EPA proposes changes to once-in, always-in policy for MACT standards.

The U.S. Environmental Protection Agency (EPA) has proposed changing when and how major sources of hazardous air pollutants (HAPs) can change their status to a minor, or area, source. The proposed amendment to the General Provisions of the National Emission Standards for Hazardous Air Pollutant was published in the Federal Register on Jan. 3, 2007.

Section 112 of the Clean Air Act requires EPA to issue national emissions standards for major sources of 187 listed HAPs. Major sources are those that emit more than 10 tons per year of a listed HAP or 25 tons or more per year of a combination of HAPs. EPA is required to base emissions limits on maximum achievable control technology (MACT), defined as the average of the best-performing 12% of sources.

Currently, EPA requires all sources to certify whether they are a major or area source by the first compliance date, then maintains a once-in, always-in policy for compliance monitoring. If finalized, the amendment would reverse the current once-in, always-in policy by allowing sources to change status at any point by reducing its emissions below the major source threshold.

For more information on the rule, visit http://www.epa.gov/ttn/oarpg/t3/ fact_sheets/OIAIpropfs.html.