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Source categories explained.
The CAA prescribes source category standards under the new source performance standards (NSPS) and national emissions standards for hazardous air pollutants (NESHAP) programs. Each standard is promulgated in its own subpart in 40 CFR Part 60 for NSPS and 40 CFR Part 63 for air toxics. Grandfathered pre-1990 NESHAP standards are in 40 CFR Part 61.
NSPS standards target criteria air pollutants and NESHAP standards target air toxics—sometimes covering the same source category. So, what is a source category?
For regulatory purposes, a source category defines a group of stationary sources that has the potential to emit a target pollutant. Intuitively, larger emitting stationary sources, like power plants and refineries, are source categories. But a source category can also be defined as specific equipment, such as a wastewater treatment plant, cooling tower, or volatile liquids storage tank. Ancillary equipment, such as piping and valves, is not typically named as a source category. However, it is often regulated under these standards as an affected source within a source category. Finally, a source category can be defined as a process (like chromium electroplating) or activity (like site remediation).
This broad method of defining source categories can make CAA compliance challenging. Any given plant or location may have several, sometimes overlapping, source categories. And learning how to identify what source category standards apply at a location is fundamental to CAA compliance. For more compliance morsels, visit our website.
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