New Air Permitting Requirements Finalized for Class I Areas

Issued in December 2000, the Federal Land Managers' Air Quality Related Values Work Group (FLAG) Phase I report set new visibility requirements and adjusted air dispersion modeling values, presenting new challenges for facilities near Class I areas. The report resulted from an interagency work group comprised of U.S. Fish and Wildlife Service, National Parks Service, and United States Department of Agriculture Forestry Service personnel (collectively known as Federal Land Managers or FLMs). The over-arching goal of the FLAG guidelines is to standardize requirements among FLMs, who are responsible for maintaining air quality in federally protected areas. One of the most dramatic guideline changes issued in the Phase I report is the new visual range value. While the method of analysis remains unchanged, with a five percent degradation allowed for a single facility or a total ten percent degradation for all facilities, the revised background visual range results in a much more stringent analysis. Prior estimates of visual range were based in the 90th percentile cleanest measured day. The revised FLAG document instead uses estimates of natural conditions derived from the 1990 National Acid Rain Precipitation Assessment Program (NAPAP) studies, which determined natural conditions as an essentially 'pre-industrial' environment. The revised visual range is two to five times more stringent than the older values. Phase I also impacts air dispersion modeling, moving the relative humidity f (RH) function cutoff from 95 percent to 98 percent. Change in visibility increases as relative humidity increases, and these data are critical for air dispersion modeling of Class I areas. Previously, if the relative humidity rose above 95 percent, one could calculate potential change in visibility at the 95 percent threshold. The final Phase I report has raised this function cutoff to 98 percent, creating a more strict analysis since greater visibility degradation must now be considered for higher relative humidity values. Phase II of the FLAG report will address complex issues, requiring additional data to fill information gaps identified in Phase I. Potential Phase II developments include recommending methods for establishing critical loads of pollutants, recommending a policy on re-designation of Class II federal lands to Class I, and refining procedures for cumulative AQRV impacts analyses. FLAG Project Manager John Bunyan said that the workgroup cannot yet indicate when a draft of the Phase II report will be available.

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