§204.1120. Air Quality Models  


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  • a)         All estimates of ambient concentrations required under this Section shall be based on applicable air quality models, databases, and other requirements specified in 40 CFR 51, appendix W (Guideline on Air Quality Models) (incorporated by reference in 35 Ill. Adm. Code 204.100).

     

    b)         When an air quality model specified in 40 CFR 51, appendix W (Guideline on Air Quality Models) (incorporated by reference in Section 204.100) is inappropriate, the model may be modified or another model substituted.  Such a modification or substitution of a model may be made on a case-by-case basis or, where appropriate, on a generic basis for a specific State program.  Written approval of USEPA must be obtained for any modification or substitution.  In addition, use of a modified or substituted model must be subject to notice and opportunity for public comment under procedures set forth in 35 Ill. Adm. Code 252.