Designation of Areas for Air Quality Planning Purposes: State of Idaho and the Fort Hall Indian Reservation

In this action, the Environmental Protection Agency (EPA) is revising the designation for particulate matter with an aerodynamic diameter of less than a nominal 10 microns (PM-10) for the Power- Bannock Counties PM-10 nonattainment area, located in Idaho, by creating two distinct nonattainment areas that together cover the identical geographic area as the original nonattainment area. The revised areas are divided at the boundary between State lands and the Fort Hall Indian Reservation, with one revised area consisting of State lands and the other revised area consisting of lands within the exterior boundaries of the Fort Hall Indian Reservation. The redesignation is based upon a request from the State of Idaho, which is supported by monitoring and modeling information. Both areas retain PM- 10 nonattainment designation and classification as moderate PM-10 nonattainment areas as a result of this action. EPA recently established a new standard for particulate matter with an aerodynamic diameter equal to or less than a nominal 2.5 microns and also revised the existing PM-10 standards. This rule, however, does not address these new and revised standards.