The New Mexico Environment Department (NMED) has announced noteworthy changes to its very small emission rate modeling waiver requirements. Effective July 27, 2023, these revisions are the first significant updates to the modeling waiver process in over five years.
NMED’s move involves three major modifications of very small emission rate modeling waiver requirements. These alterations will result in a more detailed and clear modeling waiver process. Among the notable adjustments, NMED has significantly lowered the thresholds for very small emission rates on the Air Dispersion Modeling Waiver form. Previously, the department mandated facilities to consider facility-wide emissions for such modeling waivers. However, the latest updates introduce an important shift. Now, project-specific emissions are factored into the equation. This progressive approach is set to facilitate smoother permitting procedures for facilities while maintaining existing air quality standards.
Furthermore, the amended waiver form now stipulates an essential geographical prerequisite. To be eligible for a very small emission rate-based modeling waiver, facilities must be located at least 2 kilometers away from the nearest Class I area.
In the realm of construction permit applications, demonstrating compliance with applicable air quality standards is often one of the most challenging requirements. This often entails intricate air dispersion modeling, which includes facility and source-specific inputs, representative meteorological data, and the addition of surrounding sources. Acknowledging the nuances of the field, NMED recognizes that prior modeling endeavors can serve as viable benchmarks in certain instances. To facilitate a smoother permitting process, the department has extended the option for modeling waivers, granting applicants the flexibility to navigate the regulatory landscape more efficiently.
If emissions have been modeled using the latest modeling procedures and air quality standards, and this modeling is still valid for the current standards, then the modeling waiver form may be submitted to request approval of a modeling waiver. NMED will determine on a case-by-case basis if the modeling waiver can be granted, and the waiver discussion and written waiver approval should be included in the modeling section of the application.
NMED has performed generic modeling to demonstrate that the following small sources do not need modeling. The application must include a modeling waiver form to document the basis of the waiver. The table below presents the comparison of the modeling waiver thresholds before and after 7/27/2023. Modeling is waived if emissions of a pollutant for the project are below the amount updated after 7/27/2023.
Updated Very Small Emission Rate Modeling Waiver Thresholds (updated 7/27/2023)
| Pollutant | If all emissions come from stacks 20 feet or greater in height and there are no horizontal stacks or raincaps (lb/hr) | If all emissions come from stacks 20 feet or greater in height and there are no horizontal stacks or raincaps (lb/hr) |
| Before 7/27/2023 | After 7/27/2023 | Before 7/27/2023 | After 7/27/2023 |
| CO | 50 | 16.037 | 2 | 2.580 |
| H2S (Pecos-Permian Basin) | 0.1 | 0.114 | 0.02 | 0.015 |
| H2S (Not in Pecos-Permian Basin) | 0.01 | 0.022 | 0.002 | 0.003 |
| Lead | Waiver not available. | 0.005 | Waiver not available. | 0.001 |
| NO2 | 2 | 0.189 | 0.025 | 0.024 |
| PM2.5 – Point Sources | 0.3 | 0.056 | 0.015 | 0.009 |
| PM 2.5– Volume Sources | – | – | – | 0.003 |
| PM10– Point Sources | 1.0 | 0.255 | 0.05 | 0.039 |
| PM 10–Volume Sources | – | – | – | 0.015 |
| SO2 | 2 | 0.179 | 0.025 | 0.023 |
| Reduced sulfur (Pecos-Permian Basin) | 0.033 | 0.033 | Waiver not available. | Waiver not available. |
| Reduced sulfur (Not in Pecos-Permian Basin) | Waiver not available. | Waiver not available. | Waiver not available. | Waiver not available. |
For an in-depth understanding of these important changes, visit NMED’s Air Quality Modeling page, where you can access essential resources such as the 2022 Modeling Guidelines and the 2023 Modeling Waiver Form. For inquiries related to Air Dispersion Modeling or Modeling Waivers, engage with the Trinity Albuquerque Office at 505.266.6611.
Trinity is also set to host multiple Air Dispersion Modeling Workshops, which offer a comprehensive dive into the world of air dispersion modeling. Participants can expect a holistic grasp of air dispersion modeling principles through interactive multimedia exercises, hands-on engagement with computer-based modeling software, and collaborative discussions. These workshops will delve into transport and dispersion, atmospheric turbulence, stack characterization, building downwash, and terrain impacts. Attendees can expect to develop critical skills related to U.S. EPA models, including AERMOD, AERSCREEN, and a brief introduction to CALPUFF, CAMx, and CMAQ.
