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Defining “Significant Impact” from Mobile Sources and Road Dust

Explore the impact of mobile sources and road dust on visibility impairment in Colorado Plateau areas. Discuss emission restrictions and tracking measures for compliance. Evaluate alternatives and recommendations for defining significance.

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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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