U.S. Environmental Protection Agency
Office of Transportation and Air Quality

June 12, 2000
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NONROAD Model Status Update


An updated Draft version of the NONROAD emission inventory model
is now available on the EPA web site at: 

http://www.epa.gov/otaq/nonrdmdl.htm

This version updates the input data files to match what is being
used in the air quality modeling for the 2007 Heavy Duty Highway
Vehicle rulemaking.  Documentation of these changes can be found
in the May 31, 2000, EPA memo titled "Changes to the NONROAD
Model for the April 2000 Version Used in Support of the 2007
Heavy-Duty Diesel Engine Rule," which was submitted to the EPA
Air Docket A-99-06 and which is also available at the web site
mentioned above.  

The most substantial changes are in the projected Tier 2 and Tier
3 diesel emission factors and recreational equipment inputs. Less
substantial changes also affect all equipment types, such as
updates to equipment population estimates obtained from the Power
Systems Research (PSR) Partslink database.  Other changes include
revisions to activity (hours/year) and load factor inputs for
certain equipment types based on either new PSR data or data
provided by industry (e.g., load factors for chainsaws).  

The model and data files are being made available as part of
EPA's effort to allow public review of the methods and data
involved in this rulemaking.  EPA's guidance from May 1999 on the
use of the NONROAD model is still applicable.  In short, that
guidance, which can be found at the top of the NONROAD model web
page, emphasizes that the model is still in draft form, that we
will continue to revise and improve it, and that the resulting
outputs are subject to significant change.

At this time EPA efforts are concentrated on testing, improving,
and finalizing the model.  We are not able to direct resources
toward support or assistance in its use beyond what is needed for
purposes of testing and evaluation.  Situations may arise where
the use of a draft model in a state submittal may affect EPA's
action on the submittal; furthermore, subsequent revisions to the
model may necessitate revisions to the submittal when the model
is officially released as final.  

We certainly encourage everyone testing the NONROAD model to
continue your analyses and let us know of any questions or
problems you experience.  We look forward to working with you in
the coming months as we move toward the release of a final
version of NONROAD.  Thank you for your comments and your
continued interest in NONROAD. 

          Email: nonroad@epa.gov  (preferred method)

          Fax:  (734) 214-4939

          U.S. mail:
          *NONROAD Comments*
          US EPA Assessment and Standards Division
          2000 Traverwood Drive
          Ann Arbor MI 48105

Sincerely,

NONROAD Engine Emission Modeling Team
Assessment and Standards Division, US EPA