SUBTITLE B: AIR POLLUTION
CHAPTER I: POLLUTION CONTROL BOARD
SUBCHAPTER a: PERMITS AND GENERAL PROVISIONS
PART 203 MAJOR STATIONARY SOURCES CONSTRUCTION AND MODIFICATION
SECTION 203.1800 LOWEST ACHIEVABLE EMISSION RATE
Section 203.1800 Lowest Achievable Emission Rate
a) The owner or operator of a new major stationary source shall demonstrate that the control equipment and process measures applied to the source will produce LAER for each regulated NSR pollutant for which the stationary source is major.
b) Except as provided in subsections (d) or (e), the owner or operator of a major modification shall demonstrate that the control equipment and process measures applied to the major modification will produce LAER for each regulated NSR pollutant for which the modification is major. This requirement applies to each emissions unit at which a net increase in emissions of the regulated NSR pollutant has occurred or would occur as a result of a physical change or change in the method of operation in the emissions unit.
c) The owner or operator shall provide a detailed showing that the proposed emission limitations constitute LAER. Such demonstration shall include:
1) A description of the manner in which the proposed emission limitation was selected, including a detailed listing of information resources,
2) Alternative emission limitations, and
3) Such other reasonable information as the Agency may request as necessary to determine whether the proposed emission limitation is LAER.
d) If the owner or operator of a major stationary source (other than a source which emits or has the potential to emit 100 tpy or more of VOM or NOX) located in an area classified as serious or severe nonattainment for ozone does not elect to provide internal offsets for a change at the source in accordance with Section 203.1220(d), such change shall be considered a major modification for purposes of this Part, but in applying this Section in the case of any such modification, the BACT, as defined in section 169 of the CAA (42 U.S.C. 7479), shall be substituted for the LAER. BACT shall be determined in accordance with policies and procedures published by the USEPA.
e) In the case of any major stationary source of VOM or NOX located in an area classified as serious or severe nonattainment for ozone which emits or has the potential to emit 100 tpy or more of VOM or NOX, respectively, whenever any change at that source results in a significant increase in emissions of VOM or NOX, respectively, from any discrete operation, unit, or other pollutant emitting activity at the source, such increase shall be considered a major modification for purposes of this Part, except that if the owner or operator elects to offset the increase by a greater reduction in emissions of VOM or NOX, respectively, from other operations, units or activities within the source at an internal offset ratio of at least 1.3 to 1, the requirements of this Section concerning LAER shall not apply.
(Source: Added at 49 Ill. Reg. 6237, effective April 23, 2025)