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The Department periodically analyzes the monitored concentrations across the state to determine the background concentrations that should be added to dispersion modeling results for comparison to the National Ambient Air Quality Standards (NAAQS).
Background Concentration Value
Rolling 3-month average
This data is intended for use in non-PSD 24-hour PM2.5 modeling analyses conducted using the 2005-2009 meteorological datasets maintained by the Department. The data is formatted for use in the AERMOD dispersion model and is specific to certain areas of the state. Refer to the map shown below and choose the data that matches the location being modeled.
This data is intended for use in 1-hour NO2 modeling analyses when the non-regulatory default Tier 3 Ozone Limiting Method (OLM) or Plume Volume Molar Ration Method (PVMRM) is utilized in the AERMOD dispersion model. OLM and PVMRM are screening methods used to convert NO to NO2. The background ozone concentration is one of the key inputs for use of OLM and PVMRM. The Department has generated a background ozone concentration file for use anywhere in the state for the time period coinciding with the 2005-2009 meteorological dataset. The file provided below is a combination of the ozone monitor data collected from 12 sites across the state. Due to the non-regulatory status of OLM and PVMRM prior approval from DNR is required when either will be used. This ozone data is pre-approved for all such requests that will utilize the Department's 2005-2009 meteorological data.