Publication Summary

The federal strategy for visibility protection called for a two phased effort. Phase I was designed to deal with visibility impairment in mandatory Class 1 federal areas that is easily attributable to distinct plumes from large stationary sources or groups of stationary sources (often called "plume blight"). The control strategies found in the current Washington State Visibility SIP target these kinds of sources and prescribed burning. Although prescribed forestry burning is not considered a stationary source, Washington's phase I Visibility SIP addresses this source because of the significant attributable contribution to impacts from prescribed burn plumes. Phase II regulations are designed to deal with visibility impairment resulting from regional haze, the wide spread impairment of visibility from the combined emissions of all sources including mobile area, small stationary sources and urban plumes. Development of phase II visibility protection regulations was forestalled until the scientific and technical limitations to understanding regional haze were overcome.