Code of Federal Regulations Title 40. Protection of Environment § 40.51.35 How can my state equalize the emission inventory effort from year to year?

(a) Compiling a triennial inventory means more effort every 3 years. As an option, your state may ease this workload spike by using the following approach:

(b) For the sources described in paragraph (a) of this section, your state will have data from 3 successive years at any given time, rather than from the single year in which it is compiled.

(c) If your state chooses the method of inventorying one-third of your sources that are not Type A point sources and triennial inventory nonpoint, nonroad mobile, and onroad mobile sources each year, your state must compile each year of the 3–year period identically. For example, if a process has not changed for a source category or individual plant, your state must use the same emission factors to calculate emissions for each year of the 3–year period. If your state has revised emission factors during the 3 years for a process that has not changed, you must compute previous years' data using the revised factor. If your state uses models to estimate emissions, you must make sure that the model is the same for all 3 years.