Section 243.105  Air Quality Monitoring Data Influenced by Exceptional Events

a)         The federal regulations at 40 CFR 50.14 provide that a state, federal land manager, or federal agency can seek USEPA determination that exceedances or violations of an NAAQS are directly due to an exceptional event, so that the State can exclude affected ambient air quality monitoring data from a compliance determination.  An exceptional event is a natural event or the result of human activity that is unlikely to recur and that is not reasonably controllable or preventable that meets specified criteria.  The federal rule provides that a fireworks display, a prescribed fire, a wildfire, a high wind dust event, a stratospheric intrusion, or an aggregate of events on the same day can be an exceptional event.

b)         The Agency must use the applicable procedures of 40 CFR 50.14 to obtain a USEPA determination of an exceptional event and exclusion of affected ambient air quality monitoring data if the Agency determines that the data are influenced by an exceptional event and should be excluded from a compliance determination.

c)         Ambient air quality monitoring data excluded by a USEPA determination pursuant to 40 CFR 50.14 is excluded from use for compliance determination under this Part.

BOARD NOTE:  Derived from 40 CFR 50.14.

(Source:  Amended at 45 Ill. Reg. 337, effective December 17, 2020)