Summary	of	Interagency	Working	Comments	on	Draft	Language	under	

EO12866/13563	Interagency	Review.		Subject	to	Further	Policy	Review.

1

Environmental Protection Agency (EPA): Proposed Rule

Cross-State Air Pollution Rule for the 

2008 Ozone National Ambient Air Quality Standards

RIN 2060-AS05

Technical Support Document (TSD): Preparation of Emissions Inventories for the 

Version 6.2 2011 Emissions Modeling Platform

General Comments

1) Reviewer recommends that given the large number of exceptions, it would help to have a 

roughly quantitative estimate of how prevalent these are. For example, the section on 

spatial surrogates is one place where exceptions are handled clearly, but many other 

sections do not provide guidance on how important these exceptions are. 

a. From a bigger picture perspective, it would also be useful to have a brief 

qualitative discussion early on emphasizing that the models being used are largely 

state-of-the-art and thus, while there is likely significant uncertainty around the 

estimated emissions inventories, the approach attempts to reduce this uncertainty

through careful collection of data and benchmarking. This is an important caveat 

to the approach that should be somewhere.

Specific Comments

1) Page 3 – Reviewer recommends either pointing out where the projection methods will be 

discussed later in the TSD or discuss those methods briefly here. It looks like they are 

discussed in Section 4.

a. “Because projected emission inventories had already been prepared for the year 

2018 by the time of the Natural Resources Defense Council v. EPA decision, the 

projected emissions for some sectors were adjusted to the year 2017 using 

methods appropriate to those sectors.”

2) Page 10 (top) – Reviewer recommends understanding the degree to which the hoteling 

emission factors were imputed from nearby counties. Is this persuasive or occasional? 

How far off might the factors be?

3) Page 45 (top) – Reviewer recommends understanding what criterion was used to decide 

whether to integrate HAPs into a particular sector.

4) Page 49 (footnote 16) – How many select sources and select counties were affected by 

this error? Was this number large or small?

5) Page 57 (middle) – How much of the data is imputed with annual mean values? Is this 

appropriate rather than using seasonal mean values?

6) Page 65 (top) – For how many units is it not always possible to reallocate excess 

emissions to hours below the historic maximum and thus the regional fuel-specific 
Summary	of	Interagency	Working	Comments	on	Draft	Language	under	

EO12866/13563	Interagency	Review.		Subject	to	Further	Policy	Review.

2

average profile is used to impute the data? The graphs are beneficial, but the reviewer 

recommends providing a quantitative estimate.

7) Page 116 (bottom) – What percentage of the gas/oil play counties are covered by the 

AEO?

8) Page 152 – Reviewer recommends mentioning that VMT has largely leveled off in the 

past several years although it is beginning to is again, but that the AEO estimates, while 

showing a continued increase, are still reasonable forecasts because they extend the 

long-term trend.