Sep 09, 2020
While most air dispersion modeling analyses are focused on finding the magnitude and location of maximum ground level pollutant concentrations, the maximum concentration tells only part of the story. Is the maximum concentration a rare event, or do high concentrations occur frequently? Assessing the frequency with which high concentrations occur can be very important for certain types of modeling. For example, in assessing the odor impacts of a facility like a wastewater treatment plant, the key question may be how often do noticeable odors impact a given location, not what is the maximum odor that ever impacts a location. BREEZE AERMOD, CALPUFF, and 3D Analyst make it very easy to count the exceedances of a specified concentration threshold, and to plot those exceedances on a map. This can be a powerful tool to identify how frequently harmful or objectionable concentrations may occur, and what specific locations are most frequently impacted by those concentrations. This article will explain how to use BREEZE AERMOD and BREEZE 3D Analyst to produce an exceedance count plot that contains this information. Note that BREEZE CALPUFF can be used with BREEZE 3D Analyst to produce the same type of results.