 1 
 
NOTICE OF RULEMAKING HEARING  
 
Regarding proposed revisions to:  
 
Ozone State Implementation Plan (SIP)  
Regulation Number 7  & Regulation Number 21  & Regulation Number 25 & 
Regulation Number 26 & Air Quality Standards, Designations, and Emission  Budgets  
 
5 CCR 1001- 9 & 5 CCR 1001 -25 & 5 CCR 1001- 29 &  
5 CCR 1001- 30 & 5 CCR 1001- 14 
 
SUBJECT:  
The Air Quality Control Commission will hold a rulemaking hearing to consider  revisions to reduce 
emissions of ozone precursors and other pollutants for purposes of, withou t limitation, attaining the 
federal National Ambient Air Quality Standard for ozone  and improving public health and welfare, 
consistent with the  proposal from the Air Pollution Control Division (“Division”) . This propos al include s 
revisions to Colorado’s S tate Implementation Plan (SIP) and revisions to assoc iated regulations, both in 
and outside of the SIP.  
 
The proposal by Division includes two components to  be addressed by the Commission:  
 
(1) SIP Revisions:  
a. Ozone Nonattainment Area SIP Elements  revision s to include the Severe SIP element for the 
Denver Metro and North Front Range (DMNFR) 2008 Ozone Nonattainment Area and  severe SIP 
elements specific to the withdrawn emission inventories, attainment demonstration, and motor 
vehicle emission budgets (MVEB) ; and non- substantive, administrative updates to the severe SIP 
elements specific to enhanced monitoring, reasonable further progress, reasonably available 
control technology (RACT), reasonably available control measures (RACM), motor vehicle 
inspection an d maintenance (I/M), nonattainment new source review (NSR), contingency 
measures, clean fuel fleet program, vehicle miles travelled offset demonstration, and major 
source fee program.  
b. Air Quality Standards, Designations and Emission Budgets revisions to satisfy the transportation 
conformity requirements of Section 176(c) of the C lean Air Act and include MVEB in the Severe 
SIP. 
c. Regulation Number 7 revisions including clean up and responding to EPA concerns with adopted 
SIP requirements and reporting.  
d. Regulation Number 21  revisions to respond  to EPA concerns with adopted SIP requirements and 
reporting . 
e. Regulation Number 25  revisions to respond  to EPA concerns with adopted SIP requirements and 
reporting . 
f. Regulation Number 26  revisions to include requirements to  include provisions that require the 
implementation of RACT for major sources of VOC or NOx in the DMNFR, and to respond to 
other EPA concerns with adopted SIP provisions and reporting . 
  2 (2) State -Only Restrictions  That Will  Reduce Ozone Precursors, GHG, and Otherwise Improve Public 
Health and Welfare:  
a. Regulation Number 7 revisions for oil and gas drilling and pre -production operations.  The scope 
of this element of the rulemaking is limited to operations located in areas in nonattainment for 
the ozone NAAQS (t he 8-hour Ozone Control Area and Northern Weld County).  These revisions 
are not being proposed for inclusion in the SIP. However, the Commission may consider 
whether to include these provisions in the SIP as part of this rulemaking process.  
b. Regulation Numb er 26 requirements to emissions from stationary combustion engines.  The 
scope of this element of the  rulemaking  is limited , and will not extend  to engines in service 
(i.e. existing engines) of the type and size that are not already within the scope of the 
Division’s proposal.  
 
All required documents for this rulemaking can be found on the Commission website at: 
https://cdphe.colorado.gov/aqcc  
 
PUBLIC COMMENT SESSION 
DATE:  December 12, 2023 
TIME:  4:30 p.m. to 7:30 p.m. 
PLACE:  The session  will be held online only; there will be no in- person participation. Details related 
to participation and registration can be found at: https://cdphe.colorado.gov/aqcc  
NOTE:  The p ublic comment session may end early if all commenters that are registered and in 
attendance before 6 :30 have had an opportunity to speak prior to 7 :30. 
 
PARTY TESTIMONY & DELIBERATIONS 
DATE:  December 1 2-15, 2023 
TIME:  To begin at 9:00 a.m. on Dec 12, 2023  
PLACE:  The hearing will be held in a hybrid fashion both in- person and via Zoom. Parties to 
rulemaking hearings are encouraged to participate in -person. Details related to 
participation and registration can be found at: https://cdphe.colorado.gov/aqcc  
 IMPORTANT:  As Colorado begins to re -open from COVID -19, the Commission may reestablish conducting 
meetings at the Colorado Department of Public Health and Environment in its entirety or structured as 
a hybrid meeting. Any such changes will be noticed on the Commission’s website at: 
https://cdphe.colorado.gov/aqcc
 
 The hearing may be continued at such places and time as the Commission may announce. Any such 
changes w ill be noticed on the Commission’s website. Interested parties may contact the Commission 
Office at cdphe.aqcc -comments@state.co.us
 to confirm meeting details.  
 
PUBLIC COMMENT:  
The Commission encourage s input from the public, either orally during the public comment session or 
in writing prior to the hearing. However, oral public comment will generally not be permitted by persons who offer comment on behalf of an entity that is a party. Those persons may , however, submit 
written public comment.   
Instructions for registering to provide oral public comment will be posted in the agenda on the 
Commission’s website at https://cdphe.colorado.gov/aqcc
 on December 1, 2023.  
In order for Commissioners to have the opportunity to review the information within the comments you 
provide, written comments should be submitted no later than November 28, 2023 by emailing 
cdphe.aqcc- comments@state.co.us  or mailing to:  
 
Colorado Air Quality Control Commission  
Colorado Department of Public Health and Environment 
4300 Cherry Creek Drive South, EDO -AQCC- A5 
Denver, Colorado 80246   3  
IMPORTANT DATES AND DEADLINES: 
 
PROCESS DESCRIPTIO N DUE DATE & TIME  
Request for Party Status  October 12 , 2023 by 5:00 p.m.  
Status Conference  October 16 , 2023  at 8:30 a.m.  
Alternate Proposal  October 30 , 2023 by 5:00 p.m.  
 
Prehearing Statement  October 30 , 2023 by 5:00 p.m.  
 
Prehearing Conference  Novemb er 6, 2023  at 2:00 p.m. 
Rebuttal Statement  November 1 6, 2023 by 12:00 p.m.  
 
Written Public Comments  November 2 8, 2023 by 5:00 p.m.  
 
Submittals for this hearing should be emailed to cdphe.aqcc -comment s@state.co.us  unless an 
exception is granted pursuant to Subsection III.I.3. of the Commissions Procedural Rules.  
 
REQUEST FOR PARTY STATUS: 
A request for party status must:  
 
1) identify the applicant (this could be a company and/or contact name);  
2) provide t he name, address, telephone and email address of the applicant’s representative or 
counsel; and  
3) briefly summarize what, if any, policy, factual, and legal issues the applicant has with the 
proposal(s) as of the time of filing the application.  
 In additio n, requests for party status should indicate whether the applicant intends to file an alternate 
proposal and, if so, briefly describe the scope and nature of the alternate proposal.   
The request for party status must be electronically mailed to:  
 
• Air Qual ity Control Commission staff: theresa.martin@state.co.us
 
• Air Quality Control Commission attorney: robyn.wille@coag.gov  
• Air Pollution Control Division staff: leah.martland@state.co.us  
• Air Pollution Control Division attorney: laura.mehew@coag.gov  
• Air Pollution Control Division attorney: rylie.slaybaugh@coag.gov  
 Requests received beyond the stated deadline shall only be considered upon a written motion for good 
cause shown. The Commission reserves the right to deny party status to anyone that does not comply 
with the Commission’s Procedural Rules.  
  4 STATUS CONFERENCE:  
Attendance at the status conference is mandatory for anyone who has requested party status, though 
each party need only have one representative present. The status conference is intended to ascertain 
and discuss the issues involved, and to ensure that parties are making all necessary efforts to discuss 
and resolve such issues prior to the submission of prehearing statements. Following the status 
conference, party status will be confirmed and a party list will be gener ated and distributed. The 
status conference will be held virtually via video conference. A registration link will be provided by the 
Commission’s office prior to the status conference. Note that if the Hearing Officer deems the status 
conference unnecessar y, the status conference may be cancelled.   
 
ALTERNATE PROPOSAL:  
Alternate proposals will be considered by the Commission “only if the subject matter of the alternative proposal is consistent with and fits within the scope of the notice.” 5 CCR §1001-1, Section V.E.4.b . 
The submission of redlined language is not automatically considered an alternate proposal. Whether specific redlines rise to the level of an alternate proposal is determined on a case -by-case basis, taking 
into consideration many factors, including the impact of those redlines on the Division’s proposal. 
Parties submitting redlines that they do not believe should be considered alternate proposals are 
encouraged to provide information demonstrating that the redlines simply delete, clarify, or  elaborate 
on the Division’s proposal.  
 
The submittal of an alternate proposal must be accompanied by a separate electronic copy of the 
alternate proposed rule and statement of basis and purpose language and all other associated 
documents as required by t he Commission’s Procedural Rules, including an economic impact analysis. 
Alternate proposals and associated exhibits must be emailed to all persons listed on the party status 
list or otherwise provided through an approved method of electronic transmission.  Objections to the 
submission of redlines that are not identified as alternate proposals and accompanied by the required 
information for alternate proposals under the Commission’s Procedural Rules must be made by motion 
in writing prior to the Prehearing C onference.  
 
PREHEARING STATEMENTS:  
Each party must submit a prehearing statement. Exhibits to a prehearing statement must be submitted in a separate electronic transmission. Prehearing statements and associated exhibits must be emailed 
to all persons liste d on the party status list or otherwise provided through an approved method of 
electronic transmission. Prehearing statements must contain all the necessary elements described in subsection V.E.6.c of the Commission’s Procedural Rules (5 CCR § 1001- 1). The Hearing Officer may 
prescribe limitations on prehearing statements, such as page limits.  
 
PREHEARING CONFERENCE:  
Attendance at the prehearing conference is mandatory for all parties to this hearing, though each party 
need only have one representative present. The prehearing conference will be held virtually, and 
registration information will be provided by the Commission’s office prior to the prehearing 
conference.  
 
REBUTTAL STATEMENTS:  
Rebuttal statements may be submitted by the Division and any party to  the hearing to respond to issues 
and arguments identified in prehearing statements. Rebuttal statements may not raise any issues, or be accompanied by alternate proposals, that could have been raised in the party’s prehearing statement. 
Rebuttal statements and associated exhibits must be emailed to all persons listed on the party status 
list or otherwise provided through an approved method of electronic transmission. The filing of 
rebuttal statements is optional.  
 
DELIBERATION AND FINAL ACTION:  
The Commission intends to deliberate and take final action on the proposed changes to these Regulations at the conclusion of the testimony.  
  5 STATUTORY AUTHORITY FOR THE COMMISSION'S ACTIONS:  
General Authority : 
The Colorado Air Pollution Prevention and Control Act, S ection 25 -7-105(1) directs the Commission to 
promulgate such rules and regulations as are consistent with the legislative declaration set forth in 
Section 25 -7-102 and are necessary for the proper implementation and administration of Article 7. 
Section 25 -7-105(1)(b) directs the Commission to promulgate emission control regulations in 
accordance with Section 25 -7-109. 
 Sections 109(1)(a), (2), and (3) authorize the Commission  to promulgate regulations requiring effective 
practical air pollution controls for  significant sources and categories of sources and emission control 
regulations pertaining to nitrogen oxides and hydrocarbons. Section 109(10) also directs reductions in 
emissions from oil and gas activities, including NOx and hydrocarbons.  
 Section 25 -7-105(12) authorizes the Commission to promulgate regulations necessary to implement the 
provisions of the emission notice, construction permit, and Title V programs. Section 25 -7-106(1)(c) 
authorizes the Commission to promulgate emission control regulations applicable to the entire state, 
specified areas or zones, or when a specified class of pollution is present. Section 25 -7-106(6) further 
authorizes the Commission to require owners and operators of any air pollution source to monitor, 
record, and report i nformation . 
 
Specific Authority : 
As it relates to the SIP revisions, Section 25 -7-105(1)(a), Sections 25-7-201 through 25 -7-206, Section 
25-7-210, Section 25-7-301, and Section 25-7-302, direct the Commission to adopt and revise, as 
necessary, the SIP  to assure attainment and maintenance of national ambient air quality standards and 
prevent significant deterioration of air quality in conformance with the Federal and Colorado Acts. The 
authority to establish emissions budgets and to establish criteria for tr ansportation conformity 
determinations is included in the general authority to adopt a SIP are set out in Section 25 -7-105(1), 
C.R.S. 
 
As it relates to the Division’s proposal for Regulation Number 7, Section 25 -7-105(1)(e) directs the 
Commission to reduce  GHG, reducing pollution statewide and in disproportionately impacted 
communities. This statute requires specific GHG reductions from sources in the industrial and 
manufacturing sectors and the oil and gas sector, which include oil and gas preproduction activities. 
The Environmental Justice Act also directed the Division to protect disproportionately impacted 
communities from the impacts of pollution from, among other things,  oil and gas operations.  
 As it relates to the Division’s proposal for GHG emission  fees, House Bill 21 -1266 amended Section 25 -7-
114.7 to specifically direct the Commission to set these fees.  
 
The rulemaking hearing will be conducted in accordance with Sections 24-4-103 and 25 -7-110, 25 -7-
110.5 and 25- 7-110.8 C.R.S., as applicable and amended, the Commission’s Procedural Rules, all other 
applicable rules and regulations, and as otherwise stated in this notice. This list of statutory authority is not intended as an exhaustive list of the Commission’s statutory authority to act in this mat ter. 
 
Dated this 27th day of September 2023 at Denver, Colorado  
 
Colorado Air Quality Control Commission  
 
 
 
 
Jojo La, Administrator   6 DEPARTMENT OF PUBLIC HEALTH AND ENVIRONMENT  
Air Quality Control Commission 
REGULATION NUMBER 26  
Control of Emissions from Engines and Major Stationary Sources  
5 CCR 1001- 30 
[Editor’s Notes follow the text of the rules at the end of this CCR Document.]  
____ _____________________________________________________________________  
Outline of Regulation  
PART  A Applicability and General Provisions  
I. General Provisions  
Appendix A  Colorado Ozone Nonattainment or Attainment Maintenance Areas  
PART  B Combustion Equipment and Major Source RACT  
I. Control of Emissions from Engines  
II. Control of Emissions from Stationary and Portable Combustion Equipment in the 8- Hour 
Ozone Control Area  
III. Control of Emissions from Specific Major Sources of VOC and/or NOx in the 8- Hour 
Ozone Control Area  
IV. Control of Emissions from Breweries in the 8- hour Ozone Control Area  
V. Control of Emissions from Foam Manufacturing in the 8- hour Ozone Control Area  
VI. Control of Emissions from Bakeries in the 8- hour Ozone Control Area  
VII. Control  of Emissions from Poultry Waste Processing in the 8- hour Ozone Control Area  
VIII. Control of Emissions from Industrial Waste Facilities in the 8- hour Ozone Control Area  
PART  C Statements of Basis, Specific Statutory Authority and Purpose  
_________________________________________________________________________  
Pursuant to Colorado Revised Statutes §Section  24-4-103 (12.5), materials incorporated by reference are 
available for public inspection during normal business hours, or copies may be obtained at a re asonable 
cost from the Air Quality Control Commission (the Commission), 4300 Cherry Creek Drive South, Denver, 
Colorado 80246- 1530. The material incorporated by reference is also available through the United States 
Government Printing Office, online at www.govinfo.gov . Materials incorporated by reference are those 
editions in existence as of the date indicated and do not include any later amendments.  
PART A  General Provisions   7 I. General Provisions  
>>>>>>> 
I.C. New Sour ces 
All new sources shall utilize controls representing RACT, pursuant to applicable provisions in 
Regulation Number 7, Number 24, Number 25, Number 26 and Regulation Number 3, Part B, 
Section III.D., upon commencement of operation.  
>>>>>>> PART B Combusti on Equipment and Major Source RACT  
I. Control of Emissions from Engines  
>>>>>>> 
I.D. Control of emissions from new, modified, existing, and relocated natural gas fired reciprocating 
internal combustion engines.  
>>>>>>> 
I.D.5.  (State Only) Additional Requir ements for Natural Gas Fired Reciprocating Internal 
Combustion Engines  
I.D.5.a.  Applicability  
I.D.5.a.(i)  This Section I.D.5. applies to stationary natural gas fired 
reciprocating internal combustion engines state -wide with a 
manufacturer's design rate greater than or equal to 1000 horsepower.  
I.D.5.a.(i)(A)  For purposes of this Section I.D.5., modified means any 
physical change to the engine or change in method of 
operation that results in an increase in the emission rate of any air pollutant, and does not  include any physical or 
operational changes excluded by 40 C.F.R. 60.14(e).  
I.D.5.a.(i)(B)  For purposes of this Section I.D.5., placed in service means the bringing of an engine on- site for use. The 
placed in service date is the date the engine begins to 
operate. The following is not considered placed in 
service: (1) moving an engine subject to an Alternative 
Company -Wide Compliance Plan to another site with the 
same owner or operator; (2) for engines in service on or 
before November 14, 2020, replacement under an 
authorized alternative operating scenario.  
I.D.5.a.(i)(C)  For purposes of this Section I.D.5., relocated means the bringing of an engine into the 8- Hour Ozone Control 
Area from outside the 8 -Hour Ozone Control Area or the 
bringing of an engine into the State of Colorado from outside the State of Colorado. The relocation date is the 
date the subject engine begins to operate.   8 I.D.5.a.(ii)  Exemptions.  
I.D.5.a.(ii)(A)  Engines that burn less than 100 MMBtu per year of 
natural gas on a rolling -12-month basis are not subject 
to Sections I.D.5.b., I.D.5.d., I.D.5.e., I.D.5.f.(i) -(iii) and 
(v)-(vi), or I.D.5.g.  
I.D.5.a.(ii)(B)  Non-road engines, as defined in Regulation Number 3, 
Part A, Section I.B.3 61 are not subject to this Section 
I.D.5.  
I.D.5.a.(ii)(C)  Any emergency power generator exempt from APEN or construction permit requirements pursuant to Regulation 
Number 3, Parts A or B are not subject to this Section 
I.D.5.  
I.D.5.a.(ii)(D)  Emergency power generators that operate less than 250 hours per year on a rolling- 12-month basis are not 
subject to Sections I.D.5.b., I.D.5.d., I.D.5.e., I.D.5.f.(i) -
(iii) and (v) -(vi), or I.D.5.g.  
I.D.5.b.  Emission Standards for Engines Subject to Section I.D.5.a.  
I.D.5.b.(i)  The owner or operator of any stationary natural g as fired 
reciprocating internal combustion engine that is placed in service, modified, or relocated after November 14, 2020, must 
comply with the emission standards in Table 2 upon placement 
in service, modification, or relocation.  
I.D.5.b.(ii)  The owner or operator of any stationary natural gas fired 
reciprocating internal combustion engine not subject to Section 
I.D.5.b.(i) must comply with the emission standards in Table 2 in 
accordance with the timing set forth Section I.D.5.b.(v).  
 
TABLE 2  
Engine Type  Emission Standards (g/hp -hr) 
NOx CO VOC  
4-Stroke Lean Burn engines in service on or before November 
14, 2020, (unless subject to a more stringent emission 
standard under Section I.D.3.b, above)  1.2 2.0 0.7 
Rich Burn engines in service on or before November 14, 2020  0.8 2.0 0.7 
4-Stroke Lean Burn engines placed in service, modified, or 
relocated after November 14, 2020  0.7 2.0 0.7 
Rich Burn engines placed in service, modified, or relocated 
after November 14, 2020  0.5 2.0 0.7 
4-Stroke Lean Burn engines placed in service, modified, or 
relocated after January 30, 2024  0.5 2.0 0.7 
Rich Burn engines placed in service, modified, or relocated 0.3 2.0 0.7  9 after January 30, 2024  
2-Stroke Lean Burn engines  3.0 2.0 0.7 
 
>>>>>>> 
I.D.6.  (State Only) Additional Requirements for Internal Combustion Engines  
I.D.6.a.  Applicability  
I.D.6.a.(i)  This Section I.D.6. applies to stationary rich burn natural gas 
fired reciprocating internal combustion engines state -wide with a 
manufacturer's design rate greater than or equ al to 100 
horsepower but less than 1000 horsepower and lean burn 
natural gas fired reciprocating internal combustion engines state-
wide with a manufacturer's design rate greater than or equal to 
250 horsepower but less than 1000 horsepower.  
I.D.6.a.(ii)  This Section I.D.6. applies to stationary diesel or dual -fuel fired 
internal combustion engines state -wide with a manufacturer's 
design rate greater than or equal to 500 horsepower.  
I.D.6.a.(iii)  For purposes of this Section I.D.6., modified means any physic al 
change to the engine or change in method of operation that 
results in an increase in the emission rate of any air pollutant, 
and does not include any physical or operational changes 
excluded by 40 C.F.R. 60.14(e).  
I.D.6.a.(iv)  For purposes of this Secti on I.D.6., placed in service means the 
bringing of an engine on- site for use. The placed in service date 
is the date the engine begins to operate. For engines in service 
on or before January 30, 2024, replacement under an authorized 
alternative operating s cenario is not considered placed in 
service.  
I.D.6.a.(v)  For purposes of this Section I.D.6., relocated means the bringing 
of an engine into the 8- hour ozone control area from outside the 
8-hour ozone control area or the bringing of an engine into the 
State of Colorado from outside the State of Colorado. The 
relocation date is the date the subject engine begins to operate.  
I.D.6.a.(vi)  Exemptions.  
I.D.6.a.(vi)(A)  Engines that burn less than 100 MMBtu per year of 
natural gas on a rolling -12-month basis are not subject 
to Sections I.D.6.a. through I.D.6. d, or I.D.6. f. 
I.D.6.a.(vi)(B)  Non-road engines, as defined in Regulation Number 3, 
Part A, Section I.B.36  are not subject to this Section 
I.D.6.  
I.D.6.a.(vi)(C)  Any emergency power generator exempt from APEN or 
construction permit requirements pursuant to Regulation  10 Number 3, Parts A or B are not subject to this Section 
I.D.6.  
I.D.6.a.(vi)(D)  Emergency power generators that operate less than 250 
hours per year on a rolling- 12-month basis are not 
subject to Sec tions I.D.6.a. through I.D.6. d, or I.D.6. f. 
I.D.6.a.(vii)  Owners and operators of natural gas -fired engines less than 100 
horsepower are subject to reporting requirements in Section 
I.D.6.f.(ii).  
I.D.6.b.  Emission Standards for Engines Subject to Section I .D.6.a.  
I.D.6.b.(i)  The owner or operator of any stationary natural gas -fired 
reciprocating internal combustion engine that is placed in 
service, modified, or relocated after January 30, 2024, must 
comply with the emission standards in Table 5 upon placement 
in service, modification, or relocation.  
I.D.6.b.(ii)  The owner or operator of any stationary natural gas -fired 
reciprocating internal combustion engine not subject to Section 
I.D.6.b.(i) must comply with the emission standards in Table 5 in 
accordance with the timing set forth Section I.D.6.b.(v).  
 
TABLE 5  
Engine Type  Emission Standards  
NOx (g/hp -hr) 
Lean Burn and Rich Burn engines in service on or before 
January 30, 2024  0.5 
Lean Burn engines placed in service, modified, or relocated 
after January  30, 2024  0.5 
Rich Burn engines placed in service, modified, or relocated 
after January  30, 2024  0.3 
 
I.D.6.b.(iii)  The owner or operator of any stationary diesel or dual -fuel 
internal combustion engine that is placed in service, modified, or 
relocated after January 30, 2024, must achieve or exceed EPA 
Tier IV standards for NOx  upon placement in service, 
modification, or relocation.  
I.D.6.b.(iv)  The owner or operator of any stationary diesel or dual -fuel 
internal combustion engine not subject to Section I.D.6.b.(iii) 
must achieve or exceed EPA Tier IV standards for NOx in 
accordance with the timing set forth Section I.D.6.b. (vi). 
I.D.6.b.(v)  Permit Modification.   11 I.D.6.b.(v)(A)  An engine in service on or before January 30, 2024 that 
requires only a modific ation of an existing permit to meet 
the emission standards in this Section I.D.6.b. must 
submit a complete permit application containing the 
necessary limitations no later than May 1, 2024.  
I.D.6.b.(v)(B)  For any engine not subject to Section I.D.6.b.(v)(A ), 
owners and operators must modify existing permits to 
reflect the emission standards or other operating 
conditions necessary to achieve compliance with Table 
5. Complete permit applications must be submitted to 
the Division at least 365 days prior to the date 
established in Section I.D.6.b.(v i) for that engine.  
I.D.6.b.(vi)  Compliance deadlines for engines subject to Sections  I.D.6.b.(ii)  
or I.D.6.b.(iv) . 
I.D.6.b.(v i)(A) Engines that comply with the emission standards on or 
before January 30, 2024, or are subject to Section 
I.D.6.b.(v)(A) must meet the emission standards in Table 
5 by May 1, 2025.  
I.D.6.b.(v i)(B) Engines not subject to Section I.D.6.b.(v)(A) must meet 
the emission standards in Table 5 in accordance with the 
timing set forth in Table 6.  
 
TABLE 6  
Location of Subject 
Engines by Owner or 
Operator  Compliance Deadlines  
May 1, 2025  May 1, 2026  May 1, 2027  May 1, 2028  May 1, 2029  
Percent (%) of engines that must comply with Table 5 limits  
Inside, or inside and 
outside, the 8- Hour 
Ozone Contr ol Area  At least 34% 
of engines 
inside the 8-
Hour Ozone 
Control Area  At least 67% of 
engines inside the 
8-Hour Ozone 
Control Area; and 
at least 25% of 
engines outside 
the 8-Hour Ozone 
Control Area  100% of 
engines in the 
8-Hour Ozone 
Control Area; 
and at le ast 
50% of engines 
outside the 8-
Hour Ozone 
Control Area  At least 75% 
of engines 
outside the 
8-Hour 
Ozone 
Control Area  100% of all 
engines  
Outside the 8- Hour 
Ozone Control Area only  At least 20%  At least 40%  At least 60%  At least 80%  100%  
 
I.D.6.b.(vii)  If an owner or operator replaces an engine subject to an 
emission standard under this Section I.D.6.b. with a different 
stationary engine under an alternative operating scenario 
pursuant to an existing Division issued permit, the replacement  12 engine must, meet the same emission standard as the engine 
being replaced.  
I.D.6.c.  Performance Testing  
I.D.6.c.(i)  Engines subject to this Section I.D.6. must conduct a 
performance test consistent with the following requirements . 
I.D.6.c.(i)(A)  The owner or operator of an engine subject to Section 
I.D.6.b.(ii) must conduct a performance test fo r NOx  by 
May 1, 2025.  
I.D.6.c.(i)(B)  The owner or operator of an engine placed in service, 
modified, relocated or replaced after January 30, 2023 , 
must conduct a performance tes t within 12 months of the 
date the engine is placed in service, modified, relocated 
or replaced.  
I.D.6.c.(i)(C)  The following engines are exempt from the requirements 
of this Section I.D.6.c . 
I.D.6.c.(i)(C)(1)  Engines subject to the performance testing 
requirements of 40 C.F.R. Part 60, Subpart JJJJ 
(July 1, 2023)  or 40 C.F.R. Part 60, Subpart IIII 
(July 1, 2023) . 
I.D.6.c.(i)(C)(2)  Engines subject to at least semi -annual portable 
analyzer testing or ongoing performance testing 
in a permit issued on or befor e January 30, 
2024.  
I.D.6.c.(i)(D)  A performance test conducted in accordance with 40 
C.F.R. §60.4244 (July 1, 2023) or 40 C.F.R. §60.4212 – 
60.4213 (July 1, 2023) between January 1, 2023 and 
May 1, 2024,  will satisfy the initial performance testing 
requir ements in Section I.D.6.c.(i)(A).  
I.D.6.c.(ii)  Performance tests must be conducted in accordance with the 
applicable reference test methods of 40 C.F.R. Part 60, 
Appendix A (July 1, 2023), and a test protocol submitted to the 
Division for review at least t hirty (30) days prior to testing and in 
accordance with AQCC Common Provisions Regulation Section 
II.C. 
I.D.6.c.(iii)  Tuning of an engine prior to the performance test required by this 
Section I.D.6.c. is not a violation of this rule. However, 
readjustment  of an engine set point following the performance 
test that would negatively impact the performance of the engine 
(i.e., result in increased emissions above applicable permit limits) 
is a violation of this rule.  
I.D.6.d.  Monitoring. Except as provided in S ection I.D.6.a.(vi), owners or operators of an 
engine subject to Section I.D.6.a.  must:   13 I.D.6.d.(i) Beginning on May 1, 2025, conduct annual portable analyzer 
monitoring for NOx. At least six calendar months  must separate 
the annual tests.  
I.D.6.d.(i)(A)  If the engine is operated for less than 200 hours in any 
12-month period, then the portable analyzer monitoring 
need not occur during that annual period (i.e. , the engine 
does not need to be started for the sole purpose of 
portable monitoring).  
I.D.6.d.(i) (B) All portable analyzer testing required by this section 
must be conducted using the Division’s Portable 
Analyzer Monitoring Protocol (version: March 2006).  
I.D.6.d.(i)(C)  Tuning of an engine prior to annual monitoring events 
required by this Section I.D .6.d.(i) is not a violation of 
this rule. However, readjustment of an engine set point 
following the monitoring event that would negatively 
impact the performance (i.e. , result in increased 
emissions above applicable permit limits) of the engine 
is a viola tion of this rule.  
I.D.6.d.(i)(D)  A performance test conducted pursuant to Section 
I.D.6.c., 40 C.F.R. Part 60, JJJJ, IIII, or a permit 
requirement may take the place of the next required 
annual portable analyzer test required by this section.  
I.D.6.d.(i)( E) An engine subject to at least annual portable analyzer 
testing requirements in an existing permit issued by the 
Division can comply with this Section I.D.6.d.(i) by 
complying with the testing requirements in the permit.  
I.D.6.d.(ii)  Beginning May 1, 2024, if a catalyst is used to reduce emissions:  
I.D.6.d.(ii)(A)  Monitor the inlet temperature to the catalyst daily and 
conduct maintenance if the temperature is not within 
applicable limits.  
I.D.6.d.(ii)(B)  Measure the pressure drop across the catalyst mont hly 
and conduct maintenance if the pressure drop is greater 
than 2 inches outside the baseline value established 
after each annual portable analyzer monitoring.  
I.D.6.d.(ii)(C)  Engines that are subject to catalyst temperatures and 
catalyst pressure drop mo nitoring requirements in an 
existing permit issued by the Division or 40 C.F.R. Part 
63, Subpart ZZZZ (July 1, 2023) satisfy the monitoring 
requirements of this Section I.D.6.d.(ii).  
I.D.6.d.(iii)  Beginning May 1, 2024 or the date the engine is placed in 
service, modified, relocated or replaced (if later), install (if not 
already  installed) and operate an hour meter or Division 
approved alternate method to continuously track the hours of 
operation of the subject engine.   14 I.D.6.d.(iv)  Conduct the following i nspections and adjustments at least 
annually, unless otherwise specified, beginning in 2025.   
I.D.6. d.(iv)(A)  Change oil and filters as necessary; and,  
I.D.6.d.(iv)(B)  Inspect air cleaners, fuel filters, hoses, and belts and 
clean or replace as necessary; and, 
I.D.6.d.(iv)(C)  Inspect spark plugs and replace as necessary; or,  
I.D.6.d.(iv)(D)  Conduct a combustion process adjustment according to 
the manufacturer recommended procedures and 
schedule. Alternatively, the owner or operator may rely 
on a combustion process adjustment conducted in 
accordance with requirements and schedules of a New 
Source Performance Standard in 40 CFR Part 60 (July 
1, 2023) or National Emission Standard for Hazardous 
Air Pollutants in 40 CFR Part 63 (July 1, 2023) 
conducted during the same annual period to satisfy the 
annual combustion process adjustment requirement of 
this Section I.D.6.d.(iv)(D) for that 12 -month period.  
I.D.6.e.  Recordkeeping. The following records must be kept for a period of five years and 
made available to the D ivision upon request.  
I.D.6.e.(i)  Records of performance tests conducted pursuant to Section 
I.D.6.c ., including I.D.6.c.(i)(D), including the date, engine 
settings on the date of the test, and documentation of the 
methods and results of the testing.  
I.D.6 .e.(ii)  Records of semi -annual portable analyzer monitoring, including 
the date, engine settings on the date of the monitoring, and 
documentation of the results of the monitoring. These records 
must include any demonstration that no annual portable analyzer 
monitoring was required as provided under Section s 
I.D.6.d.(i)(D) or I.D.6.d.(i)(E), if applicable.  
I.D.6.e.(iii)  Records of catalyst monitoring required by Section I.D.6.d.(ii) 
and any actions taken to address monitored values outside the 
temperature or  pressure drop parameters, including the date and 
a description of actions taken.  
I.D.6.e.(iv)  If claiming an exemption under Section I.D.6.a.(vi), records 
demonstrating that fuel combustion was less than 100 MMBtu 
per year or hours of operation are less than 250 hours per year.  
I.D.6.e.(v)  Hours of operation as recorded by the hour meter  or alternative 
device approved by the Division continuously tracking hours as 
required by Section I.D.6.d.(iii) , at least on a calendar month 
basis.  
I.D.6.e.(vi)  Record s of tuning, adjustments, or other combustion process 
adjustments required under Section I.D.6.d.(iv), including:  
I.D.6.e.(vi)(A)  The date of the adjustment.   15 I.D.6.e.(vi)(B)  A description of any corrective action taken.  
I.D.6.e.(vi)(C)  If the owner or oper ator conducts the combustion 
process adjustment according to the manufacturer 
recommended procedures and schedule and the 
manufacturer specifies a combustion process 
adjustment on an operation time schedule, the hours of 
operation since the last combustion process adjustment 
and the procedures followed. The owner or operator 
must retain documentation of any relied upon 
manufacturer recommended procedures, specifications, 
and maintenance schedule for five years after the owner 
or operator ceases to rely upon it. 
I.D.6.e.(vi)(D)  If the owner or operator conducts the combustion 
process adjustment according to a New Source 
Performance Standard or National Emission Standard 
for Hazardous Air Pollutants, what standard applied and 
what procedures were followed.  
I.D.6.f. Reporting.  
I.D.6.f.(i)  Beginning on the date specified and by May 1 of each year 
thereafter, the owner or operator of each engine subject to this 
Section I.D.6. must submit the following information covering the 
preceding calendar year . 
I.D.6.f.(i)( A) Beginning May 1, 2024, a statement of the status of 
performance testing required under Section I.D.6.c ., and 
the date and results of that testing.  
II.D.6.f.(i)(B)  Beginning May 1, 2025, an identification of any engines 
placed in service, modified, reloc ated, or replaced, 
including AIRS number, serial number, location, engine 
configuration, and a certification as to whether the 
emission standards in Table 5 are met . 
I.D.6.f.(i)(C)  Beginning May 1, 2026, the date on which the 
monitoring required by Sections I.D.6.d.(iv) was 
performed.  
I.D.6.f.(i)(D)  Beginning May 1, 2026, the date that all required annual 
portable analyzer testing was performed under Section 
I.D.6.d.(i), and the results of that testing.  
I.D.6.f.(ii)  Owners and operators subject to I.D.6.a.( vii) must submit the 
following information on or before May 1, 2024.  
I.D.6.f.(ii)(A)  A identification of any engines less than 100 horsepower 
placed in service, modified, relocated, or replaced before 
January 30, 2024, including AIRS number, serial 
number,  location, and engine configuration.  
I.D.6.f.(ii)(B)  For each identified engine, the previous calendar year 
actual NOx emission rate expressed in g/hp- hr.  16 I.D.6.f.(ii)(C)  For each identified engine, the current permitted NOx 
emission rate expressed in g/hp- hr. 
 
II. Control of Emissions from Stationary and Portable Combustion Equipment in the 8 -Hour 
Ozone Control Area  or Northern Weld County  
II.A. Requirements for major sources of NOx  
II.A.1.  Applicability.  
II.A.1.a.  Except as provided in Section II.A.2., th e requirements of this Section II.  apply to 
owners and operators of any stationary combustion equipment that existed at a 
major source of NOx (greater than or equal to 100 tpy NOx) as of June 3, 2016, 
located in the 8- Hour Ozone Control Area.  
II.A.1.b.  Except as provided in Section II.A.2., the requirements of Section II. apply to 
owners and operators of any stationary combustion equipment that existed at a 
major source of NOx (greater than or equal to 50 tpy NOx) as of January 27, 
2020, located in the 8- Hour Ozone Control Area, that is not already subject as 
provided under Section II.A.1.a.  
II.A.1.c.  Except as provided in Section II.A.2., the requirements of Section II. apply to 
owners and operators of process heaters that existed at source that emits, or has 
the potential to emit, NOx emissions greater than or equal to 25 tpy NOx as of 
July 20, 2021, located in the 8- Hour Ozone Control Area, that is not already 
subject as provided under Sections II.A.1.a. or II.A.1.b.  
II.A.1.d.  Except as provided in Section II.A.2., the requirements of Section II. apply to 
owners and operators of any stationary combustion equipment that existed at a major source of NOx (greater than or equal to 25 tpy NOx) as of November 7, 
2022, located in the 8- Hour Ozone Control Area, that is not already subject as 
provided under Sections II.A.1.a. through II.A.1.c.  
II.A.1.e.  Except as provided in Sections II.A.2. or III.C., the requirements of Section II. apply to owners and operators of any stationary combustion equipment that 
existed at  a major source of NOx (greater than or equal to 100 tpy NOx) as of 
November 7, 2022, located in northern Weld County.  
II.A.2.  Exemptions. The following stationary combustion equipment are exempt from the emission limitation requirements of Section II.A.4. , the compliance demonstration 
requirements in Section II.A.5., and the related recordkeeping and reporting requirements of Sections II.A.7.a -e. and II.A.8, but these sources must maintain any and all records 
necessary to demonstrate that an exemption appl ies. These records must be maintained 
for a minimum of five years and made available to the Division upon request. Qualifying 
for an exemption in this section does not preclude the combustion process adjustment 
requirements of Section II.A.6., when require d by II.A.6.a.   
 Once stationary combustion equipment no longer qualifies for any exemption, the owner or operator must comply with the applicable requirements of this Section II.A. as expeditiously as practicable but no later than 36 months after any exem ption no longer 
applies. Additionally, once stationary combustion equipment that is not equipped with 
CEMS or CERMS no longer qualifies for any exemption, the owner or operator must 
conduct a performance test using EPA test methods within 180 days and noti fy the  17 Division of the results and whether emission controls will be required to comply with the 
emission limitations of Section II.A.4.  
II.A.2.a.  Any stationary combustion equipment whose utilization is less than:  
II.A.2.a.(i)  20% of its capacity factor on an annual average basis over a 3 -
year rolling period for boilers; or  
II.A.2.a.(ii)  10% of its capacity factor on an annual average basis over a 3 -
year rolling period for stationary combustion turbines and 
compression ignition reciprocating internal combustion engines.  
II.A.2.b.  An engine testing operation or process line.  
II.A.2.c.  Any gaseous fuel fired stationary combustion equipment used to control VOC 
emissions from a commercial or industrial process.  
II.A.2.d.  Any stationary combustion equipment with total uncontrolled actual emissions 
less than 5 tpy NOx on a calendar year basis.  
II.A.2.e.  Any natural gas -fired reciprocating internal combustion engines subject to a work 
practice or emission control requirement contained in this Regulation Number 26, 
Part B, Section I.A. or I.B. 
II.A.2.f.  Any stationary combustion equipment subject to a federally enforceable work 
practice or emission control requirement contained in this Regulation Number 26, 
Part B, Section s III.A. through III. C. or Regulation 23. 
II.A.3. Definitions  
II.A.3.a.   “Affected unit ” means any stationary combustion equipment that is 
subject to or becomes subject to an emission limitation in Section II.A.4.  
II.A.3.b.   “Boiler ” means an enclosed device using controlled flame combustion 
and havi ng the primary purpose of recovering thermal energy in the form 
of steam or hot water.  
II.A.3.c.   “Capacity factor ” means the ratio of the amount of fuel burned by an 
emissions unit in a calendar year to the amount of fuel it could have 
burned if it had operated at the designed heat input rating for 8,760 
hours during the calendar year. Alternatively, for electric generating 
units, capacity factor can mean the ratio of the unit’s actual annual 
electric output (expressed in MWe/hr) to the electric output the unit could 
have achieved if it operated at its nameplate capacity (or maximum 
observed hourly gross load (expressed in MWe/hr) if greater than the 
nameplate capacity) for 8,760 hours during the calendar year.  
II.A.3.d.   “Ceramic kiln ” means equipment used for the curing or firing of ceramic 
products or glaze on ceramic products. A kiln may operate continuously or by batch process.  
II.A.3.e.   “Continuous emission monitoring system ” (“CEMS” ) or “Continuous 
emission rate monitoring system ” (“CERMS ”) means the total equipment 
required to sample, condition (if applicable), analyze, and provide a written record of such emissions and/or emission rates, expressed on a  18 continuous basis in terms of an applicable emission limitation. Such 
equipment includes, but is not limited to, sample collection and 
calibration interfaces, pollutant analyzers, a diluent analyzer (oxygen or 
carbon dioxide), stack gas volumetric flow monitors (if appropriate for 
CERMS), and data recording and storage devices.  
II.A.3.f.   “Compression i gnition reciprocating internal combustion engine (RICE) ” 
means a type of stationary RICE that is liquid fuel -fired and not ignited 
with a spark plug or other sparking device.  
II.A.3.g.   “Digester gas ” means any gaseous byproduct of wastewater treatment 
typically formed through the anaerobic decomposition of organic waste 
materials and composed principally of methane and carbon dioxide.  
II.A.3.h.   “Duct burner ” means a device that combusts fuel and is placed in the 
exhaust duct from another source (e.g., stationary combustion turbine, 
internal combustion engine, or kiln) to allow the firing of additional fuel to 
heat the exhaust gases before the exhaust gases enter a heat recovery 
steam generating unit.  
II.A.3.i.   “Dryer”  means a device that is used to reduce or evaporate moisture 
content or remove organic contaminants.  
II.A.3.j.   “Furnace”  means an enclosed device that is an integral component of a 
manufacturing process and that uses thermal treatment to accomplish 
recovery of materials or energy.  
II.A.3.k.   “Gaseous fuel ” means natural gas, landfill gas, refinery fuel gas, digester 
gas, methane, ethane, propane, butane, or any gas stored as a liquid at 
high pressure such as liquefied petroleum gas.  
II.A.3.l.   “Glass melting furnace ” means an emissions unit co mprising a refractory 
vessel in which raw materials are charged, melted at high temperature, refined, and conditioned to produce molten glass.  
II.A.3.m.  “Kiln” means the equipment used to remove combined (chemically 
bound) water and/or gases from mineral m aterial through direct or 
indirect heating.  
II.A.3.n.   “Lightweight aggregate ” means the expanded, porous product from 
heating shales, clays, slates, slags, or other natural materials in a kiln.  
II.A.3.o.   “Liquid fuel ” means any fuel which is a liquid at standard conditions 
including but not limited to distillate oils, kerosene and jet fuel. Liquefied 
gaseous fuels are not liquid fuels.  
II.A.3.p.   “Process heater” means an enclosed device using controlled flame and a 
primary purpose to transfer heat indire ctly to a process material or to a 
heat transfer material for use in a process unit, instead of generating 
steam. Process heaters are devices in which the combustion gases do 
not come into direct contact with process materials.  
II.A.3.q.   “Reciprocating in ternal combustion engine”  means any reciprocating 
internal combustion engine which uses reciprocating motion to convert  19 heat energy into mechanical work and which is not used to propel a 
motor vehicle or a vehicle used solely for competition.  
II.A.3.r.   “Stationary combustion equipment ” means an emissions unit that 
combusts solid, liquid, or gaseous fuel, generally for the purposes of producing electricity, generating steam, or providing useful heat or 
energy for industrial, commercial, or institutional use. Stationary 
combustion equipment includes, but is not limited to, boilers, duct 
burners, engines, glass melting furnaces, kilns, process heaters, 
stationary combustion turbines, dryers, furnaces, and ceramic kilns.  
II.A.3.s.   “Stationary combustion turbine ” means a non- mobile, enclosed fossil or 
other fuel -fired device that is comprised of a compressor, a combustor 
and a turbine, and in which the flue gas resulting from the combustion of 
fuel in the combustor passes through the turbine, rotating the turbine. 
Stationary combustion turbines can be simple cycle or combined cycle and they may or may not include a duct burner.  
II.A.4.  Emission limitations.  
By October 1, 2021, or the applicable date in Section II.A.4.g. for process heaters, no owner or operator of stationary combustion equipment specified in Section II.A.1.a. may cause, allow, or 
permit NOx to be emitted in excess of the following emission limitations. When demonstrating 
compliance using continuous emissions monitoring pursuant to Section II.A.5.b.(i), the following emission limitations are on a 30- day rolling average basis, unless otherwise specified.  
By July 20, 2021, or the applicable date in Section II.A.4.g. for process heaters, no owner or 
operator of stationary combustion equipment specified in Section II.A.1.b. may cause, allow, or 
permit NOx to be emitted in excess of the following emission limitations. When demonstrating 
compliance using continuous emissions monitoring pursuant to Section II.A.5.b.(i), the following 
emission limitations ar e on a 30- day rolling average basis, unless otherwise specified.  
By May 1, 2022, or May 1 2023, as specified in Section II.A.4.g., no owner or operator of process 
heaters specified in Section II.A.1.c. may cause, allow, or permit NOx to be emitted in exces s of 
the following emission limitations. Compliance with the applicable emission limitations contained 
in Section II.A.4. must be determined according to the applicable methods contained in Sections 
II.A.5. When demonstrating compliance using continuous em issions monitoring pursuant to 
Section II.A.5.b.(i), the following emission limitations are on a 30 -day rolling average basis, unless 
otherwise specified.  
By May 1, 2024, or the applicable date in Section II.A.4.g. for process heaters, no owner or 
operator  of stationary combustion equipment specified in Sections II.A.1.d. or II.A.1.e. may cause, 
allow, or permit NOx to be emitted in excess of the following emission limitations. When demonstrating compliance using continuous emissions monitoring pursuant to Section II.A.5.b.(i), 
the following emission limitations are on a 30- day rolling average basis, unless otherwise 
specified.  
>>>>>>> 
II.A.4.f.  Landfill gas or biogas gas fired RICE.  
II.A.4.f.(i)  For landfill gas or biogas fired RICE with a maximum design power output equal to or greater than 500 horsepower, 1.52 
grams per brake horsepower -hour.  20 II.A.4.g.  Process heaters  
II.A.4.g.(i)  Except as specified in Section II.A.4.g.(ii), by May 1, 2022, 
process heaters must comply with the following NOx emission limits in Table 2.  
 
Table 2 – NOx limits for process heaters  
Heat input rate 
(MMBtu/hr)  Fuel type NOx emission limit 
(lb/MMBtu)  
> 5 and < 100  Natural gas  0.05 
> 5 Refinery fuel gas  0.1 
 
II.A.4.g.(ii)  Process heaters that require a permitting action or facil ity shut -
down to comply with the NOx emission limits in Table 2 must 
comply by May 31, 2023.  
II.A.4.g.(iii)  Process heaters subject under Section II.A.1.e. must comply with 
the NOx emission limits in Table 2 by May 1, 2024.  
II.A.5.  Compliance demonstration.  
II.A.5.a.  Compliance date 
II.A.5.a.(i)  By October 1, 2021, for stationary combustion equipment that 
existed at a major source of NOx (greater than or equal to 100 
tpy NOx) located in the 8- hour ozone control area as of June 3, 
2016, except for process heaters specified in Section II.A.4.g., 
the owner or operator of an affected unit must determine 
compliance with the applicable emission limitations contained in 
Section II.A.4. according to the applicable methods contained in this Section II.A.5.  
II.A.5.a.( ii) By July 20, 2021, for stationary combustion equipment specified in Section II.A.1.b., except for process heaters specified in Section II.A.4.g., the owner or operator of an affected unit must 
determine compliance with the applicable emission limitations 
contained in Section II.A.4. according to the applicable methods 
contained in Sections II.A.5.  
II.A.5.a.(iii)  By May 1, 2022, for process heaters specified in Section 
II.A.4.g.(i). or May 31, 2023, for process heaters specified in 
Section II.A.4.g.(ii), the owner or operator of an affected unit 
must determine compliance with the applicable emission 
limitations contained in Section II.A.4. according to the applicable 
methods contained in Sections II.A.5.  
II.A.5.a.(iv)  By May 1, 2024, for stationary combust ion equipment specified 
in Section II.A.1.d., except for process heaters specified in  21 Section II.A.4.g., the owner or operator of an affected unit must 
determine compliance with the applicable emission limitations 
contained in Section II.A.4. according to the applicable methods 
contained in Sections II.A.5.  
II.A.5.a.(v)  By May 1, 2024, for stationary combustion equipment specified in Section II.A.1.e., except for process heaters specified in 
Section II.A.4.g., the owner or operator of an affected unit must 
determine compliance with the applicable emission limitations 
contained in Section II.A.4. according to the applicable methods contained in Sections II.A.5.  
II.A.5.b.  Emissions monitoring requirements for major source RACT limits  
>>>>>>> 
II.A.5.b.(ii)  Initial and periodic performance testing  
II.A.5.b.(ii)(A)  An owner or operator of a stationary combustion turbine subject to 40 CFR Part 60, Subparts GG or KKKK 
(October 7, 2020) that has used and continues to use 
performance testing to demonstrate compliance with 
either Subpart GG or KKKK (October 7, 2020), as 
applicable, may use those performance testing 
procedures to demonstrate continued compliance with an applicable limitation contained in Section II.A.4.b., 
thereby satisfying the requirements of this Sec tion 
II.A.5.b.(ii).  
II.A.5.b.(ii)(B)  An owner or operator of a process heater subject to a NOx emission limit in Section II.A.4.g. must  
II.A.5.b.(ii)(B)(1)  For natural gas -fired and refinery gas -fired 
process heaters greater than or equal to 100 MMBtu/hr,  conduct an initial performance test in 
accordance with Sections II.A.5.b.(ii)(D)(1), 
II.A.5.b.(ii)(D)(4), and II.A.5.b.(ii)(E) by April 1, 
2022, or by November 30, 2023, for process 
heaters specified in Section II.A.4.g.(ii) , and 
conduct subsequent perfor mance tests in 
accordance with Sections II.A.5.b.(ii)(D)(1), 
II.A.5.b.(ii)(D)(4), and II.A.5.b.(ii)(E) every 2 
years thereafter.  
II.A.5.b.(ii)(B)(2)  For natural gas -fired process heaters greater 
than or equal to 50 MMBtu/hr and less than 100 MMBtu/hr,  cond uct an initial performance test in 
accordance with Sections II.A.5.b.(ii)(D)(1), 
II.A.5.b.(ii)(D)(4), and II.A.5.b.(ii)(E) by April 1, 
2022, or by November 30, 2023, for process 
heaters specified in Section II.A.4.g.(ii) , and 
comply with the combustion pro cess adjustment 
requirements in Section II.A.6. thereafter.   22 II.A.5.b.(ii)(B)(3)  For natural gas -fired process heaters greater 
than or equal to 5 MMBtu/hr and less than 50 
MMBtu/hr and refinery gas -fired process heaters 
greater than or equal to 5 MMBtu/hr and less 
than 100 MMBtu/hr,  comply with the combustion 
process adjustment requirements in Section 
II.A.6.  
II.A.5.b.(ii)(B)(4)  For a group of process heaters that vent to a 
common stack, the owner or operator may either 
assess compliance for the heaters indi vidually 
by performing a separate emission test of each 
heater in the duct leading from the heater to the 
common stack or may perform a single emission 
test in the common stack. The owner or operator 
must include in the test protocol for these units a 
definition of representative conditions for 
performance testing purposes.   
II.A.5.b.(ii)(B)(5)  For natural gas -fired process heaters subject 
under Sections II.A.1.d. or II.A.1.e. and greater than or equal to 50 MMBtu/hr and less than 100 MMBtu/hr,  conduct an i nitial performance test in 
accordance with Sections II.A.5.b.(ii)(D)(1), II.A.5.b.(ii)(D)(4), and II.A.5.b.(ii)(E) by April 1, 
2024, and comply with the combustion process 
adjustment requirements in Section II.A.6. thereafter.  
II.A.5.b.(ii)(B)(6)  Performan ce tests conducted in accordance with 
Sections II.A.5.b.(ii)(D)(1) through II.A.5.b.(ii)(D)(3) and II.A.5.b.(ii)(E) within three (3) years of the applicable performance testing 
date in Sections II.A.5.b.(ii)(B)(1) or 
II.A.5.b.(ii)(B)(2) will satisfy the in itial 
performance testing requirement.  
II.A.5.b.(ii)(B)(7)  As an alternative to the requirements in Sections II.A.5.b.(ii)(B)(1), II.A.4.b.(ii)(B)(2), 
II.A.5.b.(ii)(B)(4), and II.A.5.b.(ii)(B)(5), the 
owner or operator may install, operate, and 
maintain a NOx CEMS or CERMS in 
accordance with Sections II.A.5.b(i)(A)(1) through II.A.5.b.(i)(A)(4) to monitor compliance 
with the applicable emission limit.  
II.A.5.b.(ii)(C)  An owner or operator of a boiler subject to a NOx limit 
under Sections II.A.4.a.(v) or I I.A.4.a.(vi) , conduct an 
initial performance test in accordance with Sections 
II.A.5.b.(ii)(D)(1), II.A.5.b.(ii)(D)(4), and II.A.5.b.(ii)(E) by 
April 1, 2024, and comply with the combustion process 
adjustment requirements in Section II.A.6. thereafter . 
II.A.5.b.(ii)(D)  Except as otherwise provided for in Sections II.A.5.b.(ii)(A), II.A.5.b.(ii)(B), or II.A.5.b.(ii)(C), the owner or operator of an affected unit subject to a NOx emission  23 limitation contained in Sections II.A.4.a.(iv), II.A.4.b., or 
II.A.4.e. that is not equipped with NOx CEMS or 
CERMS, must conduct an initial performance test and 
subsequent performance tests every 2 years thereafter, 
according to the following requirements, as applicable, to 
determine the affected unit’s NOx emission rate for each 
fuel fired in the affected unit.   
II.A.5.b.(ii)(D )(1) A performance test is not required for a fuel used only for startup or for a fuel constituting less than 2% of the unit’s annual heat input, as 
determined at the end of each calendar year.  
II.A.5.b .(ii)(D)(2) Initial performance test must include a determination of the capacity load point of the 
unit’s maximum NOx emissions rate based on one 30 -minute test run at each capacity load 
point for which the unit is operated, other than for startup and shutdown, in the load ranges of 20 to 30%, 45 to 55%, and 70 to 100%. 
Subsequent performance tests must be 
performed within the capacity load range 
determined to result in the maximum NOx 
emissions rate.  
II.A.5.b.(ii)(D )(3) Performance tests must determine compliance 
with Section II.A.4. based on the average of 
three 60 -minute test runs performed at the 
capacity load deter mined in Section 
II.A.5.b.(ii)(D )(2). 
II.A.5.b.(ii)(D )(4) Initial performance test must be conducted at 
both high and low load capacity. If site 
operations do not allow testing at high and low 
loads, the initial performance test must be 
conducted at the highest achievable load that 
site conditions allow. The owner or operator 
must submit a summary of six months of 
operating performance with the test protocol 
supporting the testing load(s). Subsequent 
performance tests must be performed within the 
capacity load range determined to result in the 
maximum NOx emissions rate. Performance 
tests must determine compliance based on the average of three 60-minute test runs.  
II.A.5.b.(ii)(E)  The owner or operator of an affected unit subject to a 
NOx emission limitation contained in Section II.A.4. f. that 
is not equipped with NOx CEMS or CERMS, must 
conduct an initial performance test  by May 1, 2025 , and 
subsequent performance tests every 3 years thereafter, 
according to the requirements  in Sections 
II.A.5.b.(ii)(D)(1) through II.A.5.b.(ii)(D)(4) , as applicable, 
to determine the affected unit’s NOx emission rate for 
each fuel fired in the affected unit.  In lieu of subsequent 
triennial performance tests,  the owner or operator may   24 conduct semi -annual  portable analyzer monitoring for 
NOx conducted using the Division’s Portable Analyzer 
Monitoring Protocol (March 2006) . A performance test 
conducted on the engine in accordance with 40 C.F.R. 
Part 60 (July 1, 2023) between January 1, 2022, and 
April 30, 202 5, will satisfy the initial performance test 
requirement.  
II.A.5.b.(ii)( EF) All performance tests must be conducted in accordance 
with EPA test methods and a test  protocol submitted to 
the Division for review at least thirty (30) days prior to 
testing and in accordance with AQCC Common 
Provisions Regulation Section II.C.  
II.A.5.b.(iii)  For affected units’ subject to a production- based or output based 
emission limit  contained in Section II.A.4. (e.g. lb of NOx/ton of 
product), the owner or operator must install, operate, and 
maintain monitoring equipment for measuring and recording the 
affected unit’s production or output, on an hourly basis, in units consistent with the applicable emission limitation.  
II.A.5.b.(iv)  Where measuring fuel use is necessary to calculate an emission rate in the units of the applicable standard, fuel flowmeters must be installed, calibrated, maintained, and operated according to 
manufacturer’s instructions for measuring and recording heat 
input in terms of the applicable emission limitation. Alternatively, 
fuel flowmeters that meet the installation, certification, and 
quality assurance requirements of 40 CFR Part 75, Appendix D 
(July 19, 201 8) are acceptable for demonstrating compliance 
with this section. The installation of fuel -flowmeters is not 
required where emissions of NOx in terms of the applicable standard can be calculated in accordance with applicable provisions of EPA Method 19 (July 19, 2018) or where the 
standard is concentration based (e.g. parts per million dry 
volume corrected for oxygen).  
>>>>>>> 
II.A.7.  Recordkeeping. The following records must be kept for a period of five years and made 
available to the Division upon request : 
II.A.7.a.  The applicable emission limit and calculated heat input weighted emission limit for stationary combustion equipment demonstrating compliance for multiple fuels.  
II.A.7.b.  The 30 -day rolling average emission rate calculated on a daily basis for sources 
using CERMS to comply with Section II.A.  
II.A.7.c.  The type and amount of fuel used.  
II.A.7.d.  The stationary combustion equipment’s annual capacity factor on a calendar year 
basis.  
II.A.7.e.  All records generated to comply with the reporting requi rements contained in 
Section II.A.8.   25 II.A.7.f.  For stationary combustion equipment subject to the combustion process 
adjustment requirements in Section II.A.6., the following recordkeeping 
requirements apply:  
II.A.7.f.(i)  The owner or operator must create a record once every calendar 
year identifying the combustion equipment at the source subject 
to Section II.A. and including for each combustion equipment:  
II.A.7.f.(i)(A)  The date of the adjustment;  
II.A.7.f.(i)(B)  Whether the combustion process adjustment  under 
Sections II.A.6.b.(i) through II.A.6.b.(vi) was followed, 
and what procedures were performed;  
II.A.7.f.(i)(C)  Whether a combustion process adjustment under 
Sections II.A.6.c.(i). and II.A.6.c.(ii). was followed, what 
procedures were performed, and w hat New Source 
Performance or National  Emission Standard for 
Hazardous Air Pollutants applied, if any; and  
II.A.7.f.(i)(D)  A description of any corrective action taken.  
II.A.7.f.(i)(E)  If the owner or operator conducts the combustion 
process adjustment according to the manufacturer 
recommended procedures and schedule and the 
manufacturer specifies a combustion process adjustment on an operation time schedule, the hours of 
operation.  
II.A.7.f.(i)(F)  If multiple fuels are used, the type of fuel burned and 
heat input provided by each fuel.  
II.A.7.f.(ii)  The owner or operator must retain manufacturer recommended procedures, specifications, and maintenance schedule if utilized under Section II.A.6.c.(i). for the life of the equipment.  
II.A.7.f.(iii)  As an alternative to the requirements described in Section II.A.7.f.(i), the owner or operator may comply with applicable recordkeeping requirements related to combustion process 
adjustments conducted according to a New Source Performance 
Standard in 40 CFR Part 60 (July 1, 2022) or National Emission 
Standard for Hazardous Air Pollutants in 40 CFR Part 63 (July 1, 
2022).  
II.A.7.g.  All sources qualifying for an exemption under Section II.A.2. must maintain all 
records necessary to demonstrate that an exemption applies . 
II.A.7.h.  Records of semi -annual portable analyzer monitoring, including the date, engine 
settings on the date of the monitoring, and documentation of the results of the 
monitoring.  
II.A.8.  Reporting   26 II.A.8.a.  For affected units demonstrating compliance with Section II.A.4. using CEMS or 
CERMS in accordance with Section II.A.5.c.(i)(A), the owner or operator must 
submit to the Division the following information:  
II.A.8.a.(i)  Quarterly or semi -annual excess emissions reports no later than 
the 30th day fol lowing the end of each semi -annual or quarterly 
period, as applicable. Excess emissions means emissions that 
exceed the applicable limitations contained in Section II.A.4. 
Excess emission reports must include the information specified 
in 40 CFR Part 60, Section 60.7(c) (July 1, 2018).  
II.A.8.b.  For affected units demonstrating compliance with Section II.A.4 using performance testing pursuant to Section II.A.5.c.(ii)(C), the owner or operator 
must submit to the Division the following information:  
II.A.8.b.(i )  Performance test  or portabl e analyzer testing reports  within 60 
days  after completion of the performance test program  or 
portable analyzer testing. All performance test reports must 
determine compliance with the applicable emission limitations set by Se ction II.A.4.  
II.A.8.c.  Beginning in 2024, the owner or operator must submit periodic reports (e.g., 
deviation reports, compliance certifications) as required by the source’s operating 
permit.  
III. Control of Emissions from Specific Major Sources of VOC and/or NOx in the 8 -hour Ozone 
Control Area  
>>>>>>> 
III.D.  Golden Aluminum (123- 0089)  must submit a RACT analysis for the facility emission points  with 
actual  emissions equal to or greater than 2 tpy  VOC , except point 018,  to the Division no later 
than June  30, 2024. Approved RACT determinations will be addressed in the relevant source 
permit or through rule revisions, as appropriate.  
>>>>>>> 
V. Control of Emissions from Foam Manufacturing in the 8 -hour Ozone Control Area  
V.A. Requirements for Foam Product Manufacturing  
V.A.1.  Applicability  
V.A.1.a.   Except as provided in Section V.A.2., the requirements of Section V. 
apply to owners or operators of foam manufacturing operations that 
existed at a major source of VOC (greater than or equal to 50 tpy VOC) 
as of January 27, 2020, located in the 8- hour Ozone Control Area.  
V.A.1.b.   Except as provided in Section V.A.2., the requirements of Section V. 
apply to owners or operators of foam manufacturing operations that 
existed at a major source of VOC (greater than or equal to 25 tpy VOC) 
as of November 7, 2022, located in the 8- hour Ozone Control Area.  
V.A.2.  Exemptions   27 Any foam manufacturing operation that uses only non- VOC blowing agents is exempt from this 
Section V.A.  
V.A.3.  Definitions  
V.A.3.a.   “Blowing agent” means any liquid, gaseous or solid substance that alone 
or in conjunction with other substances is capable of producing a cellular 
(foam) structure in a polymeric material.  
V.A.3.b.   “Expandable polystyrene (EPS) beads” means polystyrene beads, particles, or  granules, usually less than one- twelfth inch in diameter, that 
are formulated with a blowing agent (typically 3.5% to 7% of bead 
weight). When subjected to prescribed heating in an expansion system, 
the beads puff up, expanding many times their original v olume into low 
density foam globules (called “prepuff” or “puff”) from which a variety of 
EPS foam products are molded.  
V.A.3.c.   “Expanded polystyrene (EPS) foam” means a lightweight, foam material, 
made of polystyrene, from which a variety of common item s are made, 
such as ice -chests, insulation board, protective packaging, and single-
use cups.  
V.A.3.d.   “Foam” means a solid material in a lightweight cellular form (having 
internal voids or cavities called cells that contain air or a gas) resulting 
from th e introduction or generation of gas bubbles throughout its mass 
during processing.  
V.A.3.e.   “Foam manufacturing operation” means any EPS production line, or portion of a production line, which processes raw EPS bead into final molded EPS product. Producti on line processes include, but are not 
limited to: pre -expansion, aging (pre -puff), and molding. The 
manufacturing process ends after the product exits the EPS mold. “Foam manufacturing operation” also means any production line processing 
methylene dipheny l diisocyanate (MDI), resins, and various hardeners 
and thickeners into foam products and which results in VOC emissions 
into the atmosphere. The manufacturing process ends after the product 
exits the drying tunnel.  
V.A.3.f.   “Non -VOC blowing agent” means a blowing agent which does not 
contain VOCs.  
V.A.3.g.   “Polystyrene” means any grade, class, or type of thermoplastic polymer, 
alloy, or blend that is composed of at least 80% polymerized styrene by 
weight.  
V.A.3.h.   “Raw material ” means all polystyrene, p olyethylene and polypropylene, 
and blowing agent used in the manufacture of foam products.  
V.A.4. Emission Limitations  
V.A.4.a.   By May 1, 2022,  for sources subject pursuant to Section V.A.1.a. and by 
May 1, 2024, for sources subject pursuant to Section V.A.1.b.,  owners 
and operators of foam manufacturing operations must either   28 V.A.4.a.(i)  Limit VOC emissions from foam manufacturing to 3.0 lbs. per 
100 lbs. of total material process, averaged monthly, or  
V.A.4.a.(ii)  Control VOC emissions from foam manufact uring by 90%. The 
control device must have a control efficiency of at least 95%.  
V.A.5.  Work Practices  
The owner or operator of any foam manufacturing operation must implement the following work 
practice requirements at all times to reduce VOC emissions fr om fugitive sources.  
V.A.5.a.   Store raw materials in closed, leak -free, labeled containers when not in 
use. 
V.A.5.b.   Cover open containers in a manner that minimizes evaporation into the 
atmosphere.  
V.A.6.  Monitoring  
V.A.6.a.   The owner or operator of foam manufacturing operations must operate 
and maintain the control device consistent with the manufacturer’s specifications.  
V.A.6.b.   By November 1, 2022, and every three (3) years afterward, owners or 
operator of foam manufacturing operations must conduct  a performance 
test during representative operations using EPA Method 24 (October 7, 
2020) to determine VOC content and EPA Method 18, 25, or 25A 
(November 14, 2018) to determine control efficiency of the emission 
control equipment.  
V.A.7.  Recordkeeping  
The following records must be kept for a period of five (5) years and made available to the 
Division upon request  
V.A.7.a.   Any records necessary to demonstrate that an exemption in Section 
V.A.2. applies.  
V.A.7.b.   The amount of raw material processed on a daily basis.  
V.A.7.c.   The type of blowing agent used.  
V.A.7.d.   The amount of blowing agent used on a monthly basis.  
V.A.7.e.   The total monthly VOC emissions.  
V.A.7.f.   For operators complying with the emission limitation in Section 
V.A.4.a.(i), the tota l monthly VOC emissions calculated on a pounds  per 
100 lbs. of material processed basis.  
V.A.7.g.   For operators that use a control device to comply with the emission limitations in Section V.A.4.a.  
V.A.7.g.(i)  A manufacturer guarantee of the control equipment’s emission control efficiency to demonstrate compliance with Section V.A.4.   29 V.A.7.g.(ii)  The amount of supplementary natural gas combusted in the 
control device on a monthly basis.  
V.A.7.g.(iii)  Records of performance tests conducted pursuant to Secti on 
V.A.6.  
V.A.7.h.  Records of calendar year VOC emission estimates demonstrating 
whether the foam manufacturing operation meets or exceeds the applicability threshold in Section V.A.1.  
V.A.8.  Reporting  
V.A.8.a.   Performance test protocols required for per formance tests under Section 
V.A.6.b. must be submitted to the Division for review at least thirty (30) 
days prior to testing and in accordance with AQCC Common Provisions 
Regulation Section II.C.  
V.A.8.b.   Beginning in 2024, the owner or operator must sub mit periodic reports 
(e.g., deviation reports, compliance certifications ) as required by the 
source’s operating permit.  
>>>>>> 
PART C Statements of Basis, Specific Statutory Authority and Purpose  
II. DATE, 2023  (Revisions to Part A, Section I. C.; and Part B, Sections  I.D.5., I.D.6., II., III.D., 
and V. ) 
This Statement of Basis, Specific Statutory Authority, and Purpose complies with the requirements of the 
State Administrative Procedure Act, § 24- 4-101, C.R.S., et seq., the Colorado Air Pollution Prevention 
and Control Act, § 25- 7-101, C.R.S., et seq., and the Air Quality Control Commission’s (Commission) 
Procedural Rules, 5 C.C.R. §1001- 1. 
Basis  
On October 7, 2022, EPA reclassified the Denver Metro/North Front Range (DM/NFR) to severe for the 
2008 8 -hour Oz one National Ambient Air Quality Standard of 75 parts per billion (ppb) (2008 ozone 
NAAQS), after 2019 -2021 ozone data failed to show attainment. See 86 Fed. Reg. 60926. Separately, 
EPA has also designated the DM/NFR as marginal nonattainment for the 2015 ozone NAAQS of 70 ppb, 
effective August 3, 2018 (83 Fed. Reg. 25776 (June 4, 2018)). On November 30, 2021, EPA expanded 
the boundary of the 2015 ozone nonattainment area to include all of Weld County, effective December 
30, 2021 (86 Fed. Reg. 67864). On Oc tober 7, 2022, EPA reclassified the DM/NFR and northern Weld 
County to moderate, after 2019 -2021 ozone data failed to show attainment. See 86 Fed. Reg. 60897.  
To ensure progress towards attainment of the 2008 and 2015 ozone NAAQS and respond to Colorado’s  
requirements under the Clean Air Act, the Commission adopted revisions to include reasonably available 
control technology (RACT) for major sources of volatile organic compounds (VOC) and nitrogen oxides 
(NOx) in the nonattainment areas, specifically expanding requirements for foam manufacturing, 
modifications to  requirements for  landfill and biogas fuel fired engines, modifications to requirements for 
process heaters , and a requirement for additional major source RACT analyses.  The Commission also 
adopted additional, state- only, state -wide requirements for stationary combustion engines.   30 Specific Statutory Authority  
The State Air Act, specifically § 25 -7-105(1), directs the Commission to promulgate such rules and  
regulations as are consistent with the legis lative declaration set forth in § 25- 7-102 and that are 
necessary for the proper implementation and administration of Article 7. The Act broadly defines air 
pollutant to include essentially any gas emitted into the atmosphere (and, as such, includes VOC, N Ox, 
methane and other hydrocarbons) and provides the Commission broad authority to regulate air pollutants. 
§ 25-7-105(1)(a)(I) directs the Commission to adopt a state implementation plan (SIP) to attain the 
NAAQS. § 25-7-106 provides the Commission maximum flexibility in developing an effective air quality 
program and promulgating such combination of regulations as may be necessary or desirable to carry out 
that program. § 25-7-106 also authorizes the Commission to promulgate emission control regulations 
applicable to the entire state, specified areas or zones, or a specified class of pollution. § 25-7-106(6) 
further authorizes the Commission to require owners and operators of any air pollution source to monitor, 
record, and report information. §§ 25-7-109(1)(a) and (2) of the Act authorize the Commission to 
promulgate regulations requiring effective and practical air pollution controls for significant sources and 
categories of sources and emission control regulations pertaining to nitrogen oxides and hydroc arbons.  
Purpose  
The following section sets forth the Commission’s purpose in adopting the revisions to Regulation 
Number 26, and includes the technological and scientific rationale for the adoption of the revisions.  
Stationary Combustion Engines  
 
In 2020, the Commission adopted state -wide, state -only requirements to minimize emissions from natural 
gas-fired reciprocating internal  combustion engines  greater than or equal to 1,000 horsepower  (hp). At 
that time, the Commission requested that the Division consider evaluating strategies to increase the 
electrification of engines, lower emissions standards for engines, and possible controls applicable to 
smaller engines. In response to this directive and to further address NOx emissions affecting Colorado’s 
ability to meet the ozone NAAQS , as well as other state goals , the Commission adopted additional NOx 
emission limits for natural gas -fired engines greater than or equal to  100 hp and diesel engines greater 
than or equal to 500 hp. The Commission also adopted new reporting requirements  for natural gas -fired 
engines below 100 hp. Based on Division data, there are a large number of engines  in this category  of 
engines below 100 hp operating in the oil and gas sector throughout  the state. However, data on these 
engines and the associated NOx emissions are not readily available  because many of these sources are 
exempt from permitting and APEN requirements in Regulation Number 3.  
 
For engines placed in service, modified, or relocated after January 30, 2024 , the Commiss ion adopted, 
generally, more stringent NOx standards . However, for lean burn engines, the NOx standard is the same 
whether the engine is currently in use at a site or brought on at a later date.  The Commission also intends 
that any engines subject to a mor e stringent standard under a permit must still comply with that more 
stringent  limit. The Commission adopted varying timing requirements for owners or operators to meet the 
emission  standards, based on the location of subject engines inside and outside of the 8- hour ozone 
control area. Owners or operators with any engines in the 8-hour ozone control area are subject to a 
more  aggressive timeline, which requires 100% of engines inside the 8-hour ozone control area to meet 
the emission standards by May 1, 2027 , and 100% of engines outside the 8-hour ozone control area meet  
the emission standards by May 1, 2029. Operators with no engines inside the 8-hour ozone control area 
must follow the second timeline and meet the standards of at least 20% of engines each y ear from 2024 
to 2029.   
 
The Commission intends that the emission standards in Table 5 are a gram per horsepower -hour (g/hp-
hr) limit based on appropriate averaging times. The Commission also intends that operators demonstrate 
compliance with the certification and recordkeeping requirements through the performance testing results 
required by Section I.D.6.c . and the portable analyzer results obtained in accordance with Section 
I.D.6.d., using the appropriate averaging times.   31  
Major Source RACT  
Due to the re classifications to severe and moderate, Colorado must submit revisions to its SIP to address 
the Clean Air Act’s (CAA) ozone nonattainment area requirements, as set forth in CAA §§ 172, 182(b), 
182(d), and the final SIP Requirements Rules. Severe SIPs must  include provisions that require the 
implementation of RACT for major sources of VOC and/or NOx (i.e., sources that emit or have the 
potential to emit 25 tpy or more) and for each category of VOC sources covered by a Control Technique 
Guideline (CTG) for w hich Colorado has sources in the nonattainment area.  
Therefore, to address the severe nonattainment area requirements under CAA § 182(d), the Commission 
adopted revisions to Regulation Number 26 to include RACT requirements in Colorado’s ozone SIP for 25 
tpy major sources of VOC and/or NOx including expanding the foam manufacturing operations. In 
response to EPA concerns and limited disapproval, the Commission also adopted revised requirements 
for process heaters, landfill and biogas engines,  a coil coatin g facility,  and periodic reporting.   
Foam Manufacturing  
In response to the DM/NFR being reclassified to severe nonattainment under the 2008 ozone NAAQS the 
Commission adopted revisions to Regulation 26 to expand VOC control requirements  initially adopted in 
December 2020  to foam manufacturing operations with VOC emissions greater than or equal to 25 tons 
per year (tpy). These provisions include work practice, monitoring, and recordkeeping requirements for 
foam manufacturing operations.  
In addition, to address EPA’s concern with the lack of specified reporting, and as discussed further below , 
the Commission adopted SIP revisions to include requirements for sources to comply with the periodic 
reporting requirements in the operating permit. This periodic repo rting can be annually, biannually, or 
more frequently and includes reports of monitoring and/or permit deviations, including probable cause 
and corrective actions taken, and compliance certifications, stating the compliance status of each 
requirement of the permit over the certification period.  
Landfill and Biogas Fuel Fired Engines  
In 2020, the Commission expanded the NOx emission limit requirements for compression ignition 
reciprocating internal combustion engines (RICE) and combustion process adjustment requirements for 
stationary RICE to landfill and biogas fired engines at major sources (50 tpy). Considering the potentially 
subject sources at that time, the Commission adopted the 2.0 g/hp -hr NOx emission limit in EPA’s NSPS 
JJJJ for landfill/digester ga s fired engines. In reviewing the adopted requirements and considering the 
remaining subject engines, EPA has raised concerns with the NOx emission limit and testing 
requirements. The Commission  re-reviewed the subject engines, several having since  been removed 
from service, and is adopting a revised  NOx emission limit of 1.5 g/hp- hr for these  engines. The 
Commission also  expand ed the periodic performance testing requirements currently applicable to other 
subject major source engines.   
Process Heaters  
In 2021, the Commission adopted additional requirements for refinery fuel fired process heaters at major 
NOx sources. In response to EPA’s comments and concerns and to allow for further evaluation, the 
Commission  removed  the NOx emission limits for these heaters . The process heaters will continue to be 
subject to combustion process adjustment requirements, as they have been since the 2021 revisions, and 
performance testing requirements.  The Commission directs the Division to return to the Commission with 
propos ed revisions in the future related to these heaters following further useful input from EPA, if 
necessary and appropriate.   32 Golden Aluminum (coil coating facility)  
In 2020, the Commission evaluated the NOx emission points at Golden Aluminum as it beca me a major 
source of NOx emissions under the 50 tpy serious major stationary source threshold. Golden Aluminum is 
a coil coating operation and, therefore, subject to the coil coating provisions in Regulation Number 25 
(formerly in Regulation Number 7, Part C), w hich were adopted many years ago based on the 
recommendations in EPA’s corresponding coil coating CTG. EPA is taking issue with Colorado’s reliance 
on EPA’s long -standing interpretation and position that states may utilize EPA’s control techniques 
guidelin es (CTG) recommendations and definition of the subject VOC source category when revising the 
state’s SIP to include provisions that require the implementation of RACT for that particular VOC source 
category (i.e., SIP RACT). Specifically, EPA has proposed a limited disapproval because Colorado did 
not evaluate VOC emission points at this coil coating operation that were also not addressed in EPA’s coil 
coating CTG. Therefore, the Commission adopted a requirement for Golden Aluminum to conduct and 
submit a RACT analysis to the Division for further evaluation of the VOC -emitting points at issue in EPA’s 
proposed disapproval . 
Periodic Reporting  
To address  EPA’s concern with the lack of specified reporting (see EPA’s limited disapproval, discussing 
EPA’s perceiv ed lack of periodic reporting sufficient to determine compliance by regulated entities (88 
Fed. Reg. 29827, May 9, 2023)), to avoid federal sanctions the Commission included requirements for 
major sources to comply with the periodic reporting requirements in the operating permit , specifically foam 
manufacturing and combustion equipment at major NOx sources . This periodic reporting can be annually, 
biannually, or more frequently and includes reports of monitoring and/or permit deviations, including 
probable cause and corrective actions taken, and compliance certifications, stating the compliance status 
of each requirement of the permit over the certification period.  
The Commission also made typographical, grammatical, and formatting corrections throughout the 
regulations.  
Incorporation by Reference  
The Commission will update regulatory references as needed as opportunities arrive.  
Additional Considerations  
Colorado must revise Colorado’s ozone SIP to address the severe ozone nonattainment area 
requirements.  The CAA does not expressly address all of the provisions adopted by the Commission. 
Rather, federal law establishes the ozone NAAQS and requires Colorado to develop a SIP adequate to 
attain the NAAQS. Therefore, the Commission adopted certain revisions to Regulation Number 26 to 
satisfy Colorado’s nonattainment area obligations and further achieve reductions of ozone precursor 
emissions. These revisions do not exceed or differ from the federal act due to state flexibility in 
determining what control strategies to implement to reduce emissions. However, where the proposal may 
differ from federal rules under the federal act, in accordance with § 25- 7-110.5(5)(b), CRS, the 
Commission determines:  
(I) The revisions to Regulation Number 26 address foam manufacturing,  landfill biogas fuel fired 
engines, a coil coating operation, and process heaters. NSPS T, MACT DDDDD, MACT ZZZZ, 
and MACT SSSS may also apply to and the above listed equipment and operations. However, 
the revisions to Regulation Number 7 apply on a broader basis.  
(II) The federal rules discussed in (I) are primarily technology -based in that they largely prescribe the 
use of specific technologies or work practices to comply.   33 (III) The CAA establishes the 2008 and 2015 ozone NAAQS and requires Colorado to develop SIP 
revisions that will ensure attainment of the NAAQS. The ozone NAAQS was not determined 
taking into account concerns unique to Colorado. Similarly, EPA develops NSPS or NESHAP 
considering national information and data, not Colorado specific issues or concer ns. In addition, 
Colorado cannot rely exclusively on a federally enforceable permit or federally enforceable NSPS 
or NESHAP to satisfy Colorado’s ozone nonattainment area RACT obligations. Instead, Colorado 
can adopt applicable provisions into its SIP directly, as the Commission has done here.  
(IV) In addition to the 2008 NAAQS, Colorado must also comply with the lower 2015 ozone NAAQS. 
These current revisions may improve the ability of the regulated community to comply with new 
requirements needed to attain the lower NAAQS insofar as RACT analyses and efforts conducted 
to support the revisions adopted by the Commission may prevent or reduce the need to conduct 
additional RACT analyses for the more stringent NAAQS.  
(V) EPA has established Colorado’s SIP  RACT implemen tation deadlines. There is no timing issue 
that might justify changing the time frame for implementation of federal requirements.     
(VI) The revisions to Regulation Number 26 strengthen Colorado’s SIP. These sections currently 
address emissions from foam manufacturing,  landfill and biogas fuel fired engines , a coil coating 
operation,  and process heaters , while  allowing for continued growth of Colorado’s industry.  
(VII) The revisions to Regulation Number 26 establish reasonable equity for owners and operators 
subject  to these rules by providing the same standards for similarly situated and sized sources.  
(VIII)  If EPA does not approve Colorado’s SIP, EPA may promulgate a Federal Implementation Plan; 
thus potentially determining RACT for Colorado’s sources. This outcome may subject others to 
increased costs.  
(IX) Where necessary, the revisions to Regulation Number 26 include minimal monitoring, 
recordkeeping, and reporting requirements that correlate, where possible, to similar federal or 
state requirements.  
(X) Demonstrated technology is available to comply with the revisions to Regulation Number 26.  
Some of the revisions expand upon requirements already applicable. The revisions concerning 
major sources of NOx generally reflect current emission controls and work practices.  
(XI) As set f orth in the Economic Impact Analysis, the revisions to Regulation Number 26 will reduce 
emissions in a cost -effective manner.  
(XII) Alternative rules could also provide reductions in ozone, VOC, and NOx to help to attain the 
NAAQS. However, a no action alternati ve would very likely result in an unapprovable SIP.  
Findings of Fact  
To the extent that § 25- 7-110.8, C.R.S., requirements apply to this rulemaking, and after considering all 
the information in the record, the Commission hereby makes the determination that  
(I) These rules are based upon reasonably available, validated, reviewed, and sound scientific 
methodologies, and the Commission has considered all information submitted by interested 
parties.  
(II) Evidence in the record supports the finding that the rules shall r esult in a demonstrable reduction 
of greenhouse gas and VOC emissions.   34 (III) Evidence in the record supports the finding that the rules shall bring about reductions in risks to 
human health and the environment that justify the costs to implement and comply with the rules.  
(IV) The rules are the most cost -effective alternative to achieve the necessary reduction in air 
pollution and provide the regulated entity flexibility.  
(V) The selected regulatory alternative will maximize the air quality benefits of regulation in the m ost 
cost-effective manner.  
_________________________________________________________________  