Potential Alternative to the Regional Haze Rule Visibility Progress Tracking Metric Used in the SIPs for the First Implementation Period

摘要

1. The Regional Haze Rule was promulgated in 1999 based on Clean Air Act sections 169A and 169B. 1.1 CAA declared the national goal of preventing future and remedying existing impairment of visibility in mandatory class Ⅰ Federal areas, which impairment results from man-made air pollution. 2. Regional haze is "visibility impairment that is caused by the emission of air pollutants from numerous sources located over a wide geographic area." 2.1 Visibility impairment means "any humanly perceptible change in visibility (light extinction, visual range, contrast, coloration) from that which would have existed under natural conditions". 3. Based on experiences during the first implementation period, EPA started working towards revisions to the rule and development of guidance for the second implementation period: 3.1 Proposed rule revisions on May 4, 2016 3.2 Announced draft guidance on July 8, 2016 3.3 Currently considering extensive public comments and working towards finalizing both later this year 4. In the proposed rule revisions, we proposed two options for tracking visibility in the second planning period: 4.1 Requiring all states to select the 20% worst days based on anthropogenic impairment. 4.2 Allow states to choose whether to select the 20% worst days based on anthropogenic impairment or continue to use the 20% haziest days.