WASHINGTON — The Merit Systems Protection Board, a quasi-judicial government body tasked with settling workplace disputes for millions of federal workers, is officially vacant for the first time in its 40-year history.

The board became empty at midnight Thursday, after the Senate failed to act on a measure to extend the term of the board's sole remaining member and acting chairman, Mark Robbins. The House approved the extension Monday.

The three-member board needs at least two members to decide appeals from civil servants. All three members are presidentially appointed and Senate-confirmed for staggered seven-year terms, with no more than two affiliated with the same political party. After one member termed out in 2015 and a second did so in January 2017, both without replacements, Robbins became the board's sole member. His term expired at midnight on Feb. 28.

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President Donald Trump nominated two members to the board, including Robbins' replacement, after one year in office, and nominated a third months later. But the nominees were not approved by the Senate before the end of the last Congress. One of those nominees withdrew his name from consideration, and the other two are still under consideration.

Robbins has been by himself on the board for more than two years. He's diligently reviewed the nearly 2,000 cases that have come across his desk, but without a second member to cast a vote on a resolution, those cases have sat idle in a fast-growing backlog. With no members on the board, that backlog will keep growing.

Without a quorum, Robbins hasn't been able to fulfill other MSPB duties, including releasing studies on the civil service and conducting reviews of the rules and regulations at OPM, over which the MSPB has oversight.

Robbins on Thursday told a House Committee on Oversight and Reform subcommittee that he expects it would take three years to clear the backlog.

Experts offered testimony voicing concern for the future of the MSPB, and the workers who are waiting in limbo for their cases to be determined.

"In short, the impact of the extended vacancies has been devastating," said John Palguta, a former MSPB policy director. "The current situation has substantially undermined MSPB's ability to fulfill its statutory mandate to provide due process for federal employees and to protect the public interest in a civil service free of prohibited personnel practices, including actions taken for discriminatory or partisan political purposes."

Although a vacant board is unprecedented, it doesn't mean the agency will grind to a halt, Robbins said. The board's general counsel will become its acting executive and administrative officer. In the absence of board members, administrative judges will continue hearing cases and issuing initial decisions. If an employee decides to appeal, they would then need to go directly to a federal court.