Metro General Manager Paul J. Wiedefeld. (Matt McClain/The Washington Post)

Prince George’s County has emerged as an additional hurdle to Metro General Manager Paul J. Wiedefeld’s long-term funding plan for the system, as concerns rise about its potential impact on the workforce in a county where a significant number of Metro workers reside.

The biggest opposition to the proposal for $500 million in annual dedicated funding was expected to come from Northern Virginia, but on Thursday, Metro board member Malcolm Augustine, who represents Prince George’s, cast the lone dissenting vote in “Sense of the [Metro] Board” resolution designed to gauge where the region stands on Wiedefeld’s plan.

The proposal calls for $15.5 billion over 10 years to keep the system “safe and reliable,” $500 million in permanent annual dedicated funding from the region, and a slew of labor concessions.

The measure passed by a 14-to-1 vote — with one board member absent. Augustine had signaled his wariness of the proposal in an interview Wednesday. A “yes” vote indicated that a board member “endorses the framework and principles” in the plan.

Wiedefeld’s plan, Augustine told the board, should be geared toward providing safe and reliable service and winning back riders, regaining trust and spurring growth in the D.C. region.

“To achieve this mission, [Metro] must recognize and nurture its greatest asset — the employees who move 300 million people each year — that has to be emphasized,” Augustine said. “In addition to identifying the broad conditions in his plan which we can all can agree on to a certain degree, Mr. Wiedefeld mapped some specific actions — some of which I will not support — to achieve the goal of long-term health.”

He said Wiedefeld’s proposal should be subjected to further scrutiny before the board takes a position.

“The board should and will participate in this process,” Augustine said, “but any endorsement prior to our own deliberation in my opinion would be premature and for those reasons I will not be supporting this.”

One of Augustine’s key concerns is Wiedefeld’s call for significant concessions from Metro’s unions. Prince George’s is home to 44 percent of Metro’s workforce.

Wiedefeld, for example, has said he would honor existing pension commitments to current employees and retirees, but wants to save money by providing 401(k) retirement plans — which are less expensive — for new hires.

He also wants to cut costs by opening to competition positions that Metro can outsource, such as station managers and track inspectors on phase II of the Silver Line, slated to open in 2020.

There “were some very specific recommendations in there when you start talking about changing the Wolf Act, when you start talking about privatizing functions — those are very specific,” Augustine said Wednesday, referring to the 1995 federal law that governs arbitration of labor disputes. “You have the visionary goals, which of course we can agree and share with, but on the other hand you went down into the weeds a little bit — so that requires some scrutiny that requires some discussion that, to me, is part of the contemplation that we’re doing.”

And he declined to commit to the idea that Metro needs $500 million in annual dedicated funding, as Wiedefeld proposes, before clarifying Thursday that he agrees with the need for a “long-term financial commitment from the funding jurisdictions.”

Other board members universally expressed their support for the plan, while agreeing there are aspects that need more analysis. The framework of the proposal was endorsed last week by the Northern Virginia Transportation Commission. The Metropolitan Washington Council of Governments also supports dedicated funding and in an analysis recommended Metro receive $650 million a year to cover capital and maintenance costs.

“I welcome advice, but it’s the general manager that is going to run this agency and I am willing to support where he is today,” said Board member Cathy Hudgins, who represents Fairfax County. “I also have very much clarity in my mind that that voice of mine is not closed once I vote yes to this.”

Maryland board members Michael Goldman, Keturah Harley and Kathy Porter also backed the proposal, with Porter summing it up this way: “I don’t want us to lose sight of the forest for the trees.”

Metro, the nation’s second-busiest subway, stands alone among large subway systems in lacking dedicated funding, which impedes the transit system’s long-term borrowing abilities.

Augustine said Wednesday that the state “already has” dedicated funding in the form of the Maryland Transportation Trust Fund and “we have yet to see a year or a time when the state of Maryland has not contributed the jurisdictional subsidy to [Metro] in history.”

Augustine’s position of relying on the state appears to contradict that of Maryland Gov. Larry Hogan (R), who has said that the state will not raise taxes to pay for Metro. Hogan, however, has said that if Prince George’s and Montgomery counties — which are served by Metro — want to tax themselves to support the transit system, they can do so.

The proposal being floated is a 1-cent regionwide sales tax, which one study says would raise $650 million annually — enough to keep the system safe and reliable, plus extra money to pay for some expansion.

In a statement Thursday, Prince George’s County Executive Rushern L. Baker III (D) echoed Augustine’s position, emphasizing the need to support Metro employees.

“In addition to identifying the broad conditions in his plan, Mr. Wiedefeld attempted to outline specific actions to achieve the goal of long-term health,” Baker said. “These proposals deserve consideration but require additional study and consultation, within the context provided above, with regard to their impact and overall viability towards achieving our goal of a safe, reliable, affordable and efficient Metro.”

A recent Washington Post-University of Maryland poll found that Marylanders narrowly support a regionwide sales tax for Metro. The tax was backed by 55 percent of Montgomery County residents, compared with 44 percent in Prince George’s — differences that fell within the poll’s margin of error. Prince George’s voters have consistently resisted raising taxes.

It had been expected that the most vocal opposition for the proposal would come from Northern Virginia. Virginia officials are sharply divided over a uniform regional sales tax because Northern Virginia would contribute an estimated 51 percent of the $650 million raised annually — even though it pays less than either Maryland or the District under Metro’s standard funding formula.

Loudoun County Supervisor Matthew F. Letourneau (R-Dulles) said the proposal is a nonstarter, and told constituents in a monthly newsletter the chances of such a measure passing in the Virginia General Assembly and then among individual localities is “virtually zero.”

He emphasized that the plan is unlikely to move without Virginia’s support.

“The general consensus has always been that Virginia is going to be the toughest nut to crack,” Letourneau said.

Wiedefeld said Thursday he has “the same concerns for employees” as Augustine, but the agency needs to tackle the issues in front of it. Minutes before the vote, he urged the board to back the concept and laid out a vision of what might happen if no action is taken.

“What we’re talking about is transformative in nature, it’s large to do, it’s not gonna be easy by any means, but I think the alternative is pretty clear,” he said. “We further decline. We further chase riders away. … That will impact, I believe, the economic well-being of this region.”

Robert McCartney contributed to this report.