EPA designated the Mendenhall Valley area of Juneau, Alaska as a moderate nonattainment area for the National Ambient Air Quality Standard (NAAQS) for particulate matter with an aerodynamic diameter less than or equal to 10 micrometers (PM10) in 1991 based on violations of the 24-hour PM10 standard that occurred throughout the 1980s. The EPA fully approved Alaska's moderate PM10 nonattainment area plan as a State Implementation Plan (SIP) revision for the Mendenhall Valley PM10 nonattainment area in 1994 (Federal Register: March 24, 1994). There have been no measured violations of the PM10 standard since 1994. EPA has approved a Limited Maintenance Plan (LMP) for the Mendenhall Valley area of Juneau that provides contingency plans if Juneau experiences a PM10 problem in the future. Juneau is designated as in attainment for PM10.
(Photo by Glynn Cater)