35 Ill. Adm. Code 204.250
Baseline Area
Section 204.250 Baseline Area
a) "Baseline
area" means any intrastate area (and every part thereof) designated as
attainment or unclassifiable under section 107(d)(1)(A)(ii) or (iii) of the CAA
(42 USC 7407(d)(1)(A)(ii) or (iii)) in which the major source or major
modification establishing the minor source baseline date would construct or
would have an air quality impact for the pollutant for which the baseline date
is established, as follows: Equal to or greater than 1 μg/m
3
(annual average) for SO
2
, NO
2
, or PM
10
; or
equal to or greater than 0.3 μg/m
3
(annual average) for PM
2.5
.
b) Area
redesignations under section 107(d)(1)(A)(ii) or (iii) of the CAA cannot
intersect or be smaller than the area of impact of any major stationary source
or major modification that:
1) Establishes
a minor source baseline date; or
2) Is
subject to this Part and would be constructed in the state proposing the
redesignation.
c) Any
baseline area established originally for the TSP increments shall remain in
effect and shall apply for purposes of determining the amount of available PM
10
increments, except that such baseline area shall not remain in effect if the Agency
rescinds the corresponding minor source baseline date in accordance with
Section 204.520(c).