Faraday wrote that while some employees had received back pay payments of “over $20,000, others received only insignificant payments or nothing at all, even though they had longer periods of service and experienced similar working conditions.”

“A number of employees also told us that they were still being incorrectly classified, and/or were regularly required to perform duties outside their purported [Service Contract Act] classification,” he wrote.

In an interview, Faraday raised concerns that roughly half of those workers who were not interviewed by investigators had also participated in recent strikes. Faraday said he doubted the Labor Department would intentionally exclude those workers, but suggested management could have delayed interviews for certain workers.

[ Senate Food Workers Allege ‘Raise Theft’ ]

Faraday cited advice from the law firm Epstein Becker Green to employers that a Labor investigator “may not interfere with normal business operations.” Faraday said that hypothetically a manager could decline an interview if the worker is in the middle of a task.

Uddyback-Fortson said department investigators interview a “representative group of workers” — not every employee — to determine whether there has been an SCA violation.

“Once the violation has been established, the agency calculates back wages owed to all similarly situated employees,” Uddyback-Fortson wrote in an email. “A worker who feels that the back wages amount they received is not reflective of what they should be paid may provide additional evidence to the department.”

In the meantime, some workers are still in the dark about the back pay they received.

Alba Morales works as a cashier in the Dirksen Senate Office Building cafeteria. About a month ago, her manager called her into his office, and handed her a check for $238.

[ NLRB Finds Retaliation After Capitol Food Worker Strike ]

Morales was never interviewed by Labor investigators. She questioned whether the payment was correct, noting that she has been working for Restaurant Associates in the Senate for eight years. Her manager told her that the company gave investigators her employment information.

Morales pointed out that the information may not be correct, but her manager said he could not do anything about the payment since the payment decisions had been made.

“I’m still confused,” Morales said.

Morales has participated in several strikes where Senate workers have called for higher wages and union representation. Morales and Faraday both called for workers to be included in future discussions and allowed to consult with a third party.

“We see the moral of this story is … there needs to be an ongoing process for keeping workers collectively in the loop,” Faraday said.

Contact Bowman at bridgetbowman@rollcall.com and follow her on Twitter @bridgetbhc.