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Choi, David

From: Jeremy G. Heiken [JHeiken@sierraresearch.com]

Sent: Wednesday, June 19, 2013 8:42 AM

To: Choi, David; Michaels, Harvey

Cc: Beardsley, Megan; Yanca, Catherine

Subject: RE: Tier 3 NPRM converstion from monthly to annual

I understand.  I just needed to check.  I understand non‐linearities in play and options for obtaining annual results from 2

months of inventory results.

Jeremy

From: Choi, David [mailto:Choi.David@epa.gov] 

Sent: Wednesday, June 19, 2013 8:40 AM 

To: Jeremy G. Heiken; Michaels, Harvey 

Cc: Beardsley, Megan; Yanca, Catherine 

Subject: RE: Tier 3 NPRM converstion from monthly to annual 

Jeremy,

For pollutants except PM, we applied equal weighting factors of 5.88 to both Jan and July ton numbers to get to annual

tons.  For PM, different weighting factors for Jan and July were required because PM has a particular sensitivity to colder

temperatures, thus using the “winter” value for half the year would overstate emissions.  Based on the annual PM

analysis from the RFS2 rule, we calculated PM weighting factors of 4.3 and 7.5 for Jan and July, respectively.  

However, in the Tier 3 NPRM inventory analysis, the weighting factors were unintentionally switched; 7.5 was applied

for Jan, and 4.3 for July.  This error led to a slight overestimation in the NPRM’s national PM inventories.  However,

because the error was made for both the control and reference case, the impact on projected reductions from Tier 3 is

small.  Note, this problem is found only in the national inventory estimates and does NOT affect the AQ modeling

results.  We will, of course, correct this in the analysis for the Tier 3 FRM.   

Please feel free to let me know if you have any additional questions.

Thanks,

David

From: Jeremy G. Heiken [mailto:JHeiken@sierraresearch.com] 

Sent: Monday, June 17, 2013 9:48 AM 

To: Choi, David; Michaels, Harvey 

Cc: Beardsley, Megan; Yanca, Catherine 

Subject: RE: Tier 3 NPRM converstion from monthly to annual 

David,

This does work out exactly, but I do realize I have one more question.  What is the context behind the unique seasonal

weighting for PM?

Jeremy
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From: Choi, David [mailto:Choi.David@epa.gov] 

Sent: Monday, June 17, 2013 8:46 AM 

To: Jeremy G. Heiken; Michaels, Harvey 

Cc: Beardsley, Megan; Yanca, Catherine 

Subject: RE: Tier 3 NPRM converstion from monthly to annual 

Jeremy,

The annual ton estimates in Table 7‐15 of the RIA were generated by running a national scale run of Jan & July only and

using the equation below.

For PM,

‐ Emission (US Short Tons) = January emission (in grams) * 7.5 / 907,200 + July emission (in grams) * 4.3 /

907,200

For all other pollutants,

‐ Emission (US Short Tons) = (Jan + July) * 5.88 / 907,200

Please let me know if you have any questions.

Thanks,

David

From: Jeremy G. Heiken [mailto:JHeiken@sierraresearch.com] 

Sent: Friday, June 14, 2013 5:36 PM 

To: Michaels, Harvey 

Cc: Beardsley, Megan; Choi, David; Yanca, Catherine 

Subject: RE: Tier 3 NPRM converstion from monthly to annual 

The RIA.  Thanks.

From: Michaels, Harvey [mailto:Michaels.Harvey@epa.gov] 

Sent: Friday, June 14, 2013 4:25 PM 

To: Jeremy G. Heiken 

Cc: Beardsley, Megan; Choi, David; Yanca, Catherine 

Subject: RE: Tier 3 NPRM converstion from monthly to annual 

Jeremy,

Table 7‐15 from precisely which document?  I wrote very little of the Tier 3 NPRM documents, so I am copying others

who may know where the numbers you are referring to came from.  Please reply to all.

Thanks.

Harvey Michaels

U.S.EPA, Office of Transportation and Air Quality

Assessment and Standards Division

734‐214‐4184
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From: Jeremy G. Heiken [mailto:JHeiken@sierraresearch.com] 

Sent: Friday, June 14, 2013 10:56 AM 

To: Michaels, Harvey 

Subject: Tier 3 NPRM converstion from monthly to annual 

Harvey,

I just want to confirm a number as precisely as possible to make sure my Tier 3 set up matches that used by you.  I am

trying to match the 3,167,934 value in Table 7‐15 (control case annual tons of NOx for 2017).  I am very close.  I believe

the difference is in the assumption to convert from monthly grams to annual tons.  See attached.   Can I get the formula

y’all used to go to annual tons?

Jeremy

Jeremy Heiken

sierra research

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