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City of Alexandria, VA City of Alexandria, VA
Environmental Quality
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Page updated Sep 9, 2009 4:26 PM

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Please join us on Thursday, October 8, 2009 from 7-9 pm at City Hall Sister Cities Conference Room 1101 

OBJECTIVE: To receive public input on the proposed windscreens on three sides (North, East and South) of the coal pile at the Mirant Potomac River Generating Station (PRGS) aimed at reducing fugitive coal dust emissions from this facility.

BACKGROUND: In July 2008, Mirant Potomac River, LLC and the City of Alexandria entered an agreement to undertake the implementation of enhanced fugitive dust emissions controls (Phase I; $2 million capital costs) and stack fine particulate (PM2.5) emissions controls (Phase II; $32 million capital costs). WorleyParsons was selected as the project Engineer to conduct this implementation. The City also hired EPSCO International as the City’s Engineer to provide technical assistance to City Staff in its evaluation of the control options identified by WorleyParsons.

As a result of the Phase I project, WorleyParsons recommended the installation of the following fugitive dust emissions controls, in descending order of priority and subject to capital availability (i.e., up to a maximum of $2 million):
1. Installation of a fog-type dust suppression system at the base of both the fly ash silos for the loading of trucks and railcars.
2. Procurement of a street sweeper for the clean up of paved surfaces within the plant.
3. Installation of 30-foot windscreens on three sides (North, East, and South) and the replacement of the west side windscreen adjacent to the coal storage pile.
4. Addition of drip pans and drain piping under the remainder of coal conveyors G1 and G2 and all of coal conveyors C1 and C2.
5. Replacement of the existing ash loader with a new design under the fly ash silo A.

City staff previously recommended to the MCMG (Mirant Community Monitoring Group) to proceed immediately with options 1, 2 and 4. Option 3, i.e., the proposed 30-ft windscreens, could potentially have significant visual impact on the neighboring community and thus public input is being sought before the MCMG and staff make final recommendation to the City Council.  


The proposed windscreens are designed to be 50% porous and reduce the wind speed upon impact. This, in turn, reduces coal dust pick-up as depicted in this figure. To be most effective, windscreen height should be the same as the pile height, necessitating the proposed height of 30 feet for this application.

From a fugitive dust control point of view, City staff concurs with WorleyParsons that the proposed windscreens would be effective in reducing the dust emissions from the coal pile. Depending on the coal pile height and wind speed, the proposed windscreens could potentially reduce the coal dust emissions by up to 60% (See Windbreak Effectiveness for Storage Pile Fugitive Dust Control).


The proposed installation at Mirant PRGS is shown in the Coal Pile Windscreen presentation. The installation includes 30-ft windscreens on three sides (North, East, and South) and the replacement of the west side windscreen adjacent to the coal storage pile.


• See the Coal Pile Windscreen presentation for a rendering of the complete installation.
• A strip of the windscreen material is hung on the south side of the coal pile for residents to observe.
• A piece of windscreen material is also attached to the fence along the rail road on the south side of the coal pile for observation.


The presence of these 30-foot windscreens might significantly alter the aesthetic aspect and look of the water front. This is an important issue that City Staff and the MCMG would like to obtain comments from the affected community before making recommendations to City Council on its installation.

1. Residents living in the immediate vicinity of the proposed installation will receive a letter during the first week of September 2009 requesting their opinion on it.
2. The City will also send letters to selected homeowners associations and citizens organizations on the same matter.
3. Residents can call Khoa Tran of the Office of Environmental Quality at 703-746-4076 or e-mail him at
4. Also, there will be a MCMG open house to discuss and obtain community feedback on October 8, 2009 at 7:00 PM – 9:00 PM at 301 King Street, City Hall Sister Cities Conference Room 1101. All residents are invited to attend this open house.