Guidance for Tracking Progress Under the Regional Haze Rule
This document provides guidance to EPA Regional, State, and Tribal air quality management authorities and the general public, on implementing Clean Air Act provisions and EPA regulations, concerning the tracking of progress under the regional haze program. The guidance is designed to implement national policy on these issues. Sections 169A and 169B of the Clean Air Act (42) U.S.C. § § 7491,7492 and implementing regulations at 40 CFR 51.308 and 51.309 contain legally binding requirements. This document does not substitute for those provisions or regulations, nor is it a regulation itself.
Although much of the information in this guidance document is still relevant to the regional haze program, several of the recommendations have been updated in the 2018 Technical Guidance on Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program. Updates include: methods for 1) selecting the 20 percent most impaired days to track visibility and determining natural visibility conditions and 2) accounting for international impacts to adjust the uniform rate of progress. Additionally, the 2020 Memo and Technical Addendum on Ambient Data Usage and Completeness for the Regional Haze Program clarifies recommendations for ambient data completeness criteria and the use of patched and substituted data.
