The Arlington Country Board defeated last night a controversial proposal by Metro to construct a bus garage ane employe parking lot on land near the site of the Ballston subway station, scheduled to open next year.

The proposal, first made to the Metro Board in 1974 by Arlington Board member Joseph S. Wholey, was opposed by the country planning commission, about 60 areas residents who attended last night's meeting and officials of the Chessie System Inc., which owns the vacant 13-acre tract and plans to build a shopping center on the site.

The new garage, which would have housed 233 buses would have replaced a smaller existing bus garage located on North Quincy Street near the Parkington Shopping Center. Construction of the new garage by Metro was contingent upon approval by Arlington officials.

"We would have 233 diesel engines in there, said Karin Sheldon one of several residents who testified against the proposal. "The citizens would have to put up with noise, traffic and health hazards."

Chessie attorney H. Thomas Dunck told the board that a shopping center would produce about $350,000 in annual real estate taxes. "This site has always been regarded as one of our most valuable," Dunck told the board.

Wholey, who also is Metro board chairman, unsuccessfully urged his colleagues to approve the new garage as a buffer against the type of highrise development in Rosslyn.

"There will be very high density development on this sith unless it is blocked by something else," said Wholey, who cast the lone vote supporting of the proposal.

Metro officials said last night that the vote means the Metro board must consider constructing a new garage in a neighboring jurisdiction.