A. Robert Troup said that if the county proceeds, it is completely on the hook for any subsequent maintenance costs.

“If resolution cannot be achieved, then the county is considered to be on its own, and is responsible for directing the remediation effort as it deems appropriate,” Troup wrote, adding that the county “must commit to fixing future structural issues and perform requisite maintenance.”

Maintenance costs are a major issue between Montgomery County and WMATA. The transit agency was expected to handle maintenance as part of its operating duties. But the deficiencies in construction and design, including numerous cracks in beams and columns, and insufficient concrete cover in some areas, could make the facility more expensive to maintain. WMATA contends that it should not have to carry those costs on its own.

Troup also said that the county was moving with undue haste in its approach to repairs, and that the decision not to completely replace the slabs was “premature.”

County officials said it was WMATA that initially raised concerns about complete demolition. On Monday County Executive Isiah Leggett’s office produced an April 8 e-mail from the agency raising questions about complete replacement causing “further unanticipated stress to the structure.”

“We changed our approach because WMATA wanted us to,” said Leggett spokesman Patrick Lacefield.

County officials also said that WMATA never responded to its current repair plans within the prescribed 15-day window. Under the terms of their memorandum of understanding (MOU), WMATA gets 15 days to review and comment on changes in design proposed by the county. After that, the changes are deemed approved.

WMATA says that’s nonsense, and that its interest in complete slab removal has been a matter of record of many weeks. The transit agency is expected to present a detailed response to the slab issue Monday. The County Council is scheduled to discuss the matter Tuesday.