1 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 questi ons. 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 righ t 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, t hey 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 to2 accu rately 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 high

risk, the fug itive 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 Lengt h 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 northwes t

- 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 FUGI TIVE DIMENSIONS.doc)

Chris Holder Senior Associate ICF International 2222 East NC

- 54, Suite 480 Durham, NC 27713 Phone: (919) 293

- 1631 Fax: (919) 293

- 1645Attachment 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 pl aced 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 repres ent 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, respective ly. The rotation angle of each polygon is also shown.