Mirant Corp. plans to propose that its Alexandria power plant, which provides electricity to homes in the District and Maryland, be allowed to reopen on a limited basis. The plant was closed last month because of environmental problems.

Under a tentative plan Mirant outlined last week in documents filed with federal regulators, the Potomac River plant would operate at a level "significantly reduced from full capacity" that does not violate national air quality standards. At the same time, Mirant would continue studying long-term fixes such as burning cleaner coal or raising the height of the plant's smokestacks to disperse pollutants.

The plan must pass muster with the Virginia Department of Environmental Quality (DEQ), which has ordered Mirant to take immediate steps to reduce pollution. DEQ spokesman Bill Hayden said the department has not seen a proposal from Mirant but "will take a look at what they do propose. The main thing we're looking for is, if they are continuing to operate, it must be in a way that does not violate air quality standards.''

Federal regulators, meanwhile, are also evaluating a petition, filed by the D.C. Public Service Commission, that asks them to order the plant to reopen. Mirant revealed that it will probably propose the partial reopening in documents the company filed last week with the Federal Energy Regulatory Commission.

Amid the blitz of regulatory activity, it remains unclear when the plant might reopen, even temporarily. And Mirant acknowledges that a full-scale resumption of operations could be more than a year away. Although the plant is in Alexandria, it does not serve Virginia.

Mirant decided Aug. 24 to shut down the plant in response to the order from Virginia officials to cut potentially harmful pollution from the coal-fired facility. The directive by the Department of Environmental Quality came after it reviewed the results of an analysis that showed some pollutants found in the plant's vicinity are at times considerably higher than what national standards allow.

Neighbors of Mirant have complained for years about what they believe to be high levels of contaminants emanating from the plant.

But the 56-year-old plant supplies enough electricity to serve about 400,000 homes in the District and Maryland, and officials with Pepco and the D.C. Public Service Commission have described it as a vital link in the Washington power grid.

Without the plant's generating capacity, if other transmission circuits failed there could be a blackout "in much of the District of Columbia" affecting all electric customers in Georgetown, Foggy Bottom and major portions of downtown Washington, Pepco wrote in a filing last week with the Federal Energy Regulatory Commission.

"Numerous federal facilities will lose power, including those crucial to the security, safety and welfare of the whole country, such as the FBI, the Justice Department, the State Department,'' wrote Pepco, which distributes electric power in the region.

Officials at Pepco and the D.C. Public Service Commission acknowledged last week that the plant's shutdown has not yet affected the power supplied to residents. "So far, we've gotten by because we haven't had the kind of conditions that could lead to sudden blackouts, like equipment failures, and we've had relatively mild weather,'' said D.C. public service Commissioner Richard E. Morgan.

"But it still could happen,'' he added.

Pepco said it does not plan on letting things get to that point. The company announced that it plans to work with the D.C. commission to accelerate construction of new transmission facilities that would ensure reliable electric power even without the Mirant plant.

"Given Mirant's recent decisions, we believe action is necessary to satisfy Pepco's obligation to provide reliable service to our customers,'' said Dennis Wraase, president and chief executive officer of Pepco Holdings Inc. The transmission construction project is expected to take about 18 months.

For now, Pepco said it supports the D.C. Public Service Commission petition asking federal regulators to order the plant to reopen. Brian Lee, a spokesman for the Federal Energy Regulatory Commission, declined to say when the commission will make a decision.

Mirant, for its part, remains determined to reopen the plant. "We're confident that we're going to find a solution that will allow us to get our plant back into service and restore the level of electric reliability that we've come to expect,'' Mirant spokesman Steve Arabia said.

The report that precipitated the shutdown looked at worst-case scenarios involving pollution, weather and operational capacity. Researchers found that under certain conditions, the levels of sulfur dioxide, nitrogen dioxide and particles in the vicinity of the Mirant plant are higher than national ambient air quality standards allow.

As a result, state officials directed Mirant to take immediate steps to reduce pollution from the plant. Mirant decided to shut the plant down until it could find a way to meet air quality standards.

Atlanta-based Mirant, which filed for bankruptcy in 2003, operates four plants in the Washington area, including three in Maryland: in Montgomery, Prince George's and Charles counties.

Neighbors of the Alexandria plant, on the banks of the Potomac in the northern end of the city, have complained for years about what they believed to be high levels of mercury, contaminants in the air and water, and of a sooty substance that they say covers surfaces around their homes and gardens.

Poul Hertel, a neighbor who has helped lead the fight against the plant, said he is skeptical about Mirant's plan to reopen on a limited basis. He said the problem of polluted downwash from the plant's smokestacks could actually worsen.

"Downwash is not proportional to how much they are producing, it's more proportional to the speed and velocity of the emissions,'' Hertel said. "Just because they are operating at lowered capacity doesn't mean the issue is by any way, shape or form resolved.''

In the end, Hertel said, he believes the plant probably will have to close. "Everything suggests that this plant is just not suitable or compatible with its surroundings,'' he said. "The health effects are too significant to ignore or negotiate away.''