The purpose of this March 2016 memorandum is to provide information to the Environmental Protection Agency Regional offices and the states as they develop and review state implementation plans (SIPs) that address the interstate transport provision of the Clean Air Act (CAA) section 110(a)(2)(D)(i)(I), otherwise known as the "Good Neighbor" provision, as it pertains to the 2012 fine particulate matter (PM_2.5) National Ambient Air Quality Standards (NAAQS).

This memo provides future year annual PM_2.5 design values for monitors in the United States based on quality assured and certified ambient monitoring data and air quality modeling. The memo further describes how these projected potential design values can be used to help determine which monitors (i.e., receptors) should be further evaluated to potentially address if emissions from other states significantly contribute to nonattainment or interfere with maintenance of the PM_2.5 NAAQS at these monitoring sites. This memorandum consists of:

• a description of the framework that has been previously used to address the good neighbor provision, and

• the EPA's review of relevant modeling data and air quality projections as they relate to this NAAQS.

This memorandum also contains two attachments with more details on the base and future year EPA modeling. The full set of base and future year 2012 PM_2.5 NAAQS design values for all sites can be found in Attachment 2.

• Information on the Interstate Transport "Good Neighbor" Provision for the 2012 Fine Particulate Matter National Ambient Air Quality Standards under the Clean Air Act Section 110 (a)(2)(D)(i)(I) (PDF)(24 pp, 10 MB, March 17 2016)
  Information for regions and states as they develop and review SIPs that address interstate transport.