The Alexandria City Council voted 7-0 on Saturday to revoke the operating status of the Mirant power plant, an aging coal-fired facility on the Potomac River in the north end of town.

The power plant, which supplies power to residents in the District and Maryland but not Virginia, has long been a thorn in the side of city officials, who agree with residents' contentions that it emits unhealthy levels of noxious gases and particulate matter. The plant recently reached an agreement with state and federal officials that will allow it to continue to operate while reducing dramatically the amount of nitrous oxide it emits.

The city's move means that the power plant will eventually have to reapply for a special operating permit and modernize or close down, according to City Attorney Ignacio B. Pessoa. But Mayor William D. Euille (D) noted that despite the council's action, the matter could take years of negotiation and potential litigation to resolve.

Lee Davis, vice president for Mirant Mid-Atlantic, had told the council that the plant is an important part of the region's power grid and that company officials have taken steps in recent months to address the concerns about unhealthy emissions.