NSR Air Quality Modeling

The Air Division is responsible for the review and approval of the air quality analysis required to comply with the New Source Review Prevention of Significant Deterioration Program. The review of the air quality analysis follows the guidelines: “Guideline on Air Quality Models (Revised)” 40 CFR, Part 52, Appendix W and the “New Source Review Workshop Manual: Prevention of Significant Deterioration and Non-attainment Area Permitting (Draft 1990)”.

Class I Areas

New and modified stationary sources in Mississippi have the potential to impact the Sipsey and Breton Class I Wilderness Areas located in Alabama and Louisiana, respectively. The Federal Land Manager should be contacted for guidance in assessing the impacts in these areas.

Emissions Inventories

When a full impact analysis is required for any pollutant, the applicant is responsible for establishing the necessary inventories of existing sources and their emissions, which will be used to carry out the required NAAQS and PSD increment analyses. Current inventories can be obtained through the MDEQ Air Division by following the above link.

Minor Source Baseline Date

The minor source baseline date is the earliest date after the trigger date on which a complete PSD application is received by the permit reviewing agency. This date marks the point in time after which actual emissions changes from all sources affect the available increment. The minor source baseline dates for counties in Mississippi can be viewed by clicking the above link.

Met Data

Five years of representative meteorological data should be used when estimating concentrations with an air quality model. Met data preprocessed using AERMET for stations in and near the State can be downloaded using the above link.

Nearby Sources

All sources expected to cause a significant concentration gradient in the vicinity of the source or sources under consideration for emission limit(s) should be explicitly modeled. The “North Carolina 20D Rule” can be applied to the emissions inventory to determine sources which are not expected to cause a significant concentration gradient. A copy of the rule can be downloaded by clicking on the “Nearby Sources” link above.