VISIBILITY ANALYSIS RECOMMENDATIONS

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VISIBILITY ANALYSIS RECOMMENDATIONS

• FEDERAL LAND MANAGERS AIR QUALITY RELATED VALUES
  WORKGROUP

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methods for analyzing the impacts on visibility
from new or modified air pollution sources.
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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

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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

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FUNDAMENTAL PRINCIPLE

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

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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

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PROTOCOLS (CONTINUED)

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

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PROTOCOLS (CONTINUED)

• Cumulative Analyses of all new source growth
  Required under Some Conditions

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LEVELS OF CONCERN

• Distant/Multi-source
• delta bext gt10
• 10 ? delta bext gt5
• requires further analysis

• Near Field
• Screening
• Cgt0.05
• delta E gt 2
• Refined
• C gt 0.02
• delta E gt 1

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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

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DECISION THRESHOLDS

• Distant/Multi-source
• single source (S.S) lt 0.4
• cumulative delta bext gt 10 but S.S. delta bext
  lt 0.4

• Near field
• Screening
• Clt 0.05
• delta E lt 2
• Refined
• Clt 0.02
• delta E lt 1

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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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