UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
          OFFICE OF AIR QUALITY PLANNING AND STANDARDS
          Research Triangle Park, North Carolina 27711

                        February 22, 1992

MEMORANDUM

SUBJECT:  Distribution of Report on Procedures to Estimate
          Nitrogen Oxides (NOx) Emission Increases from Mobile
          and Area Sources for Prevention of Significant
          Deterioration (PSD) Increment Analyses

FROM:     Eric Noble
          Operating Permits Policy Section (MD-15)

TO:       New Source Review (NSR) Contacts

     Attached is a copy of the final report on estimating NOx
emissions from mobile and area sources for PSD nitrogen dioxides
increment analyses.  Additional copies may be had by downloading
from either the NSR bulletin board, which has been renamed the
Permits Programs Bulletin Board System, or the Technology Transfer
Network.

     This report differs from the draft report distributed for
review last fall.  The primary change is the removal of lookup
tables for determining worst case NOx impacts of mobile and area
sources.  The tables made it appear that, for even small increases
in NOx emissions, the estimated ambient NOx impacts were so high
that very few sources would be able to use them to avoid a full
ambient air quality dispersion analysis.  Other changes were made
to incorporate comments and suggestions you made during the reivew
process.  I appreciate the time and effort you took to provide me
with those comments.

     As you may have noted from my new byline, I am no longer
directly involved in the NSR program.  I recently transferred into
the Operating Permits Policy Section so, while this may be my final
act as a representative of the NSR Section, it is probably not my
last contact with you.  In any event, I want to express my
appreciation for all the support I've received (both internally and
from the Regions), since I joined the NSR Section.

     If you have any questions or comments on this report, you can
give me a call at (919) 541-5362.

Attachment






                            ABSTRACT

     This report presents simple methods that may be used by
reviewing agencies and permit applicatns to estimate the increase
in NOx emissions from mobile and area sources for PSD NO2 increment
applications.  This study is not intended to provide the complete
methodology for estimating NO2 increment impacts, but only to
provide the basis for a screening analysis to estimate those
impacts and to determine if a detailed analysis of NOx emissions is
required.

     A three-step screening framework is presented, as follows:

Step 1 - define the study area;

Step 2 - estimate the emissions change in the study area; and

Step 3 - distribute the emissions change throughout the study area.

Techniques are presented that may be used to relatively easily
estimate NOx emissions increases from area and mobile sources. 
Based on these emissions increases, NO2 impacts can be estimated
using air quality screening models that provide worst-case impacts
from line sources and area sources.  These impacts can then be
compared with significant impact levels to determine whether a more
detailed analysis is required.

     The methods presented in this report will not be appropriate
in many situations.   An analysis of the limitations of the methods
is presented so that these situations may be identified.

















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