EPA has issued a final rule under the New Source Review (NSR) program that revises the agency’s policy on “aggregation.” For the purpose of determining whether NSR applies, a facility should group together, or aggregate, emissions from multiple related changes into one single project, only if those activities are substantially related.

This rule directs facilities and permitting authorities to combine emissions from plant modifications only when those activities are substantially related.

In addition, the final rule specifies that for emissions to be aggregated, changes must have more in common than timing alone or just supporting the plant’s overall basic function; and plant modifications that are separated by three or more years will be presumed not to be substantially related.

This final rule establishes EPA policy prospectively. It finalizes one of three parts of a September 2006 proposal. EPA is withdrawing the options for “debottlenecking” that were included in the proposed rule and is taking no action on the proposal that would enable emissions decreases to be factored into the first part of the test used to determine whether NSR applies to a facility making a change.

NSR is a preconstruction permitting program to ensure air quality is maintained when factories, industrial boilers and power plants are built or modified. The program ensures that state-of-the art emission control technology is installed at new plants or existing plants that are undergoing a major modification.