A proposal by Metro officials to build a maintenance garage for Metrobuses in Southwest Washington was supported last night by District officials, but opposed by community residents and business owners.

The transit authority has recommended a site at First and Q streets SW for a new garage for about 250 buses serving routes in Southeast and Southwest. The structure, expected to cost $25 million to $35 million, would replace a Metrobus garage at M and Half streets SE that is considered obsolete.

At a hearing last night, Sherri Y. Alston, the District's mass transit chief, endorsed the proposal. She described the existing facility as "the worst garage in the Metro system," and added, "We have debated this issue for more than a decade and it is time to act."

William D. Reeves, an Advisory Neighborhood Commission chairman, criticized the plan, arguing that it would lead to increased noise, air pollution and traffic congestion, and would jeopardize small businesses and development projects.

The proposal also was opposed by an official of the Potomac Electric Power Co., which owns part of the proposed site. Several business owners argued that the plan would disrupt local businesses and that a cheaper site is available nearby. A spokesman for Fort McNair said officials do not oppose the plan.