Section 204.220  Adverse Impact on Visibility

"Adverse impact on visibility" means visibility impairment that interferes with the management, protection, preservation or enjoyment of the visitor's visual experience of the Federal Class I area.  This determination must be made on a case-by-case basis taking into account the geographic extent, intensity, duration, frequency and time of visibility impairment, and how these factors correlate with:

a)         Times of visitor use of the Federal Class I area; and

b)         Frequency and timing of natural conditions that reduce visibility.