Admin. R. Mont. 17.8.825
(4) The owner or operator of a proposed source or modification may demonstrate to the federal land manager that the emissions from such source would have no adverse impact on the air quality-related values of such lands (including visibility), notwithstanding that the change in air quality resulting from emissions from such source or modification would cause or contribute to concentrations which would exceed the maximum allowable increases for a Class I area. If the federal land manager concurs with such demonstration and so certifies to the department, the department may, provided that applicable requirements are otherwise met, issue the permit with such emission limitations as may be necessary to assure that emissions of sulfur dioxide (SO 2 ), particulate matter, and nitrogen oxides would not exceed the following maximum allowable increases over the minor source baseline concentration for such pollutants:
| Pollutant | Maximum allowable increase (micrograms per cubic meter) |
PM-2.5
annual arithmetic mean..........................................................................................4
24-hr maximum........................................................................................................9
Particulate matter:
PM-10, annual arithmetic mean...........................................................................17
PM-10, 24-hr maximum.........................................................................................30
Sulfur dioxide (SO 2 ):
annual arithmetic mean.........................................................................................20
24-hr maximum......................................................................................................91
3-hr maximum......................................................................................................325
Nitrogen dioxide (NO 2 ):
annual arithmetic mean.........................................................................................25
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(5) The owner or operator of a proposed source or modification which cannot be approved under procedures developed pursuant to (4) may seek to obtain a sulfur dioxide variance from the Governor.
(6) In the case of a permit issued under procedures developed pursuant to (5), the source or modification shall comply with emission limitations as may be necessary to assure that emissions of sulfur dioxide from the source or modification would not (during any day on which the otherwise applicable maximum allowable increases are exceeded) cause or contribute to concentrations which would exceed the following maximum allowable increases over the baseline concentration and to assure that such emissions would not cause or contribute to concentrations which exceed the otherwise applicable maximum allowable increases for periods of exposure of 24 hours or less for more than 18 days, not necessarily consecutive, during any annual period:
MAXIMUM ALLOWABLE INCREASE
[Micrograms per cubic meter]
| Terrain Areas | ||
| PERIODS OF EXPOSURE | Low | High |
| 24-hr maximum................................................................................................................ | 36 | 62 |
| 3-hr maximum.................................................................................................................. | 130 | 221 |
Authorizing statute(s): 75-2-111, 75-2-203, MCA
Implementing statute(s): 75-2-202, 75-2-203, 75-2-204, MCA
History: NEW, 1993 MAR p. 2919, Eff. 12/10/93; AMD, 1994 MAR p. 2829, Eff. 10/28/94; TRANS, from DHES, 1996 MAR p. 2285; AMD, 2002 MAR p. 3567, Eff. 12/27/02; AMD, 2011 MAR p. 2134, Eff. 10/14/11.