1. Paved and Unpaved Road Dust
Bob Lebens,WESTAR Council
Fall Technical Conference
September 17, 2002

2. Monitoring Data
Fine soil and coarse particles are 6-26% of the annual average light extinction
Fine soil can account for 10-30% of the fine particulate mass
Fine soil is almost always <10%, but can be as high as 40% for the haziest days
Coarse material is usually <20%, but can be as high as 90%

3. GCVTC
Discounted future emissions from paved and unpaved roads – due to inventory and modeling weaknesses
Road Dust impacts presumed to be local
Recommended voluntary measures to control dust near Class I areas

4. Requirement
State determines, based on an assessment of the contribution of dust emissions from paved and unpaved roads on visibility conditions in Class I areas, that the contribution is either:
Insignificant, or
Significant

5. If Significant
State determines the “appropriate and necessary” emission management strategies for the Class I areas.

6. Appendices
Modeling assessment from the Regional Modeling Center. Assessment of the impact of dust emissions from paved and unpaved roads on the visibility in Class I areas.

7. Appendices – If Significant
Analysis of ‘necessary’ and ‘appropriate’ emission management strategies options and choices.
Basis of judgment for establishing ‘significance’ levels.

8. Preliminary Modeling Results
Smallest Cumulative Impact in 2018
0.08 deciview in Weminuche Wilderness
Largest Cumulative Impact in 2018
0.31 deciview at Black Canyon of Gunnison NP
(Note “Area of State” not defined – assumed to be state/reservation wide. Wind blown “natural” dust was not included in modeling and is difficult to characterize.)

9. Next Steps
Expert Panel review of dust emissions adjustments used in Modeling
Review complete by November
New WRAP Dust Emissions Joint Forum
Dust ‘Significance’ criteria may be the same as that selected for tailpipe emissions

10. Next Steps (continued)
WRAP/EPA technical refinements may delay ‘necessary and appropriate’ strategies (if dust is significant) until 2008.