NAC445B.054. “Dispersion technique” defined.

     1. “Dispersion technique” means any technique that attempts to affect the concentration of a pollutant in the ambient air by:

     (a) Using that portion of a stack which exceeds good engineering practice stack height;

     (b) Varying the rate of emission of a pollutant according to atmospheric conditions or ambient concentrations of that pollutant; or

     (c) Increasing final exhaust gas plume rise by manipulating source process parameters, exhaust gas parameters or stack parameters, combining exhaust gases from several existing stacks into one stack or other selective handling of exhaust gas streams so as to increase the exhaust gas plume rise.

     2. The term does not include:

     (a) The reheating of a gas stream, following use of a pollution control system, for the purpose of returning the gas to the temperature at which it was originally discharged from the facility generating the gas stream.

     (b) The merging of exhaust gas streams where:

          (1) The source owner or operator demonstrates that the facility was originally designed and constructed with such merged gas streams;

          (2) After July 8, 1985, such merging is part of a change in operation at the facility that includes the installation of pollution controls and is accompanied by a net reduction in the allowable emissions of a pollutant. This exclusion from the definition of “dispersion techniques” applies only to the emission limitation for the pollutant affected by such a change in operation; or

          (3) Before July 8, 1985, such merging was part of a change in operation at the facility that included the installation of emissions control equipment or was carried out for sound economic or engineering reasons. Where there was an increase in the emission limitation or, in the event that no emission limitation was in existence before the merging, an increase in the quantity of pollutants actually emitted before the merging, the Director shall presume that merging was significantly motivated by an intent to gain emissions credit for greater dispersion. Absent a demonstration by the source owner or operator that merging was not significantly motivated by such an intent, the Director shall deny credit for the effects of such merging in calculating the allowable emissions for the source.

     (c) Smoke management in agricultural or silvicultural prescribed burning programs.

     (d) Episodic restrictions on residential woodburning and open burning.

     (e) Techniques under paragraph (c) of subsection 1 which increase final exhaust gas plume rise where the resulting allowable emissions of sulfur dioxide from the facility do not exceed 5,000 tons per year.

     (Added to NAC by Environmental Comm’n by R096-05, eff. 10-31-2005)