Pepco employee, James Tarantella climbs out of a bucket after fixing a blown fuse on a power outage call on Monday August 13, 2012 in Rockville, Md. (Matt McClain/FOR THE WASHINGTON POST)

A new contract between Pepco and its 1,150 linemen, electricians and other workers has stalled for months, and union leaders said they’re worried that the first strike in 27 years could soon happen.

Despite 51 meetings and help from a federal mediator, the company and its union, International Brotherhood of Electrical Workers Local 1900, are at an impasse. Last week, Pepco offered what it describes as its “last, best and final” offer to union leaders, who will brief members on the details Monday.

On Wednesday, members are scheduled to vote on the offer. Union leadership wants them to reject it. If that happens, the union could strike, or Pepco could declare a lockout. A work stoppage would be the second in the company’s 116-year history and the first since August 1985.

IBEW Local 1900 President James A. Griffin said he was not confident that a strike or a lockout can be avoided. “The only other time I felt like this was in 1985,” he said.

A strike would come at a bad time for Pepco, which serves 788,000 customers in Maryland and the District and has been criticized in recent years over its response to power outages. Employees and local officials have also faulted Pepco for employing too few senior linemen and too many less-capable contractors to fix utility equipment.

Pepco spokeswoman Myra Oppel said that a lockout “is not something we are considering.” She added that the offer is “fair and reasonable by any standard, especially in these difficult economic times.”

In 1985, the union’s 3,300 members walked out for five days after contract negotiations fell apart. At issue was the company’s resistance to giving more generous pay and benefits despite earning record profits at the time: $168 million in 1984. Workers picketed the 10 Pepco facilities for days.

Before the strike, Pepco had offered the workers raises of 13 percent over three years but increased deductibles for medical coverage to $325 from $150. Pepco and union leaders eventually agreed to a contract that offered increases of 18 to 30 percent over three years and pushed back the deductible increase by two years.

During the strike, Pepco had 1,800 management employees serve as replacement workers. Griffin said Pepco had problems handling outages at the time. In an e-mail to Montgomery County officials last week, a Pepco executive, Jerry Pasternak, said the company doesn’t want a strike but has trained “hundreds” of management employees in case it happens.

Oppel said the company also has more than 400 contractors ready to help in case a serious weather event occurs. It is unlikely that contractors will be summoned, as the weather this week is expected to be more or less tranquil.

To avoid a work stoppage, Pepco and union officials have extended the current contract, which was set to expire in May, at least four times, Griffin said. Although the extension ended last week, the contract is still in effect until one side says it wants the work stoppage, and that wouldn’t happen until after Wednesday’s vote.

Union officials have distributed a 24-page document detailing the offer to union members. “There is no question in our minds that this offer you will vote on is the worst proposal this Local has faced in its entire history,” the union negotiators wrote in the document.

The union’s largest concern is a change to its health and welfare plans. Pepco’s offer would eliminate the union’s ability to file grievances and go into arbitration concerning the plan. Instead, the union would have to follow a separate appeals process, which Griffin said is overly arduous. He added that the company could make arbitrary, potentially harmful changes in the future because of this change.

Oppel said that no changes would occur in 2013 and that the union has not arbitrated on health and welfare issues over the past 30 years.

Meanwhile, company officials said the offer provides workers many benefits. In his e-mail, Pasternak said experienced linemen would end up with a more than 13 percent raise over four years. The company also pledges to try to hire 220 more union employees within four years.

But Griffin said the pledge is not a guarantee, nor does it mean that 220 additional workers will be on the ground. If the company loses 220 current workers over the next four years, it could still fulfill its pledge without adding anyone. (Oppel said in response that, if needed, the company would try to hire more than 220 workers.)

“Our members . . . know what will happen if we allow them to do this to our health and welfare plans,” Griffin said. “When you take into consideration what they have proposed for the health and welfare plans, there is not enough money they can offer us to make up for that.”

The Maryland Public Service Commission is “closely” watching the contract negotiations, spokeswoman Regina L. Davis said. She declined to comment further.

Montgomery County Council President Roger Berliner (D-Potomac-Bethesda), who has been critical of Pepco, said he hopes the negotiations wrap up quickly. “We all hope that this can get resolved in a way that is satisfactory and so that we have the linemen that we need,” he said.

Capital Weather Gang editor Jason Samenow contributed to this report.