Airshed characterizations were developed to provide a mid-scale air quality assessment in support of programmatic and project level land management planning processes. These airshed assessments were developed to serve as a consistent and systematic approach for evaluating air quality using common smoke management principles. Airshed assessments or characterizations are a compilation and synthesis of available emissions, monitoring, and climatology data applicable to air quality and smoke management. The assessments also summarize past burn information for wildfire and prescribed fire as well as provide an indication of future fire use workload using fire regimes. A primary consideration in developing the airshed assessments was to meet the intent of the EPA’s Interim Air Quality Policy on Wildland and Prescribed Fires. This included addressing planning elements and evaluating alternatives to burning.

The initial purpose and utilization of the airshed characterizations was to provide supporting analysis and technical documentation for the Southwest Idaho Ecogroup Land and Resource Management Plan (LRMP) revision of the Boise, Payette and Sawtooth National Forests. The combined administrated area of the three National Forests covers approximately 7 million acres in two states (Idaho and Utah) within 10 smoke management program airsheds. This area is further subdivided into numerous counties within the Ecogroup area of consideration. The area of consideration for the LRMP analysis was 100 kilometers from the administrative boundaries of the three Forests. This area encompassed over 40 counties in Idaho, Utah, Washington, Oregon, Montana and Nevada. Numerous sources of data were utilized to compile information at the airshed, forest and county levels. A Geographic Information System provided the means to spatially aggregate, calculate, and display data. This assessment also evaluated opportunities for alternative to burning and effects of land management allocation on these opportunities.