Colorado’s environmental regulatory landscape continues to evolve as the state tightens pollution controls, expands emissions reporting programs, and responds to federal uncertainty around air quality and climate policies. Navigating this dynamic environment requires understanding where Colorado is expanding its requirements, where federal requirements may be shifting, and how these overlapping developments shape compliance obligations in the year ahead.
Colorado Regulatory Hot Topics
Growing Stringency in Ozone and SIP-Related Rulemakings
Colorado’s 2026 rulemakings are heavily influenced by the state’s ongoing efforts to manage ozone nonattainment. One of the more significant actions in this regard is the state’s request to reclassify northern Weld County from “serious” to “severe” nonattainment under the 2015 ozone standard. This voluntary step allows the Colorado Department of Public Health and Environment (CDPHE) to broaden its regulatory tools, including expanded RACT obligations and more stringent permitting requirements for oil and gas transmission, storage, and combustion sources located in this area. Updates to Regulation 3 and Regulation 7 reflect this shift, particularly in the areas of public notice for permit modifications, emissions credit procedures, and alignment with Colorado’s EJ-screening methodology.
Expansion of Colorado’s Air Toxics Programs (HB22‑1244 and Regulation 30)
Colorado continues to implement its ambitious air toxics agenda initiated under HB22‑1244. Annual air toxics reporting began in 2024, accompanied by the launch of a long‑term network of monitoring sites across the state. In January 2025, Colorado designated its first five priority toxic air contaminants: formaldehyde, benzene, hexavalent chromium, ethylene oxide, and hydrogen sulfide. By April 2026, the state will establish health‑based standards and emission control requirements for these contaminants, which may drive the need for permitting at facilities emitting these pollutants. Looking ahead, Colorado will revisit and potentially expand the list of regulated toxics every five years as monitoring and health assessments evolve. Reporting requirements under the air toxics program is further discussed in the reporting section below.
New Engine Requirements Under Regulation 26
Colorado’s engine rulemaking was a major regulatory driver affecting oil and gas, industrial, and manufacturing facilities. Regulation 26 imposed phased NOX standards on natural gas and diesel engines, depending on horsepower, combustion type, and installation date when adopted in April 2023. Compliance deadlines range from 2025 through 2029, with more aggressive timelines for engines located within ozone control areas. Operators must conduct performance testing, maintain extensive records, and complete annual NOX analyzer monitoring beginning this year. These requirements significantly affect maintenance planning and emissions budgeting for engine fleets. Any facility that requires a modification to meet their engine limits must submit a permit application one year prior to their compliance date. With May 1, 2027, being the deadline to bring at least 50% of subject diesel engines into compliance with the new emission standards, May 1, 2026, will be the deadline for submitting the first wave of diesel engine permit applications!
Lower PM2.5 Standard and Implications for Permitting
EPA’s revised annual PM2.5 standard of 9.0 µg/m³, effective in May 2024, poses new challenges for Colorado projects seeking air permits. Although Colorado’s existing monitors remain below the new standard, the lower threshold reduces the amount of emissions a project may add before triggering cumulative modeling issues. CDPHE is currently updating its background concentration values to remove wildfire‑related exceptional events, which may further influence permitting outcomes. Even amid federal discussion of revisiting the PM2.5 rule, facilities must prepare for tighter modeling expectations.
Regional Haze Disputes and Federal Pushback
Colorado’s 2022 Regional Haze SIP was recently partially disapproved by EPA. While EPA has generally proposed approval of most aspects of the proposed SIP, they are specifically proposing disapproval of the portion of the SIP regarding enforceable source closures of coal-fired power plants. Although Colorado may still implement source closures under state law, EPA’s disapproval introduces uncertainty around whether Colorado will need to revise its SIP or operate temporarily under a federal implementation plan. This tension highlights broader policy conflicts between Colorado’s climate strategies and shifting federal energy priorities.
Colorado Reporting Updates and Reminders
Stormwater Reporting and Stormwater Management Plan (SWMP) Maintenance (February–March)
Annual stormwater reports are due between mid‑February and the end of March, depending on the specific industrial permit. Beyond annual reporting, facilities must adhere to recurring inspection and documentation requirements of quarterly visual assessments and monitoring results, routine site inspections, and comprehensive annual evaluations. Importantly, SWMPs must be revised whenever there are operational changes, releases, or CDPHE inspection findings requiring updates.
Facilities covered by General Permit COR900000 for Stormwater Discharges Associated with Non-Extractive Industrial Activity may be subject to a new requirement for the annual report due March 31 – facilities who, due to lack of a measurable storm event, have not reported any discharge monitoring results for the first full four quarters for which their permit certification is effective are required to include a Discharge Preparation Plan with their annual report submittal. The Discharge Preparation Plan should detail facility-specific conditions likely to produce a measurable storm event, including assessment of rainfall and snowmelt conditions, procedures to track precipitation, and methods for collecting samples.
Hazardous Waste Biennial Report (March 1)
All Large Quantity Generators (LQGs) must submit biennial hazardous waste reports in even numbered years covering activities for the prior calendar year. Reports must include generator identification details, off‑site shipment information, transporter data, waste descriptions, hazard classifications, reduction efforts, and certified signatures. All Small Quantity Generators (SQGs) and LQGs should already be registered in the e‑Manifest system.
Tier II Chemical Inventory Reporting (March 1)
Colorado requires Tier II emergency planning reports to be submitted through AccessGov which also requires a fee. Colorado maintains Tier II reporting information webpage with useful information. All Tier II reports must be created in EPA’s newest version of the Tier2 Submit software, available for download from CDPHE’s website. Some jurisdictions may also require facilities to submit Tier II data directly to the Local Emergency Planning Committee (LEPC). Facilities should be aware of updated hazard categories under OSHA’s 2024 Hazard Communication Standard that take effect for the RY2026 reports due in 2027, significantly expanding the number of hazard classifications. Early review of updated SDSs is highly recommended.
Refrigerant Management and Chronic Leaker Report (March 1)
The EPA’s Refrigerant Management Rule continues to require reporting for regulated appliances containing at least 50 pounds of Class I or II ODS if leaks exceed 125% of full charge in a year. Beginning in 2027, similar chronic leak reporting will apply to HFCs and substitutes with global warming potential above 53, for leaks occurring in 2026.
GHG Reporting Under Regulations 22 and 7
Despite potential changes at the federal level, Colorado’s GHG reporting obligations remain firmly in place. Facilities subject to EPA Mandatory Reporting must submit their reports to CDPHE by March 31. Oil and gas facilities then submit a more expansive annual GHG report by June 30 under Regulation 7, which also captures criteria pollutant emissions. CDPHE has signaled its intent to maintain state-level GHG reporting even if federal reporting comes into question, and the Division is developing alternative submission processes if federal systems become unavailable. For reports typically due by March 31, CDPHE may grant flexibility for an extension in 2026 due to the federal uncertainty.
Annual APEN Submission Requirements (April 30)
APENs must be updated when significant emission changes occur, even in years without major facility modifications. Colorado recently updated several APEN forms, making it important to pull the most current versions from CDPHE’s website. For sources within ozone nonattainment areas, thresholds for NOX and VOC are particularly low, and even small year-to-year shifts can trigger filing requirements. Changes are on the horizon for annual APEN reporting, but for 2026, it’s business as usual.
Oil & Gas Reporting: A Concentrated Q2 Workload
Oil and gas operators face an intense cluster of reporting deadlines from April through July. Reporting obligations include tank and dehydrator reports, LDAR data, pneumatic controller records, engine testing and monitoring summaries, transmission segment certifications, and the comprehensive Regulation 7 emissions inventory. The Regulation 7 emission inventory required monthly emissions reporting for the previous calendar year beginning in 2025 and this requirement will also be present for reports due in 2026.
Air Toxics Reporting (June 30)
For 2026, Colorado’s air toxics reporting remains unchanged, but major rule updates will affect the following reporting year. These include a reduction in the number of reportable toxic air contaminants, new de minimis thresholds, new exemptions for certain small sources, and the addition of pollutants such as black carbon and ultrafine particles. For a more information about air toxics program in Colorado, see this related article, “What Your Facility Needs to Know for 2025 and 2026 TAC Reporting”.
Building Benchmarking Under Regulation 28 (November 1)
Certain buildings 50,000 sq ft and larger must report energy performance data using ENERGY STAR Portfolio Manager. New legislation moves the reporting deadline to November 1 and reclassifies 2026 energy limits as non-enforceable goals. However, the long-term trajectory of the program points toward increasingly stringent performance standards.
Facility-Wide GHG APEN Requirements (December 31)
Any operator submitting GHG data under Regulation 22 or Regulation 7 must also submit a facility-wide GHG APEN by December 31. This requirement ensures alignment between program reports and supports calculation of Colorado’s GHG emissions fees.
Federal Updates Snapshot
EPA Enforcement Declines and Focus Shifts
EPA enforcement activity has dropped significantly in the past year, with only a single compliance advisory released in 2025 and historically low levels of litigation. Current priorities focus on imminent public health risks, illegal HFC imports, and select waste‑related concerns. Enforcement tied to methane emissions, environmental justice, or expanded oversight has been deemphasized by the current EPA administration.
Federal Deregulatory Efforts Intensify
EPA has initiated more than 30 deregulatory actions impacting oil and gas standards, electric power rules, wastewater effluent guidelines, and GHG reporting programs. Several methane rule compliance dates, originally set under NSPS OOOOb and OOOOc, have already been delayed until 2027 or later.
GHG Reporting and the Endangerment Finding Under Review
The federal GHG Reporting Program may be significantly scaled back. A 2025 proposal would eliminate reporting for nearly all source categories after reporting year 2024 and suspend Subpart W reporting until 2034. Additionally, EPA announced on February 12, 2026 a final rule that rescinds the 2009 GHG Endangerment Finding, a move that fundamentally affects greenhouse gas regulation nationwide. Litigation is virtually guaranteed on this action.
PFAS Oversight Continues to Expand
While many federal programs face rollback, PFAS or “forever chemicals” regulation remains an area of ongoing development. TRI reporting thresholds now cover more than 200 PFAS, CERCLA continues to classify PFOA and PFOS as hazardous substances, and stormwater and wastewater programs are incorporating new PFAS monitoring requirements. Drinking water rules have narrowed their scope but extended compliance timelines, reducing immediate burdens while maintaining long‑term expectations.
HFC Management Rule Now in Effect
Under 40 CFR Part 84, hydrofluorocarbons (HFCs) and refrigerant substitutes with global warming potential above 53 are now regulated with a January 1, 2026, effective date for most requirements. The rule is similar to the requirements for ODS appliances under 40 CFR Part 82, Subpart F, with some differences, including a lower capacity threshold of 15 pounds for leak repair requirements. For more information on refrigerant management, see our Refrigerant Management Services (ODS and HFC) webpage.
Key Takeaways
Colorado continues to expand its environmental regulatory framework, particularly in the areas of ozone control, toxic air contaminants, emissions monitoring, and engine compliance. At the same time, federal rules remain in transition, creating uncertainty that increases the importance of strong internal planning and consistent data management. Successful compliance in 2026 depends on early preparation, careful tracking of regulatory changes, and integration of data across reporting programs to ensure consistent, accurate submissions throughout the year.
Resources:
- To stay current on our Colorado reporting requirements, download a copy of the 2026 Colorado annual reporting compliance calendar.
- For a copy of our slide deck from our recent presentation on 2026 Annual Compliance Reporting and Hot Topics in Colorado reach out to Zoe Stone.
- For support with your upcoming reporting requirements or questions on regulatory changes in Colorado, reach out to Chris Platt with our Denver office, or call 720.638.7647.
