Good Engineering Practice (GEP) stack height is an important concept both in air permitting and in AERMOD air dispersion modeling. The GEP Stack Height View in BREEZE Downwash Analyst allows the user to view the GEP stack height for a particular stack. By moving a slider, users can adjust the wind direction to see how the GEP calculations change. Downwash Analyst also gives a 3D view of the stack, buildings, wind direction, and GEP stack height, making it instantly clear what a stack’s GEP height is and more importantly, which buildings are the driving force behind that height. In a case like the example image, a single wind direction will allow multiple buildings to possibly cause downwash. Downwash Analyst automatically highlights the one structure (or combinations of structures) that cause the greatest GEP height, which is also the one structure that AERMOD will “see” and use for downwash purposes with that wind direction.
GEP Max Stack Height View
To further simplify things, the GEP Max Stack Height View automatically selects the wind direction that produces the maximum GEP stack height, and highlights the building that caused that maximum value.