020-2 Wyo. Code R. §§ 2-2 - Ambient Standards for Particulate Matter

(a) PM₁₀: The ambient air standards for PM₁₀ particulate matter are:

(i) 150 micrograms per cubic meter - 24-hour average concentration with not more than one expected exceedance per year.

(A) Attainment of the 24-hour standard is determined in accordance with Appendix K of 40 CFR Part 50.

(ii) 50 micrograms per cubic meter - annual arithmetic mean.

(A) Attainment of the annual standard is determined in accordance with Appendix 1 of this chapter.

(iii) For the purpose of determining attainment of the standards, particulate matter shall be measured in the ambient air as PM₁₀ (particles with an aerodynamic diameter less than or equal to a nominal 10 micrometers), by a reference method based on 40 CFR Part 50, Appendix J and designated in accordance with 40 CFR Part 53 or an equivalent or alternate method designated in accordance with 40 CFR Part 53.

(b) PM_2.5: The primary ambient air quality standards for PM_2.5 particulate matter are:

(i) 12.0 micrograms per cubic meter (µg/m³) annual arithmetic mean concentration and 35 µg/m³ 24-hour average concentration measured in the ambient air as PM_2.5 (particles with an aerodynamic diameter less than or equal to a nominal 2.5 micrometers) by either:

(A) A reference method based on 40 CFR Part 50, Appendix L, and designated in accordance with 40 CFR Part 53 ; or

(B) An equivalent method designated in accordance with 40 CFR Part 53.

(ii) The primary annual PM_2.5 standard is met when the annual arithmetic mean concentration, as determined in accordance with 40 CFR Part 50, Appendix N, is less than or equal to 12.0 µg/m³.

(iii) The primary 24-hour PM_2.5 standard is met when the 98th percentile 24-hour concentration, as determined in accordance with 40 CFR Part 50, Appendix N, is less than or equal to 35 µg/m³.

(c) PM_2.5: The secondary ambient air quality standards for PM_2.5 particulate matter are:

(i) 15 micrograms per cubic meter (µg/m³) annual arithmetic mean concentration and;

(ii) 35 micrograms per cubic meter (µg/m³) - 98th percentile 24-hour average concentration.

(iii) Attainment of the annual and 24-hour standards is determined in accordance with Appendix N of 40 CFR Part 50.

(iv) For the purpose of determining attainment of the standards, particulate matter shall be measured in the ambient air as PM_2.5 (particles with an aerodynamic diameter less than or equal to a nominal 2.5 micrometers), by a reference method based on 40 CFR Part 50, Appendix L and designated in accordance with 40 CFR Part 53, or an equivalent or alternate method designated in accordance with 40 CFR Part 53.

(d) Ambient air, for the area bounded by Townships 40 through 52 North, and Ranges 69 through 73 West, inclusive, of the Sixth Principal Meridian, Campbell and Converse Counties, in the Powder River Coal Basin, is defined as that portion of the atmosphere, external to buildings, to which the general public has access. For surface mining operations, the application of this definition will be limited to only those lands that are necessary to conduct mining operations as determined by the Administrator of the Wyoming Air Quality Division.

Notes

020-2 Wyo. Code R. §§ 2-2

Amended, Eff. 10/13/2015. Amended, Eff. 12/20/2016. Amended, Eff. 2/5/2018. Amended, Eff. 4/30/2024.