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certain air emission levels and install the best available 

 control technologies. However, because PSD requirements relate 

 to the construction of facilities, they do not affect facilities 

 built prior to 1977, unless these facilities undergo major 

 modification. Furthermore, PSD requirements do not apply to many 

 minor sources whose cumulative emissions are believed to 

 adversely impact visibility in class I areas. 



In our 1990 report, we found that only 1 percent of the 

 sources near the class I areas we looked at were subject to PSD 

 requirements; 99 percent were exempt. Moreover, these exempt 

 sources account for a significant portion of the air pollutants 

 emitted near class I areas. For example, in the Shenandoah 

 National Park approximately 98 percent of the sulfur dioxides and 

 87 percent of nitrogen oxides--two of the primary contributors to 

 visibility impairment—emitted near the Park in 1992 came from 

 exempt facilities. 



Concerned that existing sources not subject to PSD 

 requirements may be major contributors to visibility impairment 

 in class I areas, EPA's Assistant Administrator for Air and 

 Radiation established a workgroup in November 1993 to examine 

 this issue. While workgroup members agree that significant 

 visibility problems in class I areas are directly attributable to 

 existing sources, they have not reached a consensus on how best 

 to solve the problem. 



Park Service Has Influenced 

 Emission Levels For New Facilities 



Although the scope of the PSD program is not sufficiently 

 inclusive, it is nevertheless working somewhat better than when 

 we reported to you in 1990, specifically, with regard to the Park 

 Service's role in reviewing permit applications. One of the 

 problems with the PSD program that we reported to you in 1990 was 



