Prevention of Significant Deterioration Baseline Dates

Contact: Stephanie Hengesbach, 517-648-7015
Agency: Environment, Great Lakes, and Energy

When modeling to demonstrate compliance with the Prevention of Significant Deterioration (PSD) increments, it is necessary to include all PSD increment consuming sources in addition to the proposed source. All post-baseline sources emitting SO2, NO2, PM10, or PM2.5 are considered to consume increment whether or not their emission rates exceed EPA's de minimus ton per year levels. To determine whether or not an existing source consumes increment it is necessary to know the applicable baseline dates. There are two types of baseline dates: major source and minor source.

The major source baseline dates are fixed dates identified in the 1977 Clean Air Act for each of the three pollutants. Emissions associated with a modification at a major stationary source consume increment after this date.

The minor source baseline date was set by the first completed PSD application received by the Air Quality Division. Emission changes at all sources after this date affect the increment. For this reason, it is commonly referred to as the "baseline date." It is possible to expand the available increment if a post-baseline source is to reduce or eliminate the emissions of the pollutant. Minor source baseline dates are established for different areas of the state called Air Quality Control Regions (AQCRs). Note that AQCR 123 has a separate area for which PM10 has an alternate baseline date.