Air Dispersion Modeling
An air pollution source may be required to perform air dispersion modeling generally due to it being a new source, having a modification at an existing source, being subject to Prevention of Significant Deterioration (PSD), or releasing air toxics. All modeling analyses will be reviewed to assure compliance with federal, state, and local rules and guidelines. The Jefferson County Board of Health’s Air Pollution Control Rules and Regulations can be found
here.
General guidance on air dispersion modeling can be found from the United States Environmental Protection Agency (EPA) and the Alabama Department of Environmental Management (ADEM):
EPA’s Support Center for Regulatory Atmospheric Modeling (SCRAM) website includes information on preferred/recommended models, screening tools, meteorological processors and guidance, and various documents on permit modeling guidance.
Applicants intending to submit a modeling compliance demonstration with a permit application are expected to meet with Air and Radiation Protection Division (ARPD) staff and to submit a modeling protocol document prior to beginning modeling efforts to save time in the permit review process and to avoid any misunderstandings. A written modeling protocol must be submitted to and approved by the ARPD staff before modeling can commence. The information that should be included within a modeling protocol can be found here.
The modeling analysis must include all source input data, modeling assumptions, and model results. Model results should be summarized by averaging times and compared with the applicable standards or increments. Maximum impacts need to be summarized further to show controlling meteorological conditions as well as maximum impact locations and elevations. Model and BPIP input and output data files and meteorological files must be submitted on CD or flash drive.
For sources subject to conducting modeling for air toxics can refer to draft guidance.
The review of modeling protocols and analyses are subject to the fee schedule for air permits.