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Proposed PM 2.5 Calculation Methodology & Significance Thresholds

Proposed PM 2.5 Calculation Methodology & Significance Thresholds. South Coast Air Quality Management District Public Workshop August 9, 2006. PM 2.5 – Background. Primarily from combustion sources Mobile sources - auto, trucks Stationary sources – ICEs

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Proposed PM 2.5 Calculation Methodology & Significance Thresholds

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  1. Proposed PM 2.5 Calculation Methodology & Significance Thresholds South Coast Air Quality Management District Public Workshop August 9, 2006

  2. PM 2.5 – Background • Primarily from combustion sources • Mobile sources - auto, trucks • Stationary sources – ICEs • Directly emitted or formed in atmosphere from combustion of gases (such as NOx and SOx combining with ammonia) • Focus is on directly emitted PM2.5

  3. PM2.5 Air Quality

  4. Trends of Basin PM2.5 (µg/m3)

  5. Ambient Air Quality Standards • Federal PM 2.5 standards established in 1997 • State PM 2.5 standards established in 2002 • AQMD & CEQA significance thresholds for directly emitted PM2.5 yet to be developed • Proposed actions • PM2.5 calculation methodology • Regional & localized significance thresholds

  6. PM2.5 Emission Calculation Methodology • Calculate PM10 using standard methodologies and PM10 emission factors • Apply CARB’s PM2.5 fraction profiles by source category as default • CARB’s profiles used for AQMP inventories with public review process • Project-specific PM2.5 profiles acceptable

  7. Significance Thresholds – Approaches • No backsliding from PM10 thresholds • PM2.5 thresholds must be at least as stringent as PM10 thresholds • PM10 thresholds were used as a basis to develop PM2.5 thresholds • Reflects air quality & source emissions • Considers current nonattainment status of district & PM2.5 emission reductions necessary to demonstrate attainment • Considers emission source type, e.g., fugitive vs. combustion emissions

  8. Proposed Localized Significance Thresholds (LSTs) • LSTs – Construction = 10.4 µg/m3 • Same as PM10 construction LST • ~75% - 100% of emissions contributed from construction equipment engine exhaust depending on construction phase • More stringent than PM10 LST • Will prepare LST look-up tables for projects one through five acres in size

  9. Proposed LSTs (Cont.) • LST – Operation = 2.5 µg/m3 • Same as PM10 operation LST • ~99% of PM10 combustion emissions are PM2.5 • Will prepare LST look-up tables for projects one through five acres in size

  10. Proposed Regional Significance Thresholds (RST) • PM2.5 RST – Operation & Construction = 55 #/day • PM2.5 emissions • Primarily from combustion • PM2.5 suspended for longer periods resulting in regional effects • EPA proposed significant emission rate of 10 tons per year for PM2.5 (Federal Register, Sept 8, 2005) • Recommend daily construction and operational PM2.5 RST consistent with EPA proposal

  11. Next Steps • Recommendations to Governing Board October 6, 2006 • Effective Dates: • Begin public outreach after Board approval • Begin IGR commenting for NOPs/ISs 1/2007 • Implement for new AQMD lead agency projects after Board approval • Highlight PM2.5 mitigation measures on AQMD CEQA webpages by 10/06

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