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VISIBILITY ANALYSIS RECOMMENDATIONS

VISIBILITY ANALYSIS RECOMMENDATIONS. FEDERAL LAND MANAGERS’ AIR QUALITY RELATED VALUES WORKGROUP. “…methods for analyzing the impacts on visibility from new or modified air pollution sources.”. REGULATORY BASIS FOR RECOMMENDATION. National Goal (Clean Air Act Section 169A)

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VISIBILITY ANALYSIS RECOMMENDATIONS

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  1. VISIBILITY ANALYSIS RECOMMENDATIONS FEDERAL LAND MANAGERS’ AIR QUALITY RELATED VALUES WORKGROUP

  2. “…methods for analyzing the impacts on visibility from new or modified air pollution sources.”

  3. REGULATORY BASIS FOR RECOMMENDATION • National Goal (Clean Air Act Section 169A) • Sets goal as no manmade impairment • Definition of Visibility Impairment (40 CFR §51.301 (x)) • Sets natural conditions as the benchmark

  4. COMPONENTS OF THE RECOMMENDATION • Analysis Methodology (including a prescriptive outline) • Class I Area Specific Information • Identifies Thresholds • levels of concern • analysis thresholds • decision thresholds • Sample Application

  5. FUNDAMENTAL PRINCIPLE • New Sources (PSD and those subject to new source review) should not, by themselves, significantly impede progress toward the national visibility goal

  6. METHODOLOGY PROTOCOLS • Discrete Plumes (Near Field) • Sources within 50 km of the Class I Area • Visibility parameters • contrast • color difference (delta E) • Natural conditions as benchmark • VISCREEN, PLUVUE II

  7. PROTOCOLS (CONTINUED) • Aggregates of Discrete Plumes (Distant/multi-source) • Multiple Sources or Greater than 50 km from Class I Area • Visibility parameter • Extinction • Natural Conditions as Benchmark • CALPUFF

  8. PROTOCOLS (CONTINUED) • Cumulative Analyses of all new source growth Required under Some Conditions

  9. Near Field Screening |C|>=0.05 delta E >= 2 Refined |C| >= 0.02 delta E >= 1 Distant/Multi-source delta bext >=10% 10%  delta bext >=5% requires further analysis LEVELS OF CONCERN

  10. ANALYSIS THRESHOLDS • de minimis threshold for further analyses • 0.4% change in extinction (single source) • threshold for need for cumulative analyses • 5% change in extinction (single source) • if a cumulative analyses has already been done

  11. Near field Screening |C|< 0.05 delta E < 2 Refined |C|< 0.02 delta E < 1 Distant/Multi-source single source (S.S) < 0.4% cumulative delta bext >= 10% but S.S. delta bext < 0.4% DECISION THRESHOLDS

  12. SPECIFIC CLASS I AREA INFORMATION • Estimates of Natural Conditions • NAPAP East/West Estimates for Aerosol • By species • Non-hygroscopic components • Hygroscopic components • Extinction calculation algorithm • Rayleigh extinction • Site specific or interpolated relative humidity adjustment factors

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