State Implementation Plan in the United States

State Implementation Plan (SIP) in Environmental Law

A state plan for regulating air pollution required by the Clean Air Act to ensure that states meet the National Ambient Air Quality Standards. The Environmental Protection Agency (EPA) establishes limits for air pollutants that it determines must be controlled to protect human health and the environment. States are then required to prepare a state implementation plan outlining how the state will achieve the standards. State implementation plans must be at least as stringent as any part of the statute or any regulations the EPA has published. The state must have legislative authority to handle the administrative aspects of the air control program, and it must have the right to enforce its law.

Over the past twenty years or so, guidance has become more detailed on what must be included in the SIP. At first the guidance came primarily from the EPA, but Congress stepped in in 1990 when it amended the Clean Air Act, and requirements can be found both in regulations and the statute itself.

After the SIP is prepared, it must be submitted to the EPA, which will decide whether it meets the conditions for approval. The EPA may approve or disapprove the SIP; it may approve only part of the state plan, disapprove part, or request further revisions. Until it is approved by the EPA, it is state law only and can only be enforced by the state. After approval, it becomes federal law as well, and either the EPA or the state can enforce it. If the state involved does not submit an approvable plan within the time specified by the EPA or Congress, a federal implementation plan will be prepared by the EPA.

States may revise their SIPs as they wish, but any changes must be submitted to the EPA. The EPA has power to force amendments to the SIP if it decides that the plan is no longer adequate or does not include necessary changes reflecting federal law. This action by the EPA is labeled an SIP call. If the EPA issues regulations for a newly listed pollutant, the states must revise their state implementation plans to incorporate the new criteria. Congress may also specify as it did in 1990 that amendments to the SIPs must be made to conform with the statute.

Even though a state cannot have a SIP that allows more air pollution than federal law does, it is permitted to include measures that will result in better control of air pollution. Most SIPs tend to follow federal law, though, sometimes by incorporating federal regulations almost verbatim. However, a state may choose to go beyond those standards.
Based on “Environment and the Law. A Dictionary”.