This final guidance revises the agency’s interpretation of when multiple air pollution-emitting activities are located on sufficiently “adjacent” properties to one another that they should be considered a single source for the purposes of permitting. To determine what activities comprise a single source under the NSR and Title V air permitting programs, three factors must be satisfied: the activities must be under common control; they must be located on contiguous or adjacent properties; and they must fall under the same major group standard industrial classification (SIC) code. In this guidance, for all industries other than oil and natural gas production and processing (for which there is a separate set of rules and to which this guidance does not apply), EPA adopts an interpretation of “adjacent” that is based on physical proximity only. The concept of “functional interrelatedness” would not be considered by EPA when determining whether activities are located on adjacent properties.

• "Adjacent" Guidance (PDF)(10 pp, 21 MB, November 26, 2019)