One year after Metro fired 16 track workers for allegedly falsifying inspection reports, their cases have gone to binding arbitration, and Metro's largest union is suing the transit agency — accusing it of stalling the arbitration process.

In the lawsuit, filed Wednesday in U.S. District Court in Virginia, attorneys for the Amalgamated Transit Union Local 689 said Metro is demonstrating a "refusal to participate in the arbitration proceedings."

The union wants the court to instruct arbitrators to consider all 16 cases as one "group grievance" — the equivalent of a class-action lawsuit. But Metro's lawyers argue that the arbitration board does not have the power to require that the 16 disparate cases be considered as one entity.

And though the lawsuit centers on a technical question within the arbitration process, it's the first public acknowledgment that the high-profile case of the fired track inspectors has reached binding arbitration, a common practice in disagreements between Metro and union officials that has served as a political flash point in recent years.

Some politicians have argued that arbitrators usually side with the union, amping up the costs to taxpayers or offering second chances to poorly performing workers. Others would support more long-term funding to Metro if binding arbitration is eliminated, though a recent funding bill floated by Rep. Barbara Comstock (R-Va.) stops short of that requirement.

Still, if the terminated track inspectors are rehired by Metro, it could bring more scrutiny to the agency and its embattled union.

Metro spokesman Dan Stessel declined to comment on the lawsuit.

The 16 track inspectors at issue were terminated after an investigation into the July 2016 derailment at East Falls Church station, which resulted in several minor injuries and more than $1 million in damage to the tracks and train.

The derailment was caused by a train that skidded off the rails because the tracks had spread too wide, a defective condition that usually happens after years of inattention and postponed repairs.

Metro has accused the 16 track inspectors of fabricating measurements on track inspection reports in the months before the derailment. Managers also fired five supervisors, who are not represented by ATU Local 689. In total, one-third of Metro's track inspection department was terminated, and others were disciplined.

But union representatives point out that Metro has provided no proof that the workers who were fired had maintained the section of track where the derailment occurred.

They also argue that workers did not receive adequate training.

In the lawsuit filed last week, the union's lawyers assert that Metro's track inspection program was designed to keep the trains running, not to shut down stretches of track for safety maintenance.

" . . . WMATA is scapegoating these workers for insufficient track inspection which was intentionally designed by WMATA so as to avoid speed restrictions and immediate repair costs," read court documents filed by the workers. "The culture and practice in track inspection has been to file routine reports and to discourage reporting problems which might disrupt rail operation."

The lawsuit also included an account from one terminated track inspector, John Evans, who wrote that he was never properly trained on that protocol for track inspections.

"Only had 1 day of training on how to perform switch inspection and had to learn procedures in the field on my own or from senior track personnel," Evans wrote in his grievance document.

He also said he did not have access to Metro's digital database of track inspection reports, suggesting that he would not have been able to copy-and-paste the measurements from previous months.

"WMATA never showed proof of accurate measurement that would prove my work inaccurate or . . . that my documents were falsified," the track worker wrote.

The union's lawyers also argue that the terminations were illegitimate, because the employees were fired more than six months after the date of their alleged wrongdoings — exceeding the statue of limitations laid out in Metro's contract with the union.