§ 81.300 Scope.

(a) Attainment status designations as approved or designated by the Environmental Protection Agency (EPA) pursuant to section 107 of the CAA are listed in this subpart. Area designations are subject to revision whenever sufficient data become available to warrant a redesignation. Both the state and EPA can initiate changes to these designations, but any state redesignation request must be submitted to EPA for concurrence. The EPA has replaced the national ambient air quality standards for particulate matter measured as total suspended particulate with standards measured as particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM-10). Accordingly, area designations for PM-10 are included in the lists in subpart C of this part. However, the TSP area designations will also remain in effect until the Administrator determines that the designations are no longer necessary for implementing the maximum allowable increases in concentrations of particulate matter pursuant to section 163(b) of the CAA, as explained in paragraph (b) of this section. The EPA has also added national ambient air quality standards for fine particulate matter measured as particulate matter with an aerodynamic diameter less than or equal to a nominal 2.5 micrometers (PM_2.5). Accordingly, area designations for PM_2.5 are included in the lists in subpart C of this part.

(b) Designated areas which are listed below as attainment (“Better than national standards”) or unclassifiable (“Cannot be classified”) for total suspended particulate (TSP), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂), represent potential baseline areas or portions of baseline areas which are used in determining compliance with maximum allowable increases (increments) in concentrations of the respective pollutants for the prevention of significant deterioration of air quality (PSD). With respect to areas identified as “Rest of State” it should be assumed that such reference comprises a single area designation for PSD baseline area purposes. However, for PM-10, the use of the term “Rest of State” is an interim measure to designate as unclassifiable all locations not originally designated nonattainment for PM-10 in accordance with section 107(d)(4)(B) of the Act.

(c) For PM-10 areas designated nonattainment, pursuant to section 107(d)(4)(b) by operation of law upon enactment of the 1990 Amendments to the Act, the boundaries are more fully described as follows:

(1) For cities and towns, the boundary of the nonattainment area is defined by the municipal boundary limits as of November 15, 1990, the date the 1990 Amendments were signed into law, except for areas which were formerly categorized as “Group I areas”, in which case the nonattainment area is defined by the municipal boundary limits as of October 31, 1990.