On May 28, 2026, the Colorado Department of Public Health and Environment (CDPHE) Air Pollution Control Division (APCD) issued the long-anticipated General Permit 12 (GP12), a facility-wide general permit for minor New Source Review (NSR) well production facilities. Alongside the permit itself, the Division released Permitting Section Memo 26-01 and instructions for a new GP12 dispersion modeling workbook. Together, these documents reshape how upstream operators will permit new well production facilities in Colorado.
GP12 Replaces GP09/GP10 for New Registrations
GP12 is available only for equipment located at well production facilities as defined in Regulation Number 7. Once GP12 opens for registration, GP09 and GP10 will no longer be available for new registrations, though existing GP09/GP10 registrations remain active and sources operating under those permits maintain coverage. The Division’s announcement of the final GP12 indicated they anticipate opening the permit for application submission in summer 2026.
Eligible source types under GP12 include:
- Storage tanks (condensate, crude oil, intermediate hydrocarbon liquids, and produced water)
- Hydrocarbon liquids truck loadout
- Natural gas venting and flaring from separators
- Routine or predictable emissions (ROPE)
- Natural gas-fired and diesel-fired reciprocating internal combustion engines
- Fugitive component leak emissions
Importantly, GP12 serves as an all-or-nothing permit option at the facility level. If an operator elects to use GP12, all permit-required emission units at the facility must be covered under it. Operators cannot, for example, place tanks under GP12 and an engine under a traditional construction permit or GP02. Facilities with equipment that does not qualify for GP12 must instead rely on traditional construction permits, alone or in combination with other general permits. This differs from previous equipment-specific general permits (such as GP02 for engines) that could be used in combination with other traditional construction permits and/or general permits.
GP12 may not be used for new major stationary sources or for modifications at existing major stationary sources subject to PSD or Nonattainment NSR. Sources that become major solely because of a future nonattainment area reclassification can keep their GP12 coverage, but their ability to modify the registration is restricted unless the revision effectively renders the facility minor or synthetic minor.
A Lifetime Permit – With Construction Deadlines
Unlike GP09 and GP10, a GP12 registration covers both construction and operation and does not expire over the operational life of the facility, provided construction timelines are met. The registration will expire if the operator fails to commence construction, modification, or operation within 18 months of the registration date, discontinues construction for 18 months or more, or fails to complete construction within a reasonable time of the estimated completion date. Because “commencement of construction” for well production facilities means the date drilling begins (or other permanent site changes occur), operators that spud wells well in advance of completion should track the 18-month clock carefully. The Division may grant extensions of the deadline.
The advantage of general permits is that registration is conditionally certified from the date it is deemed complete. Per GP12 conditions, the Division will determine completeness of the general permit registration request within 60 days of the date of receipt and will provide written notification to the applicant. If the applicant does not receive notification in that timeframe, the registration request is automatically deemed complete.
Per-Unit APENs, Fees, and Notices of Startup
The registration mechanics differ from the single-APEN approach many operators used under GP09/GP10. Under GP12, operators must submit individual equipment-specific APENs and individual APEN filing fees ($410 per APEN starting July 15, 2026) for every emission unit, with each unit assigned its own AIRS point number. The GP12 has its own filing fee of $5,629. A facility with condensate tanks, produced water tanks, loadout, ROPE, and an engine would therefore submit five APENs and five sets of fees for the application to be deemed complete. The Division will, however, issue a single facility-wide approval letter.
Modifications follow the same logic: changing permitted limits or equipment requires a new complete registration, including APENs and general permit fees for every AIRS point being modified.
Emission Factors and Ongoing Sampling Obligations
GP12 continues Colorado’s emphasis on site-specific emissions data. Storage tanks, separators, and ROPE sources are subject to initial and periodic sampling requirements to develop updated emission factors, and actual emissions must be calculated using the most recently developed factors. For ROPE, operators must use the higher of the most recent sampling-derived factor or the factor referenced in the most recent approval letter. Representative emission factors may be used for initial registration of new facilities, but operators bear the compliance risk if those factors underestimate actual emissions, and existing units converting to GP12 generally must rely on state-default factors or site-specific data.
NAAQS Compliance and the New GP12 Modeling Workbook
New signature features of the GP12 program are the region-specific modeling workbooks, which streamline National Ambient Air Quality Standards (NAAQS) and Colorado Ambient Air Quality Standards (CAAQS) demonstrations for new facilities. The workbook is underpinned by a study involving thousands of AERMOD runs using emission rates and stack parameters typical of equipment found at Colorado well production facilities. Rather than running site-specific dispersion modeling, applicants enter their project data into the workbook, which calculates representative ambient impacts based on the conservative results of that underlying study.
Modeling Workbook Applicability
The workbook is reserved exclusively for newly constructed facilities seeking GP12 coverage. Modifications to an existing GP12 registration and conversions from other permit types to GP12 cannot use the workbook and must instead pursue a Form APCD-114 modeling determination and/or a site-specific ambient air impact analysis.
Even for new facilities, the workbook may be used only if all of the following are true:
- All emission units are point sources with unobstructed vertical releases. Stack screens and rain-protective designs that do not impede exhaust flow are acceptable, but conventional rain caps are considered obstructions, and capped or horizontal releases are excluded, as are area and volume sources such as haul roads and fugitives.
- All emission units fall into three source categories:
- heaters (HTR),
- enclosed combustion devices (ECD), and
- engines (ENG).
- Every emission unit is located at least 10 meters from the fenceline or ambient air boundary. Where no physical fence exists, an ambient air boundary may be established through measures such as no-trespassing signage, surveillance monitoring, daily site visits, or on-site personnel.
- No significant structures could contribute to building downwash from the facility’s emission sources.
Facilities that fall outside any of these conditions (for example, a tank battery whose ECD stacks sit closer than 10 meters to the property line) will need to plan for the APCD-114 process from the outset. Pursuing a Form APCD-114 modeling determination and/or a site-specific ambient air impact analysis does not disqualify use of the GP12, just use of the region-specific modeling workbooks.
How the Workbook Works
The Division has published separate workbooks for ten GP12 regions, each built on unique meteorology and background pollutant concentrations. Some regions sharing the same meteorology and background data are combined into a single workbook. Facilities near a region border should verify their region using the Google Earth kmz file CDPHE provides or contact the Dispersion Modeling Unit (DMU) for guidance.
Applicants must also characterize the site as flat or complex terrain. For GP12 purposes, flat terrain generally has surrounding slopes under 10%, while complex terrain has features with slopes greater than 10%. Flat terrain can be demonstrated using topographical map contours or a Google Earth elevation profile: if the elevation within a 1,000-foot radius does not rise more than 100 feet above the facility elevation, the terrain may be characterized as flat. Facilities in mountainous regions will typically be complex terrain, while facilities on the eastern plains (including those in the 2008 and 2015 ozone nonattainment areas) may be able to support a flat terrain demonstration, which generally yields lower calculated impacts.
The workbook accommodates up to 50 emission sources. For each source, the applicant selects the equipment type, enters hourly criteria pollutant emission rates (lb/hr), the shortest distance to the fenceline (meters), and stack parameters: height, exit temperature, exit velocity, and stack diameter (with a minimum exit velocity of 0.1 m/s required for ECDs). A helpful efficiency for tank batteries and multi-unit pads: multiple identical units may be modeled as a single source by entering one unit’s stack parameters, the summed emissions from all units, and the shortest fenceline distance among them.
The Results tab sums the calculated facility impacts with default regional background concentrations and compares the totals against the NAAQS/CAAQS for NO2 (1-hour, annual), CO (1-hour, 8-hour), SO2 (1-hour, 3-hour, annual), PM2.5 (24-hour, annual), and PM10 (24-hour), returning a simple Yes/No compliance indication for each.
Submittal Options
The completed workbook must be submitted to DMU with supporting documentation, including a scaled facility layout showing source locations and the facility boundary, documentation of stack parameters, terrain documentation if flat terrain is claimed, and any DMU correspondence. DMU will approve or reject the submission, and an approved workbook package becomes part of the permit record with the GP12 application.
If the workbook cannot demonstrate compliance, operators may pursue a Form APCD-114 modeling determination or a full site-specific AERMOD analysis. Detailed instructions, regional workbooks, and the supporting report are available on CDPHE’s Air Quality Modeling Guidance for Permits website.
Operators should note that, except where a facility qualifies as exempt from further modeling determinations under the Permitting Section Addendum, Dispersion Modeling Unit approval must be obtained before a GP12 application can be deemed complete.
What Operators Should Do Now
With GP09 and GP10 closing to new registrations, operators planning new well production facilities in Colorado should begin aligning their permitting strategies with GP12 requirements. Facilities considering conversion of existing permits to GP12 face additional constraints on emission factors and modeling demonstration.
To discuss how the new GP12 may affect your upcoming projects, contact Trinity’s Colorado office at 720.638.7647.
