Downwash Study

Community Question

Alexandria’s City Attorney told the media that emissions reduction at Potomac River is an “illusion.” What’s your response?

The facts show that the Potomac River Generating Station has already significantly reduced emissions. Over the past three years, we have lowered our NOx emissions by 30 percent on both a rate and tonnage basis. Additionally, our agreement with the Department of Justice, the U.S. Environmental Protection Agency (EPA), the Commonwealth of Virginia and the State of Maryland ensures further emissions reductions — 29,000 tons worth — over the next several years.

Learn more about air quality at the Potomac River Generating Station»

In August 2005, power production at all five units of the Potomac River generating facility was temporarily halted in response to a directive from the Virginia Department of Environmental Quality (DEQ).

The decision to temporarily shut down the facility arose from findings of a modeling study commissioned under an agreement with the DEQ to model the air quality in the area immediately surrounding the facility (the “downwash”). The DEQ directive was based on results from the study’s computer modeling showing that air emissions from the facility have the potential to contribute to localized, modeled exceedances of the National Ambient Air Quality Standards (NAAQS) under certain infrequent “worst-case” weather conditions.

There are two important points of note. One, the study used computer modeling to analyze local air quality levels using a “worst-case” set of assumptions — including the operation of all five units at maximum permitted output at maximum emissions, combined with unfavorable wind conditions; in reality, a very rare scenario. Secondly, the study results are based on this hypothetical model only. There is no evidence that NAAQS limits were exceeded.

In early January 2006, the Department of Energy issued an interim response to Potomac River’s operating plan authorizing immediate operation, making it possible to bring the entire plant into service within approximately 28 hours if an electric reliability emergency occurs.

“After weighing all of the information, I believe an emergency situation exists, and that issuance of this order is in the public interest. This order will provide the level of electricity reliability necessary to keep Washingtonians safe and our national government running, while minimizing any environmental impact from the power station,” stated Secretary of Energy Samuel W. Bodman.