Historically CALPUFF air dispersion modeling has been a useful tool for determining ambient concentrations, regional haze, and deposition in Class I areas for Prevention of Significant Deterioration (PSD) applications. Until recently, CALPUFF has not been utilized by minor sources for small permitting projects or for near- field regulatory analyses due to the costs encountered from the complexity of the model and the extensive computer resources it requires. However, as shown in this case study, CALPUFF dispersion modeling for near- field analyses can provide significant cost savings and additional permit flexibility, even for minor sources of emissions. As the capabilities of computers grow, CALPUFF will most-likely play an increasingly important role in air permitting and regulatory review of near field analyses, even in minor source reviews. This case study provides a dramatic comparison of a variety of air dispersion models including ISCST3, CALPUFF-Lite, CALPUFF, and CALPUFF with Complex Terrain Sub-Grid (CTSG) receptors. Furthermore, the results of this case conclude that CALPUFF’s ability to calculate chemical transformation and deposition as well to incorporate terrain affects on plume dispersion
allow for more realistic dispersion representation and reduce overestimation of dispersion impacts.