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Consequence Analysis

Consequence Analysis. Robert Wu South Coast Air Quality Management District. South Coast Air Quality Management District. ~ 15 Million People ~ 10,000 square miles ~ 10 Million Vehicles ~ 27,000 Permitted Facilities (60,000+ Permits) Stagnant Weather Patterns

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Consequence Analysis

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  1. Consequence Analysis Robert Wu South Coast Air Quality Management District

  2. South CoastAir Quality Management District • ~ 15 Million People • ~ 10,000 square miles • ~ 10 Million Vehicles • ~ 27,000 Permitted Facilities (60,000+ Permits) • Stagnant Weather Patterns • Nation’s Most Severe Air Pollution

  3. Methods for the Consequence Analysis • Develop set of matched pairs of meteorological sites. • Run ISCST3 with 1981 AQMD met data. • Run AERMOD with 2005-2007 met data developed by EnviroComp. • Concentration data placed in Access database. • Calculate AERMOD-to-ISCST3 ratios of peak predicted concentrations and segregate results. • by dispersion characteristics (i.e., rural or urban) • by source type • by averaging time • by meteorological site

  4. Source Receptor Areas within the South Coast Air Basin

  5. Locations of Available Monitoring Stations

  6. Meteorological Site Pairs

  7. Comparison of Mean Wind Speeds1981 vs. 2005-2007

  8. Comparison of Light Wind Frequencies1981 vs. 2005-2007

  9. Simulation Comparisons • Dispersion characteristics • Rural & urban • Source Types • 8 point sources, 5 volume sources, & 5 area sources • Averaging times • 1-hr, 3-hr, 8-hr, 24-hr, & period • Meteorological site • 20 pairs

  10. Point Sources

  11. Volume Sources

  12. Area Sources

  13. Overall Results

  14. Distribution of Results

  15. Results by Source Type

  16. Distribution of Results for Point Sources

  17. Results by Averaging Period

  18. Results by Meteorological Site

  19. Results by Meteorological Site

  20. Conclusions • Average wind speeds and frequencies of light winds are similar for the 1981 and the 2005-07 meteorological data. • 1981 data has slightly lower average winds and a somewhat greater frequency of light winds. • Under urban dispersion conditions, ISCST3 and AERMOD yield similar peak concentrations for all source types, all averaging periods, and at all the meteorological sites.

  21. Conclusions (continued) • Under rural dispersion conditions, AERMOD yields significantly higher peak concentrations for point and area source types, all averaging periods, and all meteorological sites. • AERMOD-to-ISCST3 ratios are highest for point sources and for longer averaging times (i.e., 24-hour and annual concentrations).

  22. AERMOD Website • Go to www.aqmd.gov • Community • Air Quality • Historical Data • Meteorological Data • Both ISCST3 and AERMOD meteorological data sets are available for download and use.

  23. AERMOD – Options • Use regulatory default and urban option. • Include terrain and building downwash • For maximum annual concentrations of criteria pollutants, each calendar year must be analyzed separately. • For cancer risk and chronic HI, use the entire 3-year data set in the analysis.

  24. AERMOD - Implementation • Rule 1303 and Rule 2005 • All permit applications received on or after September 1, 2009 must use AERMOD • Rule 1401 • Tier 3 analyses in all permit applications received on or after September 1, 2009 must use AERMOD • Tier 4 analyses using HARP, either ISCST3 or AERMOD (use HARP On-Ramp to generate HARP files) can be used.

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