Challenges to furloughs could swamp the agency that hears appeals of personnel actions affecting federal employees, although legal experts warn that workers bringing such cases would face long odds.

More than 1 million federal employees face the possibility of being furloughed if automatic spending cuts — known as sequestration — kick in Friday. That is what will happen if lawmakers fail to agree on a deficit-reduction plan by then.

“It actually hits us three times,” Susan Tsui Grundmann, chair of the Merit Systems Protection Board, said in an interview this week. “First, there’s going to be an impact on the workload. Second, we might have to furlough our own employees. Third, if our own employees choose to appeal their furloughs, those appeals could not be heard here. We would have to pay for that to be heard outside. It’s really the perfect storm for us.”

The number of furlough days would vary among agencies, as would the timing. Workers must receive 30 days’ notice, meaning furloughs could not start before April.

Employees are entitled to respond to the furlough notice, review agency documentation and receive an agency reply. In addition, for up to 30 days after the first actual unpaid leave day, employees may file an appeal with the MSPB, a quasi-judicial agency with regional hearing officials and a three-member appeals board.

Grundmann sent a letter to Congress last week warning of the potential impact.

During fiscal 2012, the MSPB issued about 7,600 decisions. If more than 1 million employees were furloughed and just 1 percent of them filed appeals, “that would be about double what we usually process,” she said.

“We still are going to be hearing cases on veterans’ claims. We’re still going to be hearing whistleblower cases, appeals of retirement decisions,” she added.

Grundmann said it took the MSPB several years to process its last big surge of cases, about 12,000 appeals from air traffic controllers fired for striking in 1981. Even if Congress provided money to hire more hearing officers, as happened then, the agency would face a major challenge because of the time it would take to train them, she said.

Employees who file appeals will find that their rights are limited, said several lawyers who practice in the field. An appeal would not prevent an employee from being furloughed, and those who ultimately prevailed would receive only back pay, attorney’s fees and, in some cases, compensatory damages.

William L. Bransford, a lawyer with Shaw Bransford & Roth, said he thought that in most cases, furlough decisions would survive appeals. “MSPB would uphold the furlough unless the employee could prove what’s called an affirmative defense.”

Such grounds could include allegations of favoritism, discrimination or whistleblower retaliation. “If an employee could prove those things, they could win an appeal,” Bransford said. “But the burden of proof is on the employee. You have to show you’re being treated differently than other employees. If everyone is being treated the same, you’re not going to be able to show that.”

“If they furlough the whole office, how are you going to claim disparate treatment?” asked Edward H. Passman, a lawyer with Passman & Kaplan. “The ultimate determination of whether there’s furlough is at management’s discretion. All they have to prove is the efficiency of the service, which is a fairly easy burden for an agency to meet.”

In terms of precedent, furlough cases are “largely unexplored territory,” said Jessica Parks, a former MSPB vice chairman who is now with Kator, Parks & Weiser. She said that many earlier cases involved special rules applying to one small group of employees, administrative law judges.

In one leading case from 1984 not involving such employees, the MSPB upheld a furlough after ruling that it was “a reasonable management solution to the financial restrictions” on the agency. The MSBP said it would not interfere with management’s decision without a showing of “disparate treatment among similarly situated” employees.

“It comes down to: Are there going to be fairness issues? And that depends on how each agency handles it,” Parks said.

In addition to unequal treatment, an employee could allege an error in the required procedures. “While that may sound simple, we see in our practice that agencies often don’t follow procedures correctly,” Parks said. “Sometimes they make mistakes. If that happened in a particular case, it could result in the reversal of an action and then back pay and other relief.”

Bransford said: “This really is kind of an unprecedented time, and we don’t know whether federal employees are going to react by filing a lot of appeals or whether they’re going to feel it’s not worth their time and effort. Not that they can’t win, but it’s a real uphill battle.”