treasure valley road dust study: final report - ResearchGate

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4.3.2 Meteorological Effects on Unpaved Road Emissions The TRAKER loop included a 1 km section of private unpaved road (Howry) that was traversed each time the loop was executed. The emissions potential for each day the loop was executed was averaged over the entire length of the unpaved road. The result appears as a time series in Figure 4-8. The black circles correspond to the emissions potential in [g/vkt/mps]. The black squares correspond to daily precipitation in mm. The gray line is a time trace of the relative humidity. Emissions potentials fall into three distinct categories outlined by the gray boxes: “dry conditions”, “day after rain”, and “wet conditions”. The emissions potentials and daily precipitation share the same y-axis scale on the left, while the relative humidity uses the right y-axis scale. During and immediately after a rain event while the relative humidity is still high (3/3/01), emissions potentials are very low and correspond to “wet conditions”. 24 hours after a rain event (“day after rain”), when the relative humidity has had a chance to sub side and the top layers of soil are drying, emissions potentials are higher than under “wet conditions”. 48 hours or more after a rain event, emissions potentials are even higher (“dry conditions”). If we consider the “dry conditions” as a baseline value, then under wet conditions, emissions are on average 7.9% of the baseline value and under “day after rain”, emissions are 35% of their baseline values. This trend seems to hold regardless of the amount of rainfall, though we note that the range of daily rainfall amounts that were reported for the 2/23/01 to 3/20/01 period was modest (0.25 mm - 0.77 mm or 0.01 in – 0.03 in). AP-42 (USEPA, 1999) suggests the approximation that emissions from unpaved roads should be set to zero for all days where the total daily rainfall exceeds 0.25 mm. The results of the TRAKER loop indicate that in addition to reducing emissions for days when rainfall is reported, unpaved road emissions should also be reduced for the 24-hour period that follows the day that rainfall was reported. Physically, results from the TRAKER loop suggest that a thin layer of soil at the surface dries quickly, but that the soil underneath may remain wet for at least 48 hours, considerably reducing the potential for dust emissions. Emissions Potential [g/vkt/mps] Or rainfall in mm 10.00 Dry Conditions Day After Rain 1.00 Wet conditions 0.10 TRAKER Rainfall "RH" 2/23/01 2/28/01 3/5/01 3/10/01 3/15/01 3/20/01 Date 100 90 80 70 60 50 40 30 20 10 0 Figure 4-8. Plot of emissions potential of unpaved road on TRAKER loop, daily precipitation, and relative humidity. Emissions potentials and rainfall use the left y-axis; relative humidity uses the right y-axis. 4-20
4.4 Special Studies During the TVRDS, experiments were carried out to determine the impact of street sweeping on paved road dust emissions. These experiments were planned and executed in coordination with Kevin Barton of the Ada County Highway District Road Maintenance (ACHD). 4.4.1 Winter Sanding Experiment The winter sanding experiment was originally designed to collect TRAKER data from a common set of roads prior to a snowstorm event, after a snowstorm and sand application, and after the sand had been removed from the roads by street sweeping. Since, no snow events occurred in the Treasure Valley during the field study a controlled experiment was designed to measure the effects of sanding and sweeping on PM emissions. 4.4.1.1 Testing Protocol The winter sanding experiment took place on the morning of 03/15/2001. The first test was carried out in Boise on the rightmost eastbound land on Chinden Road between 50 th and 42 nd St. In this area, Chinden is a principle arterial with commercial zoning on both sides of the street. The road has four traffic lanes and a turn lane in the middle. The shoulder of the road is paved and 1 meter deep in areas where there are no ingress-egress points. Traffic counts were obtained by COMPASS on 09/24/97 and reported to be 14,192 vehicles per day in one direction. The COMPASS traffic demand and forecasting model calculated year 2001 average daily traffic (ADT) of 23,392 in both directions or approximately 6,000 ADT per lane. The posted speed limit on this road is 45 mph. The second test was performed on the westbound lane on Rose Hill/Franklin Road between Owyhee and Orchard. Rose Hill Road turns into Franklin Road west of Roosevelt. This road section has 2 traffic lanes and a turn lane. The road is in a residential neighborhood with curbing on both sides. Between 03/16/2001 4:00 (Friday) and 03/18/2001 5:00 (Sunday), DRI deployed traffic counters on the westbound section of Rose Hill 200 ft west of Owyhee. Total one-way counts were measured at 5,700 on Friday and 4,200 on Saturday with a median speed of 33.1 mph. Modeled 2001 ADT for the road was 17,910 in both directions or approximately 9,000 ADT per lane. The posted speed limit on Rose Hill/Franklin is 35 mph. Chinden and Rose Hill/Franklin were each divided into three test sections as shownin Figure 4-9, Figure 4-10, and Table 4-10. Table 4-10. Description of Test Section for Sweeping-Sanding Tests Test Section Activity Chinden Rose Hill/Franklin Section 1 Sanded and Eastbound b/w 50 th St. and swept with Bradley (480 meters) vacuum sweeper Section 2 Sanded and Eastbound b/w Bradley and swept with 45 th St. (660 meters) mechanical sweeper Section 3 Sanded but Eastbound b/w 45 th St and not swept 42 nd St (600 meters) Westbound b/w Owyhee and Latah (390 meters) Westbound b/w Latah and Roosevelt (420 meters) Westbound b/w Roosevelt and Orchard (890 meters) 4-21
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TREASURE VALLEY ROAD DUST STUDY: FI
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EXECUTIVE SUMMARY The Idaho Departm
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TABLE OF CONTENTS 1. INTRODUCTION..
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6.3 DISCUSSION ....................
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are strongly correlated and that on
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Figure 4-17. Map of street sweeper
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xvi
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Table 5-3. Speeds and VKT by county
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Table A-28. Laboratory Silt Analysi
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?? To assess the impact of winterti
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2. SILT MEASUREMENTS For this study
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vehicle tires. The lengths of the s
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Page 31 and 32: Table 2-5 Silt Content and Silt Loa
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Page 62 and 63: 4.1.1 Converting TRAKER Data Into E
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Page 68 and 69: a. b. Figure 4-1. Map of TRAKER Str
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Page 101 and 102: Table 5-9 Precipitation and snow co
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Table 7-6. Source profiles of Winte
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Bliss experiments were significant
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section was swept with a vacuum swe
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8.3 Differences Between Emissions M
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determine at this time what fractio
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sweepers to reduce PM 10 emissions
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McMahon T.A., and P.J. Denison (197
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Figure A-1. Map of Sample Collectio
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Table A-2. Summer 2001 Silt Samplin
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Table A-3. Laboratory Silt Analysis
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Figure A-3. Map of Silt Loading Loc
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Figure A-11. Sampling locations of
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APPENDIX B. BOISE PRECIPITATION AND
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Pecentile among days with precipita
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A.1 Wind speed The cumulative frequ
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APPENDIX C : EMISSIONS INVENTORIES:
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C.1.1.2a Field List for worksheets
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values specified by AP-42 and do no
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