While the CAA authorizes the EPA to set NAAQS, the states are responsible for establishing procedures to attain and maintain the standards. The states adopt plans known as State Implementation Plans (SIPs) and submit them to the EPA to ensure that they meet statutory requirements. SIPs are based on emission inventories and computer models to determine whether air quality violations will occur.
States must develop monitoring plans for air pollution levels; these may be funded by the EPA. If the SIP shows that standards may be exceeded, the state may be required to impose additional controls on existing sources. Proposed new and modified sources must obtain state construction permits in which the applicant has to show that anticipated emissions will not exceed allowable limits. Three years after EPA implements final NAAQS rule designations, states are required to submit SIPs to EPA that detail how areas will be brought into attainment.
EPA reviews the SIPs to determine their adequacy to meet statutory requirements and achieve attainment of the standards. If states do not meet the requirements of NAAQS, the federal government seeks to attain compliance in a number of ways. First, in nonattainment areas, emissions from new or modified sources must also be offset by reductions in emissions from existing sources.
Second, EPA can impose a 2-to-1 emissions within eighteen months for the construction of new polluting sources in states where the SIP is inadequate and can impose a ban on most federal highway grants six months later. An additional ban on air quality grants is discretionary, and ultimately, a Federal Implementation Plan may be imposed if the state fails to submit or implement an adequate SIP.