Jefferson W. Lewis, a 31-year veteran of the District of Columbia Fire Department, was chosen by Mayor Walter E. Washington yesterday to become the next city fire chief, despite opposition from the two major organizations representating the city's rank-and-file firefighters.

"He has demonstrated his ability to do what I think most citizens want and that is to put out a fire when they're in trouble," the mayor said in a press conference.

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The mayor's announcement capped more than four months of speculation and political maneuvering that had gone in the department since it became publicly known late last year that Fire Chief Burton W. Johnson planned to retire.Johnson left the department March 1, after being granted [WORD ILLEGIBLE] disability pension. [WORD ILLEGIBLE] who for more than three [WORD ILLEGIBLE] the assistant chief in charge [WORD ILLEGIBLE] was considered the [WORD ILLEGIBLE] to Johnson. But he [WORD ILLEGIBLE] choice of the fire [WORD ILLEGIBLE]

The firefighters Association of the District of Columbia, the union that represents most of the city's firefighters, said Lewis lacked the necessary administrative skills to run the 1,450-member department.

The Progressive Firefighters Association, a group representating most of the blacks in the department, did not question the administrative ability of Lewis, who is a black but not a member of that group.

But the Progressive Firefighters would have preferred someone who had been more actively involved with the concerns of the estimated 400 black firefighters in the department, according to the association spokesman, Lt. Rayfield Alfred.

In addition, some concern had been expressed in recent years that the heads of both public safety departments in the city should not be of the same race. Police Chief Burtell Jefferson is black.

The mayor said yesterday that he considered the racial factors, the views of the firefighters' groups and other factors before making an announcement. But he said, "I have not heard . . . anyone who has questioned his (Lewis') ability to fight fires and plan for the safety of this city."

David Ryan, president of the firefighters Association union, said that his organization would be "less than enthusiastic" about the choice of Lewis. "I think there will be problems with morale, a lot of it depending on what happens in the first part of Chief Lewis' administration."

Both Ryan and Alfred said, however, that internal problems could be overcome. "We were not in favor of him becoming the fire chief, but the fact is that he is the fire chief and we are professionals," Ryan said.

Lewis, who spoke briefly at the news conference after being hastily summoned to the mayor's office, agreed with Ryan's optimism. "As long as everyone does their job, I will try to do mine. I think those things will subside," he said. "I may be short talking, but I'll be fair with everyone."

Lewis, 58, joined the fire department in 1947 and was first assigned to the old Engine No. 27 company on Minnesota Avenue. Ten years later, he was promoted to sergeant and became a lieutenant in 1961. In 1965, he was promoted to captain and in 1970, he became one of the first black battalion chiefs in the department's history.

Since 1974, he has been assistant chief for operations, a job that put him in charge of the firefighting, ambulance, training and fire prevention units of the department. On 130 occasions during the past year, when Johnson was absent from work, Lewis served as acting head of the department.

His two principal rivals for the job were assistant chief John T. Devine, who is in charge of fire department administration, and John P. Breen, a battalion chief who until recently had been the city's fire marshal. Both were among several candidates supported by the firefighters union. Both are white.

The black group favored two other battalion chiefs, Alfred said. They were Joseph Kitt, and Jessie L. Cropps. Both are black.

Of the three major persons in contention, Lewis was the only one who is a city resident - a factor that is sometimes considered by the mayor in the appointment of city department heads.

Sam Eastman, the mayor's press secretary, said that less than two hours before the announcement was made at a press conference on a new housing program in the city, the mayor had conducted a final interview with Lewis in the mayor's office. At that time, Eastman said, the mayor told the soon-to-be chief that all of his questions about Lewis' qualifications had been satisfied, but the mayor did not tell Lewis he would be the chief.

Minutes before the press conference was to begin at 1:30 p.m., Eastman said, the mayor ordered Lewis to be telephoned and told to return to the District building. So unexpected was the mayor's announcement that it was accompanied by no prepared statement, and representatives of three major city news organizations were absent.

Asked why he made the announcement at that time, the mayor responded, "Because you're all here and I've completed our review." No date for Lewis swearing in was announced yesterday.

Lewis said that he planned no major changes in the department "in the near future," and would make "every efort to insure that the citizens of this town will have the best fire protection possible as they have had over the years."

Later he told an interviewer on WJLA-TV that he did not believe it was important that both he and Police Chief Jefferson are black. "For 100 years both of them (the public safety chiefs) were white and nobody had any problem," Lewis said.

Johnson's retirement, along with that of former police chief maurice J. Cullinane, assistant police chief Tilmon O'Bryant and others have focused attention in recent months on the city's police and firemen's pension system, which some critics felt is too generous.

When asked about the system and possible abuses of it at yesterday's news conference, Lewis said he hd no comment.

"You don't have any opinion on it?" a reporter asked.

"Not really," Lewis responded. "I'm not thinking about retiring."