Attainment Planning Using Ozone Modeling
Summary
To aid in evaluating the progress of existing emission control programs, assess the benefit of potential additional emissions control strategies, as well as to develop Attainment Demonstrations for RAQC region residents and U.S. EPA in accordance with State Implementation Plan (SIP) requirements, the RAQC engages in emissions analyses and photochemical modeling efforts. Photochemical modeling estimates the effects of emissions on ambient air quality using a grid-based computer model that simulates air pollution episodes impacting the entire RAQC region. The modeling tool is first used to replicate a recent historical year’s ozone monitoring data with modeling results using historic emissions data. It then estimates the air quality changes for a future milestone year by holding meteorology and out-of-area emissions constant while studying reductions of local emissions. It is the most effective tool available and is EPA-required for determining the cause of serious air pollution problems and what local emissions can be reduced to improve regional air quality. Photochemical modeling allows for the assessment of:
- How sensitive pollutants are to varying parameters such as meteorological conditions and emission rates
- How sensitive pollutants are to control scenarios
- Efficacy of proposed control strategies
Photochemical modeling is completed using EPA-approved modeling platforms and methodologies. For attainment planning modeling efforts, a detailed modeling protocol is developed that outlines the technical details of the emissions to be estimated and air quality modeling to be performed. The protocol documents the approach, procedures, participants, and other requirements needed to conduct photochemical grid modeling. This page provides references, tools, and reports that have been developed to support the RAQC’s ongoing emissions analysis and air quality modeling efforts.
For more information on air emissions modeling, please see EPA’s air emissions modeling, emissions inventories, and photochemical air quality modeling pages.
Ozone Attainment Forums
Forums are dedicated RAQC meetings where methodologies, analyses, and results related to technical modeling and analysis work needed to support the SIP process and attain the ozone standards are discussed in-depth. They cover a wide range of topics, from how the model is selected to how the model demonstrates the effects of local, regional, and international sources on ozone and how attainment is monitored. Below are references to forums previously conducted by the RAQC, with each forum link containing relevant documents and resources.
Registration is open at the link above; topics will be announced closer to the meeting date.
Topics Covered:
- Bump-up of the 2015 Ozone NAAQS Nonattainment Area to the Serious Classification
- 2024 Ozone Season Data Report and Planning Considerations
- Timeline and Milestones for Attainment Planning
- Status of technical work on Emissions and Modeling
Topics Covered:
- Draft Conceptual Model of Ozone Formation in the DM/NFR Non-attainment Area
- Emissions Inventory Improvements and Controls Presentation
- SIP Modeling Protocol
Topics Covered:
- Severe 75 ppb and Moderate 70 ppb SIP modeling – Results and Lessons Learned
- Emissions, Control Strategy, and Modeling Plans for the Serious 70 ppb SIP planning effort during 2024-25
Topics Covered:
- Methodology Outline: Denver Metro/North Front Range Oil and Gas Emission Inventory, May 10, 2023
- Revised Oil and Gas Emission Inventory Results
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- 2017 Oil and Gas Emission Inventory Spreadsheets, April 28,2023
- 2026 Oil and Gas Emission Inventory Spreadsheets, May 10, 2023
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- Severe SIP Modeling Plan
Topics Covered:
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- 2016 Modeling Platform Update since April 2021
- Analysis of 2020 and 2021 Meteorology
- 2023 and 2026 Design Value Projections
- Planned and Potential Sensitivity Analyses
Topics Covered:
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- 2016 Modeling Platform Update
- 2023 NOx/VOC Sensitivity Analysis
- 2023 Local Source Modeling
- 2023 International and Interstate Transport Analysis
Topics Covered:
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- Development of 2016 Base Case Modeling,
- 2020 and 2023 Future Year Modeling Projections
Topics Covered:
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- Overview of Modeling Sensitivities
- 2017 Local Source Apportionment Modeling
- Contribution of International Emissions on 2011 Base Case
- 2023 Ozone Projections and NOx/VOC Sensitivity
- FRAPPE and DISCOVER-AQ 2014 Regional Source Impacts
- Comparison of Oil and Gas Inventories with Monitored Ambient VOC Precursors
Topics Covered:
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- Development of 2008 Base Case Model
- Ozone Model Evaluation for the Denver 2008 Episode
Modeling Reports and Dashboards for 2026 Serious 70 ppb SIP Planning Efforts
The RAQC is conducting modeling efforts to aid in planning and SIP development efforts under the 2015 8-hour ozone Standards. Below are currently available reports and tools developed in support of this effort.
2022 DM/NFR Oil & Gas Emission Inventory: Expert Panel Review Summary (September 24, 2024)
Draft Final Conceptual Model of Ozone Formation – Denver Metro/North Front Range 2026 Serious Attainment Plan for the 2015 Ozone NAAQS and Appendix D – HySplit Plots (updated October 2024). The current review period for the Draft Final Conceptual Model is over and the document will be finalized in mid-2025 to support the Attainment Plan submittal at that time. Please direct any questions or comments to Tom Moore (tmoore@raqc.org).
Draft Final Modeling Protocol – Denver Metro/North Front Range 2025 Serious State Implementation Plan for the 2015 Ozone NAAQS (updated October 2024). The current review period for the Draft Final Modeling Protocol is over and the document will be finalized in mid-2025 to support the Attainment Plan submittal at that time. Please direct any questions or comments to Tom Moore (tmoore@raqc.org).
CSC Ozone Modeling and Analysis Plan Report Presentation, January 2024
2024-25 Serious 70 ppb SIP Modeling & Analysis Platform (MAP) Plan for the Denver Metro / North Front Range Ozone Nonattainment Area -December 2023
IWDW Denver Ozone Precursor WEP-AOI Potential Contribution Analysis Method – December 2023
Denver Metropolitan/North Front Range Nonattainment Area Emission Inventory Review, November 30, 2023
Potential Improvements to the Oil and Gas Emission Inventory for the Denver Metro/North Front Range Nonattainment Area, November 3, 2023
Modeling Reports and Dashboards for 2024 Severe 75 ppb SIP Planning Efforts
The RAQC is conducting modeling efforts to aid in planning and SIP development efforts under the 2008 8-hour ozone Standards. Below are currently available reports and tools developed in support of this effort.
IWDW Denver Ozone Precursor WEP-AOI Potential Contribution Analysis Method – December 2023
Denver Metro / North Front Range Nonattainment Area Oil & Gas Emission Inventory Final Report – for 2008 NAAQS Severe SIP modeling (Ramboll – July 2023)
Modeling Protocol Addendum for 2008 and 2015 Ozone Standards (Ramboll – June 2023)
Presentation of Draft SIP Elements – Attainment Demonstration (RAQC – May 2022)
Modeling Protocol for 2008 and 2015 Ozone Standards (Ramboll – May 2022)
Preliminary 2026 Future Year Modeling Results (RAQC – March 2022)
Modeling Protocol for 2008 and 2015 Ozone Standards (Ramboll – April 2019)
2023 Emissions Dashboard (Ramboll/Alpine – April 2021)
2023 NOx/VOC Sensitivity Analysis – Daily (Ramboll/Alpine – April 2021)
2023 NOx/VOC Sensitivity Analysis – Hourly (Ramboll/Alpine – April 2021)
2023 Local Source Apportionment Analysis (Ramboll/Alpine – April 2021)
2023 Transport Analysis (Ramboll/Alpine – April 2021)
Archived Reports and Presentations from Previous Planning Efforts
Reports and tools developed in support of prior modeling efforts are detailed below:
NOx/VOC Sensitivity Analysis (Ramboll/Alpine Geophysics – March 2018)
Source Apportionment Modeling Report (Ramboll – April 2017)
2017 Photochemical Grid Modeling – Model Performance Evaluation (Ramboll – September 2017)
2017 Photochemical Grid Modeling – Attainment Demonstration (Ramboll – September 2016)
Source Apportionment Modeling Analysis for the Denver Early Action Ozone Compact (Environ/Alpine Geophysics, May 2004)
Guidance Documents
Guidance documents from the EPA recommend steps to conduct modeling for ozone nonattainment areas. Generally, the guidance comes in two parts. The first part includes how to set up and apply a photochemical modeling platform, which includes meteorology, emissions, and air quality modeling. The second part describes how to use the modeling platform to project future year concentrations and demonstrate whether attainment of the standard is likely.
Requests for Proposals
The RAQC puts out requests for services from a consulting firm to aid in completing the modeling recommended under EPA guidance.