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From: Boyd.Rochelle@epamail.epa.gov

Sent: Tuesday, January 11, 2011 2:53 PM

To: Van Der Meyden, Henk

Cc: Palazzolo, Michael A.; Charles D. Johnson; rstrieter@aluminum.org; putney.david@epa.gov; 

Fruh.Steve@epamail.epa.gov; French.Chuck@epamail.epa.gov

Subject: Clarifications of Point and Area Sources

Attachments: HOW TO DETERMINE FUGITIVE DIMENSIONS.doc

Hopefully, this will help clarify the remaining questions. Please forward 

to the other members.

----- Forwarded by Rochelle Boyd/RTP/USEPA/US on 01/11/2011 02:40 PM 

-----

From: "Holder, Christopher" <CHolder2@icfi.com> 

To: Rochelle Boyd/RTP/USEPA/US@EPA 

Cc: Anne Pope/RTP/USEPA/US@EPA, "Burch, David" 

 <DBurch@icfi.com>, "rtr@erg.com" <rtr@erg.com>, Ted 

 Palma/RTP/USEPA/US@EPA

Date: 01/11/2011 01:44 PM

Subject: RE: Alcoa database files

Rochelle,

The HAP spreadsheet and the release point spreadsheet together contain all 

the fields that we need for modeling. There's no need for us to alter 

these sheets, unless I'm missing something. They must submit both these 

sheets.

What we're telling them right now that's new is that they can submit the 

pot vent sources as fugitive (area) sources. They still can do the 

original option, which was to represent the pot vent sources as a series 

of points.

If they choose the fugitive source route for a pot vent, they must supply 

values for fugitive length, fugitive width, fugitive angle, and "stack" 

height. The other "stack" parameters (temperature, diameter, 

velocity) should be fugitive defaults (72 F temp, 0.003 ft diam, 0.0003 

ft/s vel). The coordinates should correspond to the southwest corner of 

the area source prior to rotation. See the instructions below for dealing 

with fugitive length/width/angle. 

If they choose the series-of-points route for a pot vent, they must supply 

values for stack height, temperature, velocity, and diameter, as well as 

the point coordinates. They should not feel the need to use any specific 

number of points at any specific spacing interval -- they should use as 

many points, and put them in whatever locations, as necessary to 
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accurately represent the pot vent. The total emissions of the pot vent 

must be spread evenly among all the points that represent it.

HOW TO DETERMINE FUGITIVE DIMENSIONS:

For fugitive sources, especially those that have the potential to be highrisk, the fugitive source polygons must represent the source location and 

dimensions. Often, the fugitive sources coordinates are mistakenly placed 

at the source centroid. This will skew the modeled source polygon towards 

the east of the source because Fugitive Length and Fugitive Width are 

drawn beginning at the coordinates. A poorly parameterized fugitive 

source may overlap nearby residential areas, artificially increasing 

modeled health risk.

The X Coordinate and Y Coordinate of a fugitive source must correspond to 

the southwest corner of the source polygon if it is unrotated (i.e., if 

its sides run north-south and east-west) or the western-most corner if it 

is rotated.

Fugitive Length must reflect the east-west side of the polygon when 

unrotated, or the northwest-southeast side when rotated. Fugitive Width 

must reflect the north-south side of the polygon when unrotated, or the 

southwest-northeast side when rotated. The Fugitive Angle must be between 

0 and 90 (positive value), and it reflects the angle clockwise from north.

The figure below shows four examples of how fugitive source polygons are 

created. The red dashed crosshairs represent the coordinate plane with 

north towards the top. The purple “SW” call-out bubble points to the 

southwest corner to use for the fugitive source coordinates. The L and W 

notations in the polygons represent Fugitive Length and Fugitive Width, 

respectively. The rotation angle of each polygon is also shown in the 

attached Word Document.

(See attached file: HOW TO DETERMINE FUGITIVE DIMENSIONS.doc)

Chris Holder

Senior Associate

ICF International

2222 East NC-54, Suite 480

Durham, NC 27713

Phone: (919) 293-1631

Fax: (919) 293-1645
Attachment 1: Page 1 of 1

HOW TO DETERMINE FUGITIVE DIMENSIONS:

For fugitive sources, especially those that have the potential to be high-risk, 

the fugitive source polygons must represent the source location and dimensions.

Often, the fugitive sources coordinates are mistakenly placed at the source 

centroid. This will skew the modeled source polygon towards the east of the 

source because Fugitive Length and Fugitive Width are drawn beginning at the 

coordinates. A poorly parameterized fugitive source may overlap nearby 

residential areas, artificially increasing modeled health risk.

The X Coordinate and Y Coordinate of a fugitive source must correspond to the 

southwest corner of the source polygon if it is unrotated (i.e., if its sides run 

north-south and east-west) or the western-most corner if it is rotated.

Fugitive Length must reflect the east-west side of the polygon when unrotated, or 

the northwest-southeast side when rotated. Fugitive Width must reflect the 

north-south side of the polygon when unrotated, or the southwest-northeast side 

when rotated. The Fugitive Angle must be between 0 and 90 (positive value), and 

it reflects the angle clockwise from north.

The figure below shows four examples of how fugitive source polygons are 

created. The red dashed crosshairs represent the coordinate plane with north 

towards the top. The purple “SW” call-out bubble points to the southwest corner 

to use for the fugitive source coordinates. The L and W notations in the 

polygons represent Fugitive Length and Fugitive Width, respectively. The 

rotation angle of each polygon is also shown.