Challenges in On-Road Fugitive Dust Estimation: An MPO Perspective

1. Fugitive Dust Estimation Methods & On Road Mobile SourcesAn MPO’s Perspective

2. Utah Valley Metropolitan Planning Organization

4. Metropolitan Transportation Planning and Programming • The Mountainland Association of Governments (MAG) is the designated Metropolitan Planning Organization (MPO) for transportation planning in the Utah Valley Metropolitan Area Boundary. • The Transportation Equity Act for the 21st Century (TEA-21) and the Clean Air Act Amendments of 1990 require the MPO to develop a long-range regional transportation plan (LRP) and short-range transportation improvement program (TIP) that conform with the applicable State Implementation Plan (SIP) for air quality.

7. Transportation Conformity and Funding • Transportation conformity is an analytical process required of Metropolitan Planning Organizations (MPOs), pursuant to the Clean Air Act Amendments (CAA) of 1990. • TEA -21 links compliance with the conformity requirements to continued FHWA and FTA funding of transportation plans, programs, and projects.

8. Conformity Lapse • When the conformity analysis for the Long Range Plan shows non compliance with SIP MVEB budgets, all Capacity Increasing Projects (new projects) come to a screeching halt – and Federal Funding is at risk. • Utah County just emerged from a 32 Month conformity lapse – even though no exceedences were registered since 1992!!

9. Motor Vehicle Emission Budgets • MVEBs are excruciatingly hard to change. • Change requires a SIP revision. • Most on-road pollutants will have a technological solution to facilitate reduction or even elimination. • FUGITIVE DUST attributed to ON ROAD –has no remedy – according to current “thinking”.

12. On Road Fugitive Dust Estimation ? • Current EPA approved estimation methods – Part 5 model and AP-42. • EPA is currently evaluating comments on the proposal to declare AP-42 (5th edition) as the Approved Estimating Model. • 5th edition did nothing to improve or update on road dust estimation – it only separated Exhaust, Tire, and Brake-wear rates that can be estimated with Mobile 6.2 .

13. On Road Fugitive Dust Estimation ? • The Utah PM10 SIP, developed in 89–90 and approved in 92 assumed all silica on filters was On-Road related. • By Weight – road dust & salting/sanding “inventories” accounted to 49.1% of all direct PM10 from ALL sources. • Design day value was 254µg/m³.Road dust and salting/sanding contribution was 4.8µg/m³ (1.9%).

14. On Road Fugitive Dust Estimation ? • The recent SIP revision – adjusted (?) the inventories from 250.2 ton/month to 99.3 t/m a 61% reduction. • Modelers of the Dispersion Model based PM10 Maintenance Plan – had to discard 75% of the dust inventories in order to replicate Filter values –that corresponds to a 400% over estimation using current tools!

15. On Road Fugitive Dust Estimation ? • The modelers for the WRAP dispersion model encountered the same experience and had to reduce road dust inventories by 75%! • Neither the 5th edition, nor any other edition, deals with the flawed and uncertain linear assumption that more VMT means more dust.

16. On Road Fugitive Dust Estimation ? • To illustrate the flaws in the AP-42 road dust estimation method one can compare freeway silt loads to freeway dust estimates. Salt Lake County has 679 lane miles of freeways, each lane is 12 feet wide which results in a total pavement area of nearly 4 million square meters. With a silt load of 0.06 grams per square meter there is approximately 0.26 tons of silt on the freeways. But according to the PART5 model, when 8.3 million miles of vehicle travel occurs over that 1/4 ton of silt it turns into 5.0 tons of PM10 size dust!

17. On Road Fugitive Dust Estimation ? • The models assume a steady state relationship between silt, traffic, and dust when in fact they are in a dynamic relationship (Kitchen floor analogy).

18. On Road Fugitive Dust Estimation ? • Many of the sources of roadway silt are poorly understood and are the result of non-highway activities. Gravel operations, wind blown dust, litter, carry out, erosion, spills, and biological debris are due to events that should be controlled outside the roadways boundaries. • Only pavement wear and ice control compounds are related to roadways.

19. On Road Fugitive Dust Estimation ? • Dust models do not account for rapid precipitation of larger dust particles. • Source apportionment does not consider background dust and assumes ALL dust must be from traffic. • All road dust studies commissioned to date used road-side monitoring and could not reconcile model findings with the National Site Monitors filter data.

20. On Road Fugitive Dust Estimation ? • When added meteorological events – even the road side modeling could not be validated! • With such flawed and uncertain tools one should hesitate in accepting any current model as the “sanctioned methodology” for road dust estimation until better understanding of the subject is achieved. • Allowing states to define dust as an area source would retain dust as an important component in the regional attainment analysis without compromising critical transportation funding with dubious road dust models.

21. Dust Control ? • Suggested control measures for fugitive dust, particularly street sweepers, appear counter productive to winter inversion PM10 problems – but yield dramatic “benefits” according to EPA guidance.

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