The numbers have begun to add up fast in the past year for Local 400 of the United Food and Commercial Workers International Union.

Last June the union won the right to represent nearly 6,000 workers at Woodward & Lothrop department stores. In May it absorbed approximately 5,000 meatcutters through a merger with that local union. And in September the former retail clerks union will probably add another 600 members through a merger with the barbers.

What this all adds up to is more than 25,000 members. That makes Local 400 easily the biggest union in the Washington area.

The figures also add up to something that may have even more impact in the future -- a large aggressive labor organization in an area not famous for its unions.

With massive aid from the international union organization, the local organized Woodies in a drive that left little doubt about its intentions for other Washington area retailers. "They didn't spend the kind of money they spent just for us," Woodies President Edwin K. Hofman said at the time. Hecht's and Garfinckel's would appear to be next in line.

In a quieter action last month, the union organized Hemisphere National Bank, a move that the president of the local union views as the beginning of a drive to organize area banks.

Organizers are busy in area hair cutting chains, credit unions, optical centers and on the fringes of the large drug chains, hospitals and nursing homes -- laying the groundwork for additional campaigns that could swell the union's ranks and give the area a more organized work force. The union is strongest in food stores -- such as Giant, Safeway, A&P and the other major chains -- where they represent the clerks and now the meatcutters as well.

"I'm as optimistic as I can be in the service trades area. Just about any area we want to move into, the response is terrific," said Thomas McNutt, president of Local 400 since 1975. Under McNutt's administration, the union has become a large, highly visible organization.

"I think this area is a lot more receptive to organization than it once was," said McNutt. Hard times and the low salaries of the workers that Local 400 organizes have helped add to the union's appeal, he said. Many of the workers the union hopes to organize, including clerks in major department stores, make only the minimum wage, compared with a grocery clerk, who makes $8.73 an hour and receives free dental and optical care.

Although McNutt's dozen organizers have plenty of targets in mind, it is unlikely that the union local will launch another major organizing drive in the near future. First the union must negotiate a new contract for area grocery workers. Formal contract renewal talks begin July 18.

McNutt is a former steelworker with a high school education, who joined the union when he went to work for an A&P food store in Detroit. McNutt took the job in the grocery after he was laid off from the steel mill. m

Orifinally recruited as a shop steward, in 1961 he went to work in organizing for the international union, then called the Retail Clerks but since merged with the Amalgamated MeatCutters to become the United Food and Commercial Workers International Union. In 1974, he moved to the union's headquarters in Washington where he was working when the international union needed someone to step in and take control of the Washington area local. u

"He substantially turned it around," said Jay Foreman, an international vice president of the United Food and Commercial Workers. "He's tenacious as hell. He's willing to take a loss and pursue it till it's a victory."

The Washington area local is now one of the three largest United Food and Commercial Workers locals in the nation, said Foreman.

Six months ago the local union moved into its own building, a $4.5 million office building near the Beltway Amtrak and Metro stops in Prince George's County. Within the building are an optical clinic and a dental clinic with seven dentists where local members can come for the free services that have been negotiated for them. The building also houses the lawyers who provide service for members. A van that travels to food stores to give free physicals to members is parked outiside the building.

McNutt gets high marks from other area labor officials and from some management officials. "I think it's fair to say that Giant has a very good working relationship with Local 400," said Eric Weiss, assistant to the vice president for labor relations at Giant. "I think they're a very professional organization, and I think a great deal of Tom McNutt," he said.

"It's a very, very, very aggressive union. He's a smart individual," said Joslyn Williams, executive assistant to the president of the Greater Washington Central Labor Council.

The growth of Local 400 has been art of a broader change in the area's labor movement. Once dominated by the building trades unions, whose image has been conservative and exclusionary, the area labor movement is increasingly dominated by unions in service industries and by public groups.

Labor also shows some glimmer of becoming an effective poltical force in this area. McNutt said he is organizing groups of Local 400 workers in every congressional district where his members live. The local union represents workers in Maryland, the District and Virginia, where its jurisdiction stretches almost to Richmond.

Not everything has gone without hitches for Local 400. An organizing drive at Trak auto supply stores, a Dart Drug subsidiary, was temporarily halted when four workers who signed cards supporting representation were fired. hRecently, though, the company agreed to pay the workers back pay for the period since they were fired. McNutt said that the union will continue its efforts to organize.

Local 400 also took on a costly strike at Raleigh's that finally was settled successfully after 27 days. The strike, over a new contract, cost the union approximately $13,000 a week in benefits. Union pickets kept most shoppers out of the store, and McNutt claims the strike even helped the union, which already represented Raleigh's, organize other stores.