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9 

 stakeholders to participate in all the meetings, analyses, and 

 reviews, are not equal. Nevertheless, the Commission provides the 

 States in the region an opportunity to contribute valuable 

 information and recommendations to EPA. Under the Clean Air Act, 

 the ultimate responsibility for effectuating the visibility 

 protection provisions remains with EPA. 



We have strongly recommended to the Grand Canyon Visibility 

 Transport Commission that it streamline its work plan and 

 assessment by relying to the fullest extent possible on the 

 excellent work performed by the National Research Council of the 

 National Academy of Sciences in its 1993 report on Protecting 

 Visibility in National Park and Wilderness Areas (NRC Report) . The 

 NRC Report notes that visibility — "the ability to look out over 

 great vistas to see shapes and colors with crystalline clarity" — is 

 "at the heart" of the park and wilderness experience. The NRC 

 Report confirms the fragility of the visibility resource as well as 

 its seriously damaged state, with average annual visual range in 

 the West diminished to about one-half to two-thirds of natural 

 visual range, and average annual visual range in the East 

 diminished to about one-fifth of natural. 



The NRC Report states that "visibility impairment is probably 

 better understood and more easily measured than any other air 

 pollution effect." The NRC Report notes the lack of progress in 

 implementing Clean Air Act programs to protect visibility and 



