However, these standards remain in effect until one year after an area is designated for the 2010 standard, except in areas designated nonattainment for the 1971 standards, where the 1971 standards remain in effect until implementation plans to attain or maintain the 2010 standard are approved. 

## 2.2.2. Attainment/Nonattainment Areas 

Within two years of promulgating a NAAQS, EPA must work with state and local governance to designate areas as either meeting or not meeting the NAAQS based on the most available air monitoring data. Areas possessing monitored outdoor air concentrations within the NAAQS are considered “Attainment” areas; areas possessing outdoor air concentrations excess of the NAAQS are considered “Nonattainment”. Once a nonattainment area meets the NAAQS and additional redesignation requirements in the CAA 6 , EPA will designate the area as a " Maintenance area." (See Section 8 , Conformity, for more information attainment/nonattainment areas.) 

## 2.2.3. State Implementation Plans 

The State Implementation Plan (SIP) is a collection of air quality measurements, modeling, regulations, controls, programs, and other measures used to identify air quality issues and to remedy or prevent violations of the NAAQS. Within three years of the promulgation of NAAQS, states must submit an “Infrastructure SIP” to EPA regardless of whether or not there are any designated nonattainment or maintenance areas in their jurisdiction. The purpose of the Infrastructure SIP is to demonstrate that a state has the legal authority, regulatory structure , and necessary resources to implement and enforce the NAAQS as required by the CAA. 

Additional types of SIPs are required for nonattainment and maintenance areas and include the following (as applicable): 

• Attainment Demonstration – Contains ambient monitoring, emissions inventory, modeling, and proposed control strategies for the initial year, int erim year(s), and attainment year as established by the CAA supporting a demonstration to EPA that the NAAQS will be attained by CAA-required deadlines; 

• Control/Program SIP – Documents the initiation or revision of specific control measures necessary to demonstrate attainment or otherwise show CAA compliance (e.g., vehicle inspection/maintenance programs, fee programs, and reasonably-available control technologies); 

• Maintenance Plan – Once a nonattainment area attains and continues to attain NAAQS for three years, a maintenance plan is required to show EPA that the NAAQS will be attained for a period of 10 to 20 years; and 

• Milestone/Progress SIP – Also known as Rate of Progress or Reasonable Progress Plans (ROP/RFP), these are only required for certain O$_{3 }$ nonattainment areas, showing that plans and controls designed to attain the NAAQS will nonattainment area emissions by at least 15 percent in the first six years and by 9 percent every three years thereafter until the standard is attained. 

