Concrete not strong enough to sustain the daily strain on the transit center is one of multiple design and construction failures identified by engineering consultants last week in a report on the $112 million train-and-bus hub, which is $80 million over budget and two years behind schedule. It was found to be unsafe and in need of significant repairs because of cracking and a lack of supporting steel in key locations.
Balter, an Owings Mill, Md., firm, handles field inspections and materials testing on all of the county’s capital construction projects, including the Silver Spring Civic Building, the Mid-County Community Recreation Center and the Grosvenor-Strathmore Metro garage. All were completed without questions about the firm’s work, according to county officials.
At the transit center, one of Balter’s key responsibilities was to test concrete as it was trucked to the construction site in 2010 and 2011. According to the study, by KCE Structural Engineers, the samples tested by Balter showed that the concrete met the required strength. But when the consultant tested samples taken from the finished slabs of roadway late last year, the concrete was found to be below the strength required by designers.
The report said the quality of the concrete was a factor in the facility’s excessive cracking. As built, the transit center has a useful life of about 12 years rather than the 50 years specified by the county’s contract with the builders, consultants said.
Balter, which was paid nearly $1 million for its work on the transit center, is not the only contractor called to account for deficiencies. The report cited the engineering firm Parsons Brinckerhoff for flaws in the building’s complex design, an ellipse-shaped structure of concrete beams, girders and slabs reinforced by a network of steel tendons and cables that were “stressed,” or wound too tightly, contributing to the cracking. The general contractor, Foulger-Pratt, did not follow contract documents and neglected to install critical supporting cables in concrete roadway slabs, the report said. Their absence would have created a safety hazard if not discovered.
Both of those companies have declined to comment on the study’s findings.
KCE concluded that Balter, as the field inspection firm, “did not raise sufficient concern regarding numerous issues that were known and/or became visible in the concrete during construction, apparently did not follow up on solutions to those issues, and did not perform their services in accordance with Industry Standard.”