Atmospheric Dispersion Modeling


Most of our air quality staff members are experienced in performing atmospheric dispersion modeling studies. Our modeling environment enables us to perform virtually all regulatory modeling. The models that we use most are the EPA's AERMOD, Industrial Source Complex, and SCREEN models. We can access and use any of the models approved in the EPA's Guideline on Air Quality Models. We have the latest processed, meteorological data sets available for all locations in Texas and many locations elsewhere in the U.S. We can also process raw meteorological data sets.

Waid maintains the on-call system, a set of network computers dedicated to air dispersion modeling. Modeling jobs are automatically distributed across the network to the fastest available machines.

We have developed various tools to facilitate modeling. For example, standard procedures are used to digitize facility plot plans. The appropriate building structures are then processed to determine wind-direction specific downwash parameters and to generate files in a format for use with the EPA's AERMOD and Industrial Source Complex models.

Other tools we use to facilitate modeling include programs to display and print modeling results, to input source characteristics into modeling input files, and to analyze land use features from digitized information.

We routinely access EPA's website, particularly the Support Center for Regulatory Atmospheric Modeling (SCRAM) site for support of the regulatory models. We attend hearings on and comment on changes to EPA's Guidelines on Air Quality Models and state agency guidelines. Our modeling reports and protocols are frequently updated to address ever-changing regulatory demands. They are designed to be comprehensive, while also clear and easy to understand in order to expedite the review process. Whenever possible we try to use screening techniques instead of the more rigorous and expensive refined methods which saves money for clients.