From: "Darcy Wilson" <Darcy.Wilson@erg.com>

To: <henk.VanDerMeyden@alcoa.com>, <Michael.Palazzolo@alcoa.com>, Rochelle Boyd/RTP/USEPA/US@EPA

Cc: Ted Palma/RTP/USEPA/US@EPA, Anne Pope/RTP/USEPA/US@EPA, "Darcy Wilson" < Darcy.Wilson@erg.com>, "Stacie Enoch"

<Stacie.Enoch@erg.com>, "Christopher Holder" <CHolder2@icfi.com>

Date: 12/29/2010 01:52 PM

Subject: Re: Fwd: Potline Roof Monitor Questions

- Alumax of South Carolina

ERG's replies relative to the emission inventory data file are provided below. Rochelle and the modelers

are best to answer questions 2

- 4 though.

Darcy Wilson

Vice President

Eastern Research Group, Inc

1600 Perimeter Park Drive

Morrisville, NC 27560

919

- 468

- 7860 (voice)

919

- 468

- 7801 (fax)

darcy.wilson@erg.com

>>> "Van Der M eyden, Henk" <Henk.VanDerMeyden@alcoa.com> 12/21/2010 1:32 PM >>>

Anne/Darcy,

Cheryl Kirkland and I have been busy with updating the stack parameter

information for the potline roof monitors at the Alumax of South

Carolina smelter as part of EPA's residua l risk modeling efforts under

the primary aluminum MACT. I attached some screen captures from Google

Earth in a PowerPoint and a DRAFT Release Point spreadsheet to help

clarify our questions.

<<Potroom Roof Monitors as Point Sources2.pptx>>

<<ReleasePoi nt_NEI41217_revisedDec2010_HJV.xls>>

In both the as

- received kmz file and Emission Release Point spreadsheet,

there appears to be a double counting of the potline roof monitors. One

set of roof monitor points (Sources 66

- 69) is by Potroom Group (See NSP S

regulations 60.191). This is how the roof monitors were originally

permitted in 1979 and how they continue to be represented in our Title V

permit and annual emissions inventory. In the as

- received kmz file,

these source were also incorrectly located a s shown on the first screen

capture slide. The second slide shows the corrected location of these

sources in the center of the courtyard of the Potroom Group that they

represent. EPA added a second set of emission release points (Sources

69a

- 69d) center ed on the middle of each Potroom Roof. In both

instances, there is only a single point representing a Potroom roof.

The description of these sources is reversed in that Source 69a

(Emission Unit ID RV_101) should be the southern

- most Potroom roof vent.

Our questions:1.Which sources will be used to model the Potline roof monitors

and how do we ensure that there is no double counting of the roof

emissions if we have both the permitted Potroom Group and EPA's added

Potroom emission release points to repres ent the roof monitors?

Release points 66 through 69 are associated with prebake fugitive emissions according to the SCC code.

The pollutants covered are manganese, arsenic, chromium, nickel, hydrogen fluoride.

Release points 69a through 69d are as sociated with roof vents according to the SCC code. The pollutants

covered are speciated POM and naphthalene.

Because these release points appear to be representing different processes and there is no overlap between

the pollutants covered by each gro up, these do not actually appear to be duplicates. You can view the

records associated with each release point in the "CategoryHAPs_NEI41217.xls" file. If you believe

some of the records are in fact duplicates, you should enter a comment for the duplicat e records in the

category HAPs spreadsheet so we will know which ones to remove.

2.We corrected the location of Sources 66

- 69 by placing them in

the center of each courtyard in the emission release point spreadsheet.

That is how they are permitted. If So urces 66

- 69 will be used to

represent the roof monitors, then is the center of the courtyard the

right location to locate the source for modeling?

According to the SCC code, release points 66 through 69 are associated with prebake fugitive emissions

d escribed above. This is a question for the modelers. You may enter a comment in the release point

spreadsheet if you are unsure about the revised locations.

3.EPA is only showing a single point to represent a Potroom roof

or Potroom Group roof, not the 11 points to represent a line source as

was discussed in the December 14 conference call. Representing a ~1900

ft roof monitor as a single point is not correct. How should we address

this in the release point spreadsheet? Are we to add 10 points for eac h

Potline roof monitor, 5 on each side of the center? If so, how are we

to do that and where based on the previous question?

This is a question for Rochelle or the modelers. You should include a comment in the release point

spreadsheet identifying th e release points that should be modeled as line sources.

4.Initial corrections (location coordinates, stack height, and

temperature) have been made to the Release Point spreadsheet along with

comments. What changes do we need to make to the Release Po int

Spreadsheet regarding the stack diameter and velocity to properly

represent the line source?

This is a question for the modelers. Previously the line sources were modeled with default fugitive

parameters for temperature (72 degrees F), diameter (0. 003 ft), velocity (0.0003 ft/sec), and flow rate (0

cuft/sec). Original height values were retained.

Mike Palazzolo and I will be on vacation until 01/03/11 but we would

like to discuss these questions via conference call sometime in thefirst week of J anuary so that we can still get all the information back

to you by the 01/14/11 date.

Happy Holidays.

Henk van der Meyden, PG

Environmental Manager

Alcoa

- Mt. Holly (dba Alumax of South Carolina)

Office: (843) 572

- 5361

Cell: (843) 296

- 3359

Fax: (843) 5 72

- 5378