State Air Quality Plans

Under the Clean Air Act, states have the primary role of implementing programs to protect air quality in their jurisdictions. In some states, partial authority has been granted to local municipalities or counties, but that is not the case in Arkansas. Each state develops plans for implementing these programs that must be approved by the United States Environmental Protection Agency. There are two categories of state air quality plans: the state implementation plan and 111d state plans.

SIP Frequently Asked Questions (FAQs)

A state implementation plan or “SIP” is a compilation of state and/or local rules, statutes, non-regulatory provisions, quasi-regulatory measures, and other state-enforceable requirements that have been submitted to the United States Environmental Protection Agency (EPA), approved by EPA, and codified in the Code of Federal Regulations.

Arkansas’s SIP is codified at 40 CFR 52 Subpart E. Materials submitted for inclusion in the SIP are incorporated by reference into the Code of Federal Regulations as they exist on the date of EPA approval.

SIP is the framework by which a state implements its program to protect air quality, including for the attainment and maintenance of the national ambient air quality standards and for the protection of visibility in designated scenic areas.

No. Portions of APC&EC Rule 19 have been approved by EPA into the SIP. Certain Arkansas statutes, portions of APC&EC Regulation No. 26, and other DEQ-enforceable measures have also been approved into the SIP. These are incorporated by reference as in effect on the date that EPA approved the SIP revision containing the relevant provisions.

See 40 CFR 52 Subpart E for the current Arkansas SIP.

The state has the primary responsibility for enforcing the SIP. However, the EPA is authorized to take enforcement action for violations of the SIP.

In addition, members of the public can also file citizen suits under the Clean Air Act to address violations of SIPs.

If previously SIP-approved provisions are revised, a state must submit those revisions to EPA for approval if the changes are to be incorporated into the SIP. EPA may approve or disapprove the change based on whether the state adequately demonstrates that the change is consistent with Clean Air Act requirements. This process may take years. Until EPA approves these SIP revisions, the previously approved SIP requirements continue to be enforceable by EPA and under citizen suits even as the state enforces the changed requirements that are not yet approved by EPA. The SIP Gap is a term used to refer to the discrepancy between revisions to the SIP that have been submitted to EPA for approval and the SIP provisions as codified in the Code of Federal Regulations at any given time.


Any revision to the SIP is subject to public review for a minimum of 30 days. The public has the right to view materials proposed for inclusion in the SIP and provide comments for DEQ to consider prior to finalizing the proposed SIP revision. The public is also entitled to provide oral comments at a public hearing. Written comments are preferred in the interest of accuracy. DEQ must respond to comments received and explain its rationale in accepting or rejecting any suggested change to the proposed SIP revision.

DEQ often solicits public feedback before proposal of a SIP revision. This public engagement is in addition to any formal comment period on a proposed SIP revision. DEQ enforceable measures that may be included in a SIP—such as administrative orders, proposed new or amended rules, or permit modifications—are also subject to their own public period.

111d state plans provide for implementation of standards of performance for existing sources belonging to a stationary source category subject to new source performance standards (NSPS). NSPS promulgated by EPA apply to sources constructed or modified after a certain date. For those sources that were constructed prior to the NSPS date and that have not been modified since, states develop standards of performance pursuant to EPA guidelines. These standards of performance must reflect the application of the best system of emission reductions, as determined by EPA. Like SIPs, state plans are submitted to EPA for approval and are federally enforceable upon approval. State plans are also subject to the same public notice requirements as SIPs.

If a state does not submit a required SIP revision or 111d state plan by the designated deadline or if EPA disapproves a SIP revision or 111d state plan, EPA is required to promulgate a federal plan within two years of EPA issuance of a finding of failure to submit or disapproval unless the state submits and EPA approves a plan. States may also replace a federal plan if EPA approves a state plan or SIP. In addition, failure to submit an approvable SIP for attaining and maintaining the national ambient air quality standards may result in sanctions for the state. Failure to submit approvable 111d plans or visibility protection plans are not subject to sanctions.