The problem-plagued Silver Spring Transit Center. (Katherine Frey/The Washington Post)

Montgomery County and Metro have filed a $166 million lawsuit against the companies that designed, built and inspected the Silver Spring Transit Center, contending that their “collective failure” led to five years of delays and $50 million in cost overruns to correct substandard work.

The long-anticipated, 62-page complaint, filed this week in Montgomery County Circuit Court, accuses designer Parsons Brinckerhoff, general contractor Foulger-Pratt, and construction inspection firm Robert B. Balter of multiple counts of negligence and breach of contract.

It alleges that Parsons Brincker­hoff did not design floors in the transit center that would be strong enough to handle the daily forces exerted by hundreds of buses dropping off and picking up passengers. It also accuses the firm, an internationally prominent engineering and design company, of intentionally misrepresenting what work it had done to calculate potential pressures on the building’s interior beams and girders.

In a statement issued late Friday, Parsons Brinckerhoff said: “The complaint is overblown and simply incorrect in its allegations. This lawsuit is wholly without merit and will be vigorously defended.”

The complaint charges that Foulger-Pratt failed to complete its work in a timely manner and properly oversee the work of the project’s various subcontractors. Balter is accused of failing to ensure that the concrete used for the building had the proper strength and was properly poured.

Overall, the county and Metro said, missteps by the three firms led to cracks and other defects in the three-story concrete structure, envisioned as a bus, taxi and bicycle hub next to the Silver Spring Metrorail station. The problems and subsequent infighting among the players delayed completion of the facility for years and turned the venture into a massive black eye for a county accustomed to smoothly delivering capital projects.

The $120 million center is scheduled to finally open to passenger service Sept. 20. Had the facility “been designed and constructed correctly,” the complaint says, it would have opened in September 2010.

“Despite their collective failure to provide the public what it has paid for [the three firms] each have received a substantial amount of public funds for their respective work” on the transit center, the complaint says.

According to the lawsuit, the county seeks no less than $50 million in damages from Parsons Brinckerhoff and ­Foulger-Pratt for failing to prevent construction defects or bringing them to the county’s attention. The suit seeks $30 million from Balter for failing in its inspection duties.

Metro, which will operate the transit center as part of its regional bus and train system, seeks no less than $25.8 from Parsons Brinckerhoff, Foulger-Pratt and Balter for additional monitoring, inspection, maintenance and repair costs it expects to incur because of defective design and construction.

The most provocative allegation in the complaint is that Parsons Brinckerhoff was “less than forthcoming” with the county over whether it had performed calculations to ensure that the transit center’s concrete could withstand torsion — a twisting force exerted when concrete is under pressure — and shearing — the vertical force that can cause concrete to crack or fail.

According to the complaint, the county asked Parsons Brinckerhoff to provide the shear and torsion calculations at a series of meetings beginning in 2013.

In response, county attorneys said, Parsons Brinckerhoff “stated falsely that it had already provided the data.”

The lawsuit says the company’s “intentional misrepresentations” delayed repairs to the interior beams and girders, “causing substantial additional delays.” The county is seeking $60 million in punitive damages from the firm.

Jerry Jannetti, vice president of Parsons Brinckerhoff, told The Washington Post last year that industry standards did not require that torsion and shearing be taken into account in a building such as the transit center.

The lawsuit is the first of what is expected to be a series of claims filed by major players involved in the transit center.

The county filed its action in circuit court Monday but has not announced it, County Attorney Marc Hansen said, because officials wanted to wait until they knew which docket the case would be assigned to.

The county wants to see the matter placed on the “business and technology” docket, because it would allow more time to prepare.

The suit is also notable in that it aligns the county and Metro as plaintiffs. The two have been at odds over most of the past five years over the project, which was built by the county but will be operated by the transit agency.

Until a couple of weeks ago, Metro was seeking millions of dollars directly from the county to pay for additional maintenance and repair costs. It now appears that the two have settled their differences.