The Teamsters union's three-vote election victory among the District's 2,300 Corrections Department employes is being challenged on the grounds that the city improperly let some supervisors vote and turned away others whose ballots could have changed the outcome, union and city officials said yesterday.

Teamsters Local 246 was declared the winner by an arbitrator two days after the hotly contested March 19 runoff election with the American Federation of Government Employees.

The final vote tally was 764 to 761, according to Arnold Ordman of the American Arbitration Association.

But AFGE this week filed an appeal with the D.C. Public Employee Relations Board, which has set an April 16 hearing for the case. PERB, which supervises city government employe relations, has postponed certifying the Teamsters as official bargaining agent for the Corrections Department pending outcome of the hearing, board chairman Addis Taylor said yesterday.

Ernie V. Jumalon, secretary-treasurer of the Teamsters local based in Northeast, called on the city to reject AFGE's appeal and begin negotiations with the city. He said AFGE is making a "futile attempt" to again raise arguments which Ordman rejected in the AAA-supervised ballot count.

Bernard Demczuk, AFGE's chief local organizer, said the appeal is based on the city's "erroneously" including on its master voting list more than 20 supervisors and teachers working under federal grants.

Supervisors are not union-eligible and the teachers, who work with inmates, were not bona fide city employes, he said.

AFGE officials believe as many as 40 ineligible people voted, and also contend that several off-duty employes of Lorton Reformatory were wrongly turned away when they attempted to cast their ballots at the D.C. Jail instead of at Lorton.

PERB customarily certifies election results based on the findings of impartial arbitrators conducting the vote.

But Taylor said this is apparently the first time in the board's five-year history that an election this close has been appealed by a losing union on procedural grounds. PERB could uphold the result, order a new election, "or try some more creative" resolution, Taylor said.

He declined to elaborate.

AFGE has represented the department's employes for 30 years, but growing dissatisfaction with low pay and dangerous working conditions prompted more than half the employes to petition PERB last year to join other unions.

A three-way vote last February between the two unions and the Fraternal Order of Police failed to generate a 50 percent tally for any union, forcing last month's runoff.