When permitting a new or modified source in an area that is designated as in attainment with federal or state air quality standards, a facility can be required to demonstrate that any increase in emissions will not result in an exceedance of any National Ambient Air Quality Standard (NAAQS) or the allowable PSD increments.
Emissions are modeled using regulatory-approved dispersion modeling procedures. The model results are added to background concentrations that are representative of the impacts from minor sources located in the area. The results of this analysis are compared to the appropriate NAAQS.
The PSD increment analysis also estimates the impacts of permitted sources using dispersion modeling techniques but only considers emission increases that have occurred since the baseline date for each applicable pollutant.
The study was to demonstrate that operation of a petroleum refinery following modifications to its permit to operate, in conjunction with other major and minor sources in the area, would not result in an exceedance of any National Ambient Air Quality Standards (NAAQS) or the allowable PSD increments.
Verdant assessed the emission increase resulting from modifications to the client’s facility. To prepare a comprehensive inventory of sources that could contribute to potential violations of NAAQSs or to consumption of the increment, Verdant personnel then identified all permitted sources within a 50 kilometer radius of the refinery and reviewed the permit files for each to determine maximum allowable emissions from each facility and any changes in emissions that had occurred since the applicable baseline date
The air quality analysis demonstrated that proposed changes to the refinery would not result in an exceedance of any of the NAAQS or allowable increments despite the use of worst case emission estimates and dispersion models which are known to be conservative.