The inspection and materials testing firm that worked on the Silver Spring Transit Center says a consultant’s report holding it partly responsible for construction flaws was based on “insufficient information, inappropriate speculation and a lack of understanding” of the firm’s role.

The Robert B. Balter Co. made its first public comments on the troubled $120 million Montgomery County project in a lengthy rebuttal posted Friday on the Web site of the county’s Department of General Services.

Balter had been cited in March by KCE Structural Engineers, consultants hired by the county, for failing to raise sufficient concerns about about cracks in concrete and the absence of supporting steel in some areas of the transit center. KCE concluded that Balter, along with Parsons Brinckerhoff, the designer, and Foulger-Pratt, the general contractor, did not perform according to industry standards.

In the rebuttal, company President Lori A. Balter said her Owings Mill firm, which has handled inspections of major county projects without apparent incident for the past several years, did raise concerns about construction deficiencies when appropriate.

She added that Balter’s services, for which it was paid about $1 million, “were performed under the continuous scrutiny of, and in coordination with representatives from Montgomery County and WMATA,” the Washington Metropolitan Area Transit Authority.

Concrete issues at the Silver Spring Transit Center

Balter’s 17-page response, with hundreds of pages of documents attached, sheds little new light on why the three-level concrete train and bus hub remains unusable and in need of major repairs after two years of delays and tens of millions of dollars in cost overruns. The firm admits to no errors and holds the other contractors responsible for deficiencies identified by KCE.

It challenges the impartiality of KCE, which assigned blame to all major parties participating in the project except the county, which hired it.

KCE reported that concrete it tested from the completed building was weaker than samples evaluated by Balter during construction. Testing of concrete was one of the firm’s main responsibilities. Balter said it was “misleading” to directly compare the two sets of samples because extensive handling and long-distance shipping caused microcracks in the concrete that KCE tested from the finished structure.

Balter also rebutted KCE’s assertion that not all of Balter’s personnel were certified to work with high-strength concrete, and supplied a long list of credentials for its transit center team. Instead, it accused KCE of hiring firms that were not properly accredited to test concrete.

According to KCE, Balter noted identical water-to-cement ratios on all of its concrete samples, raising the possibility that these were “default” values inserted by Balter without actual testing.

Balter said it was only reporting information provided by the concrete supplier, Rockville Fuel and Feed.

Balter addresses one of the most critical items flagged by KCE, the absence of supporting steel in two 760-square-foot strips of roadway on the east and west ends of the center’s second level. Pouring concrete into the strips without the steel left the roadway weakened and a potential safety hazard, KCE said.

Balter said it worked from what are known as shop drawings that did not call for placement of steel in the strips. “Those drawings were approved by Parsons Brinckerhoff,” Balter said, “and presumably contained all engineering comments and requirements.”

County officials have said that the drawings, which were created by a subcontractor, were never submitted to Parsons Brinckerhoff for approval.

Balter also accuses KCE of casting doubt on its diligence by referring to a lack of documentation for routine matters. KCE, for example, said Balter provided no reports documenting whether “post-tensioning” — strengthening of concrete slabs with steel bars known as tendons — was done within 96 hours of the concrete being poured, as required.

Balter said its job was to report when contractors failed to follow procedures, not when they complied.

“Balter was not required to document every instance when the contractor properly performed work,” the rebuttal said.

Spokesmen for Montgomery County, Foulger-Pratt and Balter did not respond to phone and e-mail requests for comment Friday. A spokesman for Parsons Brinckerhoff declined to comment. KCE President Allyn E. Kilsheimer also declined to comment because he hadn’t read Balter’s rebuttal and because the county had not authorized him to speak publicly about the project.