New Mirant News

Plant Operations Have Been Significantly Reduced; Full Shut Down to Occur

   Unless Acceptable Interim Operating Plan Can Be Identified by Wednesday

    ALEXANDRIA, Va., Aug. 22 /PRNewswire-FirstCall/ -- Mirant Corp.

(Pink Sheets: MIRKQ) announced today that it has taken rapid action to address

concerns raised by a just-completed environmental computer modeling study of

air quality in the vicinity of Mirant's Potomac River generating station.

    Mirant said that, as its initial response to the study findings, it has

already reduced output of all five units at the plant to their lowest feasible

levels.

    Mirant said it expects to meet soon with the Virginia Department of

Environmental Quality (DEQ) to discuss both short and long-term plans to

resolve the newly identified local air quality issues. If no acceptable

short-term solutions can be found, Mirant will shut down all five units at the

power plant no later than midnight Wednesday, August 24, until a solution can

be identified and implemented.

    Even taking the new study findings into consideration, the Potomac River

generating station remains in compliance with all its operating permits, which

set overall limits on the quantity of emissions from the plant, the company

said.

    The coal-fired power plant, which began operation in 1949, produces 482

megawatts of electricity for Washington D.C. and surrounding communities. It

is located in Alexandria, VA. The plant has been identified as a critical

component for the reliability of the electric grid in the Washington, D.C.

area.

    "As soon as we received results of an environmental computer modeling

analysis that showed emissions from the Potomac River generating station could

be significantly contributing to localized, modeled exceedances of National

Ambient Air Quality Standards (NAAQS), we acted quickly," said Curt Morgan,

executive vice president and chief operating officer, Mirant.

    "However, it's important to understand the nature of the study that has

just been completed. The computer model was designed to analyze local air

quality levels using a 'worst case' set of assumptions, including the

operation of all five units at maximum permitted output with maximum

emissions, combined with unfavorable wind conditions.  These combined

circumstances do not typically occur all at once, so the model works with

hypothetical conditions that are not usually seen during normal plant

operation," Mr. Morgan said. "Nevertheless, we take these findings extremely

seriously, as demonstrated by our actions."

    "The decision to curtail and possibly halt power production at the plant

involves many complex issues, including important electric system reliability

considerations in the Nation's Capital and throughout the Mid-Atlantic region.

We are working closely with all affected parties. However, the overriding

factor in our decision has been, and will continue to be, protection of public

health," said Lisa D. Johnson, president, Mirant's Northeast and Mid-Atlantic

business unit.

    The plant has been designated by PJM Interconnection, the entity

responsible for the reliability of the transmission system from the Mid-

Atlantic states as far west as Chicago, as a facility critical to electric

system reliability in the Washington, D.C. area. PJM's designation means that

removing the Potomac River generating station could result in a strain on the

transmission system and potential electrical outages if other key generation

and transmission facilities become unavailable during high demand periods.

    Because of the advance notice required to be given to the regional

electric grid operator and the complex and lengthy physical process to shut

down large coal-fired steam boilers, Mirant will continue to operate the plant

at a reduced level for a few days.

    The company also noted that it will maintain the plant in a state of

operational readiness during the period of reduced operations or temporary

shutdown of all units.

    The new findings arose in a study completed August 19, 2005. It was

commissioned under an agreement between Mirant and the Virginia Department of

Environmental Quality (DEQ).  The computer modeling of five air pollutants

from the plant showed that for three types of emissions -- PM10 (particulate

matter with an aerodynamic diameter of 10 micrometers or smaller), NO2

(nitrogen dioxide), and SO2 (sulfur dioxide) -- the plant's emissions have the

potential to contribute to localized, modeled exceedances of NAAQS under some

conditions.

    The potential localized air quality concerns impact an area within a

half-mile radius of the plant. The newly identified air quality impacts are

the result of a phenomenon known as "downwash." According to the U.S.

Environmental Protection Agency, downwash is defined as "impacts associated

with building wake effects.  These effects cause the pollutant plume to fall

to ground-level quicker." At the Potomac River plant, the unique combination

of relatively short emissions stacks at the power plant (165 feet) and the

presence of nearby tall buildings -- built well after the power plant was

completed -- produce conditions that the newly completed computer model

identified as being capable of causing downwash under some wind conditions.

Computer modeling of possible downwash effects had never previously been

required or conducted at the Potomac River plant.

    "Although the exact time frame for the return to full service of the

Potomac River power plant cannot currently be determined, we are confident

that we can identify solutions, and hopeful we can gain the cooperation of all

parties to implement them," Ms. Johnson said.

    Mirant said it does not expect to return the plant to full service until

appropriate solutions are implemented. However, Mirant may be required to

operate the plant to meet mandatory system stability obligations, or if there

is a legal obligation to operate the plant at higher output levels than would

otherwise be in effect. Mirant also said it will need to operate plant units

occasionally to test technological modifications to the plant.

    Mirant is a competitive energy company that produces and sells electricity

in the United States, the Caribbean, and the Philippines. Mirant owns or

leases more than 18,000 megawatts of electric generating capacity globally.

The company operates an asset management and energy marketing organization

from its headquarters in Atlanta. For more information, please visit

http://www.mirant.com.

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