Subchapter B Permits - Minor Sources (cont'd)

Technical Review

The technical review primarily relates to source identification and air emission quantification, analysis of the off-property health impacts of those emissions (consisting of either basic screen modeling or refined modeling), determination of best available control technology (BACT), and applicability of any source category or emission-based state and federal regulations.

Best Available Control Technology

The BACT evaluation is one of the main portions of the technical review. BACT is a three-tiered sequential approach. Use the tabbed information below to identify the three tiers of BACT and for additional information, see the "Learn More" sidebar on this page.


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Impacts Analysis

The other main portion of the technical review is the impacts analysis. The TCEQ regulates air quality of the state, and the Texas Clean Air Act (TCAA) empowers the TCEQ to prevent and remedy conditions of air pollution.

As a whole, a permit review ensures that the operations of a proposed facility will comply with all federal and state rules and regulations and the intent of the TCAA, and not cause or contribute to a condition of air pollution. For contaminants that do not have state or federal standards, the Air Permits Division has a flowchart available for determining if a refined air dispersion modeling and effects review is required for a permit project. If required, the flowchart outlines the scope of the air dispersion modeling and effects review. The division has separate air dispersion modeling guidelines for criteria pollutants and contaminants with state standards.

Effects Screening Levels (ESLs) are short-term (hourly) and long-term (annual) health effects guidelines used in TCEQ's air permitting process to evaluate the potential for effects to occur as a result of exposure to concentrations of constituents in the air. ESLs are based on data concerning health effects, the potential for odors to be a nuisance, and effects on vegetation. They are not ambient air standards. If predicted or measured airborne levels of a constituent do not exceed the screening level, adverse health or welfare effects are not expected. Typically, if the short-term ESL is met, the long-term ESL will also be met. However, some compounds, like benzene, have very low long-term ESLs that are the limiting factor. For additional information regarding ESLs, see the "Learn More" sidebar on this page.

Air dispersion modeling is performed on air permit applications in order to determine the impacts on nearby receptors. If the predicted concentrations from the requested emission limits for a contaminant do not exceed an ESL, the impacts review is complete. However, exceedance of an ESL does not automatically result in the denial of the permit application. Rather, exceedance of an ESL will typically result in a more in-depth review of the contaminants to determine if adverse health or welfare effects would be expected to occur, and appropriate emission limits are then determined.

To put this in perspective:

The impacts analysis for a facility emitting NOx, PM10, and benzene would consist of an evaluation to determine compliance with the National Ambient Air Quality Standards (NAAQS) for NOx and PM10. Protectiveness for benzene would be determined through comparison with the ESL.

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