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Defining “Significant Impact” from Mobile Sources and Road Dust

Defining “Significant Impact” from Mobile Sources and Road Dust. By John F. Kowalczyk Co-Chair WRAP Mobile Source Forum WRAP Board Meeting July 24, 2002. “Significant Impact” Requirements in Section 309.

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Defining “Significant Impact” from Mobile Sources and Road Dust

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  1. Defining “Significant Impact” from Mobile Sources and Road Dust By John F. Kowalczyk Co-Chair WRAP Mobile Source Forum WRAP Board Meeting July 24, 2002

  2. “Significant Impact” Requirements in Section 309 • Determine if Mobile Source Emissions or Road Dust “Contribute Significantly” to Visibility Impairment in any of the 16 Class I areas on the Colorado Plateau based on Current and Projected Levels.

  3. Definitions • Mobile Sources include On-Road and Non-Road Engine, Evaporative and Tire and Brake Wear Emissions • Road Dust includes Paved and Unpaved • Analyze Mobile Impacts from Major Urban Areas • Analyze Road Dust Impacts from State/Reservation

  4. If Mobile Source are a “Significant Contributor” • Requires State to Restrict Emissions to Projected Lowest Levels • Implement Measures to Achieve “Emissions Budget” and Demonstrate Compliance • Establish Emission Tracking System • Separate from Conformity according to EPA

  5. If Road Dust is a “Significant Contributor” • Must Implement “Necessary and Appropriate Emission Management Strategies”

  6. Questions • “Significant” Not Defined • “Areas of State” Not Defined • What to do about Inaccuracies in Modeling Road Dust

  7. Mobile Source Forum “Preliminary Recommendations” • Three Alternative Definitions of “Significant” • Evaluate Alternatives against Modeling Results for Realisticness and Reasonableness • Choose Alternative or Revise and make Final Recommendation (Expect by end of Summer) • Consensus on Other Issues

  8. Alternative” Significant Contribution” Definitions • Cumulative< 1 DV Significance ~ 0.5 DV Cumulative >1DV Significance ~ 0.1 DV • Significance ~ 1.0DV • Significance ~0.1 DV

  9. Alternative 1 Definition of “Significant” • Two Tier “Significance” Level Based on Cumulative Impact from all 9 States • Cumulative Approach based on some Consistency with PSD/NSR and FLAG Programs

  10. Alternative 1 (cont.) • If Cumulative Impact (CI) < 10% of Natural Conditions (NC) for Avg. of 20% Most Impaired Days then Area of State/Reservation Significant is > 5% of NC • If CI > 10% of NC Significant is 1% of NC (Exclude any Signif. Area if in lowest 20% of CI)

  11. Alternative 2 • Individual Area of State/Reservation Approach (Cumulative Impact not considered) • Based on Impact being Perceptible • Perceptible in range of 0.5 DV to 2.0 DV • Significant threshold 1 Deciview

  12. Alternative 3 • Individual Area of State/Reservation Approach (Cumulative Impact not considered) • Based on Rule Definition of Significant as “Contributor” to Visibility Impairment not a Sole or Perceptible “Cause” of Impairment • Significant Threshold 1% of Natural Background (about 10% of a Deciview)

  13. “Areas of State” for Mobile Source Impact Analysis • Counties Encompassing Urban Areas in 9-State Transport Regions with Populations greater than 250,000 • 11 Areas • 2 in AZ, 3 in CO, 1 in ID, 1 in NM, 2 in OR, and 2 in UT • California and Nevada analyzed separately since electing not to go 309

  14. Mobile Source Significance Trigger • Significant in Base Year (2003) and Future Year (2018) then Budget/Tracking Applies • Significant in Base but not Future Year and any pollutant reaches minimum before 2018 then Budget/Tracking Applies (SO2) • Significant in Base but not Future Year and all pollutants continually decrease then Future SIP revision, if needed, to meet Reasonable Progress Provision of Rule

  15. Road Dust Significance Trigger • If Road Dust Significant in Base and Future Year than Further Analysis after Expected Improvements to Estimated Dust Emissions/Modeling by EPA/WRAP • If still Significant than Reasonable and Appropriate Control Measures apply through SIP/TIP revision no later than 12/31/08

  16. Prelim. Modeling Results - On Road Mobile • Smallest Cumulative Impact in 2018: 0.28 DV at Mesa Verde NP • Largest Cumulative in 2018 : 0.78 DV at Zion NP • 2018 Nonroad Emission Inventory of Major Visibility Precursors is 2 X of On Road EI

  17. Preliminary Modeling Results - Road Dust • Smallest Cumulative Impact in 2018 0.08 DV at Weminuche Wilderness • Largest Cumulative Impact in 2018 0.31 DV at Black Canyon of Gunnison NP

  18. Conclusions • Need Complete Modeling Results (Nonroad + Areas) for Accurate Determination • Cumulative Mobile likely > 1.0DV • Unclear if any 309 area > 0.1 DV • State Road Dust may be < 0.1 DV • Concern that Future Nonroad Emissions Exceed On Road

  19. Mobile Source Emission Trend- Tons/Day NOx, SOx,, PM

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