Air Quality Dispersion Modeling Guidance
NSSGA, in conjunction with Trinity Consultants, has developed an accurate computer air modeling guidance document for aggregate operations that will use actual emission data generated by the aggregates industry. This includes an extensive compilation of all current state and federal modeling policy and guidance. The guidance document also identifies states that lack comprehensive aggregate industry air modeling guidance, provides consistent guidance for those states backed by appropriate technical theory and creates a single guidance document for all aspects of how to model an aggregate facility. NSSGA’s goal is to have the document approved, adopted or recognized by regulatory agencies.
Many regulatory agencies require aggregate facilities to complete air quality dispersion modeling analyses before issuing permits. One of the most subjective and time-consuming aspects of air dispersion modeling is the modeling of sources that are fugitive in nature like those found at a typical aggregate facility. Fugitive sources can include fugitive dust from conveyor transfer points, haul roads and open storage piles, as well as emissions from crushers/screens and truck loading and unloading. The current EPA air dispersion models, Industrial Source Complex Short-Term Version 3 Model (ISCST3)1 and AERMIC Model (AERMOD),2 are able to estimate ambient concentrations from these types of fugitive sources. The models allow for categorization of fugitive sources into point, area, volume, or open pit sources (open pit sources are only available in ISCST3).
Methodologies for correctly characterizing fugitive sources are necessary due to the model’s sensitivity to certain input parameters and the lack of guidance for modeling fugitive sources. Incorrect characterization of fugitive sources can lead to unrealistic model-predicted concentrations. Often, the impacts of fugitive sources are exaggerated to the point of causing facilities to limit utilization of plant equipment to be able to demonstrate modeled compliance with air quality standards, while nearby monitors show only minimal concentrations.
The Air Quality Dispersion Modeling document provides methods for appropriately characterizing fugitive sources such that the modeled parameters, and thus calculated concentrations, accurately reflect the sources in question. Discussions on regulatory guidance are included, as well as summaries of the data and technical theory used to develop the suggested methodologies.
The set of fugitive source modeling methodologies presented in this document was developed by a combination of data research, review of modeling guidance documents, and practical knowledge of modeling fugitive sources. These modeling methodologies can be adapted to fit site specific characteristics.
To obtain you copy of the NSSGA Modeling Fugitive Dust Sources click here.
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