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Deb Thomas
Regional Administrator (Acting) and Deputy Regional Administrator
U.S. Environmental Protection Agency, Region 8
1595 Wynkoop Street, Mail Code 8P-AR
Denver, CO 80202-1129
July 29, 2021
Ms. Thomas,
The State of Colorado is submitting this letter to supplement the revised infrastructure state implementation plan that was submitted to the Environmental Protection Agency ("EPA") on September 17, 2018 ("Revised Infrastructure SIP"). This letter provides the EPA with additional information regarding Colorado's previously submitted assurances of adequate authority under state law to carry out the Revised Infrastructure SIP. More specifically, this letter provides a non-exhaustive overview of Colorado's authority to regulate sources of air pollution related to agriculture.
Colorado's Air Quality Control Commission ("AQCC") has the explicit authority to promulgate rules and regulations that are necessary for the proper implementation and administration of the Colorado Air Pollution Prevention and Control Act. § 25-7-105, C.R.S. In addition, Colorado's Air Pollution Control Division ("APCD") has the explicit authority to administer and enforce the air quality control programs adopted by the AQCC. § 25-7-111, C.R.S. Notwithstanding these general grants of broad regulatory authority, section 109(8)(a) of the Colorado Air Pollution Prevention and Control Act explicitly limits the AQCC's authority to regulate emissions from agricultural sources in certain circumstances.
Section 25-7-109(8)(a) provides:
            Notwithstanding any other provision of this section, the commission shall not regulate emissions from agricultural, horticultural, or floricultural production such as farming, seasonal crop drying, animal feeding operations that are not housed commercial swine feeding operations as defined in section 25-8-501.1(2)(b), and pesticide application; except that the commission shall regulate such emissions if they are "major stationary sources", as that term is defined in 42 U.S.C. sec. 7602(j), or are required by Part C (prevention of significant deterioration), Part D (nonattainment), or Title V (minimum elements of a permit program), or are participating in the early reduction program of section 112 of the federal act, or is not required by section 111 of the federal act, or is not required for sources to be excluded as a major source under this article.
As the statute makes clear, there are important carve-outs to the limited restriction on the AQCC's authority to regulate certain agricultural emissions.
First, the limitation on the AQCC's authority to regulate emissions from agriculture applies only to agricultural production; the limitation does not apply to agricultural processing or other activities related to agriculture that are not production. For example, the AQCC's regulations apply to ethanol processing facilities, see 5 C.C.R. 1001-26:A.II.R, -26:A.III.A.4, and animal waste processing operations.
Second, the Colorado Air Pollution Prevention and Control Act explicitly gives the AQCC the authority to regulate emissions from agricultural production when such emissions come from "major stationary sources," and the scope of the emissions from agricultural production the AQCC has the authority to regulate because they are major stationary sources is increasing as the nonattainment area in the state changes classification. For example, the federal Clean Air Act defines a "major stationary source" as "any stationary facility or source of air pollutants which directly emits, or has the potential to emit, one hundred tons per year or more of any air pollutant." 42 U.S.C. 7602(j). However, because the Denver Metro/North Front Range ("DMNFR") ozone nonattainment area is currently classified as "Serious," it is generally the case that any source of air pollutants in the nonattainment area that emits, or has the potential to emit, at least 50 tons per year of nitrogen oxides ("NOx") or volatile organic compounds ("VOC") is considered a major stationary source. 5 CCR 1001-5:3D.II. If the classification of the DMNFR ozone nonattainment area changes to "Severe," then any source of air pollutants in the nonattainment area that emits, or has the potential to emit, at least 25 tons per year of NOx or VOC will generally be considered a major stationary source. Id. Thus, under Colorado law and federal law, the AQCC must regulate more emissions from agricultural production as the classification of the nonattainment area changes than under previous classifications.
Third, the Colorado Air Pollution Prevention and Control Act explicitly gives the AQCC the authority to regulate emissions from agricultural production, regardless of the size of the source, to the extent that such regulations are required by Part C (prevention of significant deterioration), Part D (nonattainment), or Title V (minimum elements of a permit program) of the federal Clean Air Act. § 25-7-109(8)(a), C.R.S. As noted above, the DMNFR ozone area is a nonattainment area and, therefore, the AQCC has the authority to regulate emissions from agricultural production to the extent that such regulations are required by Part D of the federal Clean Air Act due to the DMNFR ozone area's nonattainment status.
Fourth, the Colorado Air Pollution Prevention and Control Act explicitly gives the AQCC the authority to regulate emissions from agricultural production, regardless of the size of the source, to the extent that such regulation is required by section 111 of the federal Clean Air Act. See, e.g., Colorado Department of Public Health and Environment, Memo PS98-02, Agricultural Activities Exemption (second revision, April 28, 2003) ("The statute [§ 25-7-109(8), C.R.S.] states that the exemptions would not apply ... if the source was subject to a NSPS [New Source Performance Standard]"). Section 111 of the federal Clean Air Act sets national standards of performance for new stationary sources of air pollution ("NSPS"). For example, the EPA has promulgated, pursuant to authority given to it by the federal Clean Air Act, an NSPS for grain elevators, 40 C.F.R. Part 60, Subpart DD, and the AQCC has adopted by reference this NSPS for grain elevators, 5 C.C.R. 1001-8:A. Section 25-7-109(8)(a) does not limit the AQCC's authority to regulate in this manner emissions from grain elevators, regardless of the extent to which grain elevators might be used in agricultural production. In addition, agricultural sources that are subject to an NSPS are regulated by Colorado in terms of reporting emissions and permitting through the minor source permitting program, the "Prevention of Significant Deterioration" and "New Source Review" permitting programs, and the Title V permitting program.
Fifth, section 25-7-109(8)(a) of the Colorado Air Pollution Prevention and Control Act does not prohibit the AQCC from promulgating, or the APCD from administering and enforcing, generally applicable emissions rules and regulations that happen to impact emissions from agricultural production. For example, parts 3 and 4 of title 42, article 4 of the Colorado Air Pollution Prevent and Control Act grant the AQCC the authority to regulate emissions from motor vehicles and diesel-powered vehicles, respectively. Such vehicles are not exempt from applicable emissions regulations simply because they happen to be used in agricultural production.
Emissions from agricultural production is a national issue, and the EPA is well-positioned to take the lead on addressing any problems related to emissions from agricultural production. Nevertheless, Colorado has sufficient authority under Colorado state law to implement federal requirements notwithstanding section 25-7-109(8)(a)'s narrow limitation on the AQCC's authority to regulate emissions from agricultural production. As this letter demonstrates, section 25-7-109(8)(a) of the Colorado Air Pollution Prevention and Control Act is limited in scope to agricultural production (it does not apply to other types of agricultural activity, such as agricultural processing), it contains significant exceptions (such as for regulations applicable to major stationary sources, regulations required by Part D, and regulations required under section 111 of the federal Clean Air Act), and it does not prohibit the promulgation and enforcement of generally applicable emissions standards that apply to agricultural activities.
Colorado looks forward to continuing to work with the EPA on this important matter.

Sincerely,
Garrison Kaufman
Director, Air Pollution Control Division

cc:	Adam Clark, Air Program, EPA Region 8
Jeremy Neustifter, Policy Advisor and Acting Administrator, AQCC
