Air Quality Management - State Implementation Plans (SIPs)

The State Implementation Plan defines the combination of local, state and federal actions and emissions control needed for an area to meet ambient air quality standards and for an area that has attained the NAAQS to maintain compliance and prevent significant deterioration (PSD) of air quality. The first step in developing a SIP is to divide the state into geographical regions known as Air Quality Control Regions (AQCRs). An AQCR could be a metropolitan area or a county. Using the AQCRs for management purposes, the states could devise their own requirements for controlling air pollution related to specific local needs. This could include the control of both new and existing sources of air pollution. An example of a common measure taken by states within their SIPs is the requirement that all motor vehicles be regularly inspected and tested for air emissions control.

The SIP is developed by state and local officials, but must be approved by EPA. Once approved, it becomes legally enforceable on both the state and federal levels. If all or part of a SIP is not approved, EPA assumes responsibility for developing an appropriate plan. To supplement the SIPs, federal regulatory and support programs are also in place. In one support program, EPA establishes control techniques guidelines (CTG) for controlling air pollutants for specific industries. These CTGs provide states with information on existing control technologies referred to as reasonably available control technology (RACT). RACT represents control techniques commonly in use in a specific industry. To date, EPA has promulgated over 60 CTGs. (Air Quality Management in the United States, Report of The National Research Council, 2004). On the other hand; a regulatory program that supplements the SIPs is the New Source Performance Standard (NSPS).