Document Archives Reports

4th Maximum Ozone Values Table (ppb) through September 30th, 2017

Posted Under: News Room - News, Ozone (8-Hour Standard)

Click here to view current table

The Denver Metro/North Front Range area is designated as nonattainment by the U.S. Environmental Protection Agency (EPA) for the pollutant ozone. The 2008 8-Hour Ozone Standard is 75 parts per billion (ppb) and is calculated using a rolling three-year average of the fourth (4th) highest daily 8-hour ozone concentration.

The table linked above shows current monitoring data for the nonattainment area, including the top four (4) values for each monitoring site for the current ozone season as well as the 4th highest values for the previous two years. The 4th highest values over a three-year period are averaged to determine the Design Value (DV) at each monitor. The highest DV is the test of attainment, with all monitors having to be at or below the standard.

The RAQC’s ozone education campaign, Simple Steps. Better Air., issues Ozone Action Alerts as well as notices about upcoming community events. The public is encouraged to participate in efforts to reduce air pollution by joining the Clean Air Community and using the OzoMeter to track air quality impacts.

For additional information on ground-level ozone, please visit or call (303) 629-5450, ext. 220.

Click here to view previous tables

2017 Source Apportionment Modeling Report Available

Posted Under: Modeling, Modeling, Modeling & Emissions Inventories, News Room - News, Ozone


As part of future ozone planning for the Denver Metro/North Front Range (DM/NFR) nonattainment area, the Regional Air Quality Council (RAQC) and Air Pollution Control Division (APCD) recently completed a report on ozone source apportionment modeling for the 2017 emissions year using the 2011 modeling database developed for the Moderate Area Ozone State Implementation Plan (SIP).  The report detailing this modeling effort is now available on the RAQC website (Denver/North Front Range Local Source 2017 Source Apportionment Modeling Using a 2011 Modeling Database).

In addition to the report, modeling results have been loaded into a Source Apportionment Visualization Tool (SA Vis Tool) that can be accessed through the Intermountain West Data Warehouse (IWDW).  Through this tool, users can isolate individuals monitors to see the source contributions on individual days and averaged over multiple days.

Beyond this modeling effort, the RAQC and APCD are also in the process of conducting sensitivity modeling that includes evaluation of:

  • 2023 future year modeling based on on-the-books reductions
  • Impact of both intrastate emissions controls outside Colorado and contributions of international emissions
  • Impact of broad Nitrogen Oxides (NOx) and/or Volatile Organic Compound (VOC) reductions at monitors in the DM/NFR nonattainment area

Upon completion of these sensitivity runs, the RAQC and APCD will be hosting a modeling forum to present results and discuss how the analyses play into future ozone planning efforts.

Please feel free to contact Amanda Brimmer, RAQC,  with any questions or comments.

Attainment Demonstration Modeling for the Denver Metro/North Front Range 2017 8-Hour Ozone State Implementation Plan (SIP) – Draft Modeling Protocol

Posted Under: Modeling, News Room - News


The RAQC is in the process of conducting modeling needed to demonstrate attainment of the current March 2008 ozone National Ambient Air Quality Standard (NAAQS) in Denver Metro/North Front Range region by 2017.  This Modeling Protocol guides the technical details of a modeling study and provides a formal framework within which the scientific assumptions, operational details, commitments and expectations of the various participants can be set forth explicitly and means for resolution of potential differences of technical and policy opinion can be worked out openly and within prescribed time and budget constraints.  Current modeling is being carried out by a contracting team consisting of Ramboll Environ US Corporation and Alpine Geophysics, LLC under contract to the Regional Air Quality Council (RAQC).

Click here to access.