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Air Quality

Air quality impacts assessments using air dispersion models are required to evaluate potential offsite air quality concentration impacts.

The resulting model must demonstrate that proposed emissions do not cause a deterioration of the established National Ambient Air Quality Standards (NAAQS) for regulated criteria air pollutants.

These air quality modeling assessments are critical to the permit review and approval process. Spirit provides accurate modeling and has the experts in house to interpret the results, ensuring timely success for our clients.

Spirit’s air dispersion modeling experts are equipped with  engineering, science and meteorological backgrounds, and decades of experience. They understand atmospheric processes for emissions from sources located at a wide variety of industries, including chemicals, petrochemicals, refining, oil and gas, power, fertilizer, carbon black, solid waste management, and glass.

Spirit assists clients on a variety of regulatory and non-regulatory projects, including:

  • Air quality impacts analysis, including cumulative offsite impacts analysis using US EPA models such as AERMOD for near-field, and CALPUFF, VISCREEN and PLUVUE II for long range transport, primarily for Class I area PSD impacts and regional haze analyses;
  • Toxics impacts analyses for state air toxics programs;
  • Specialized models such as US EPA SLAB and DEGADIS for modeling dense gas releases;
  • Odor concentration modeling for development of mitigation strategies;
  • Offsite concentration impacts and deposition analyses in support of litigation matters, including expert consulting and opinion reports, and support during claims assessment and settlement;
  • Pre-project facility siting and feasibility analysis using a combination of air dispersion modeling, and unique tools developed internally.

Several of our modeling experts have conducted source-specific Best Available Retrofit Technology (BART) modeling analyses using CALPUFF for chemical, petrochemical and fertilizer plants, and refineries. On behalf of the American Petroleum Institute, Spirit’s modeling experts have also served on teams to provide comprehensive comments to the US EPA on the 2018 and 2025 Modeling Platforms.

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