State Implementation Plan [1]

A requirement in the federal Clean Air Act [2] that places responsibility on individual states to develop programs that will ensure compliance with standards prescribed in the act.

To comply with provisions of the act, a state environmental agency begins by establishing geographical divisions within its jurisdiction: divisions referred to as Air Quality Control Regions (AQCRs). For each AQCR, the agency is then required to develop a specific plan, outlining the pollution control requirements for that region. In a metropolitan AQCR, for example, Stage II gasoline vapor control might be required. In a rural AQCR, it would not be.

These regional programs, adopted by a state, are referred to in the Clean Air Act as state implementation plans–SIPs.