treasure valley road dust study: final report - ResearchGate

For the winter samples, silt loading on paved roads ranged from 0.7 g/m 2 at the Riva
Ridge site to 6.6 g/m 2 at Amity Road. Silt loadings by roadway classification for both Ada and
Canyon Counties averaged 1.9, 2.9, and 4.0 g/m 2 for arterial, collector, and local roads
respectively. This is consistent with the expectation that roads with higher Vehicle Kilometers
Traveled (VKT) and travel speeds are likely to have lower loadings than less frequently-used
roads.
Silt loadings in the summer were substantially lower than winter. Summer values ranged
from 0.2 g/m 2 (West Park Dr.) to 1.0 g/m 2 (Riva Ridge). Note that the silt loading on 6th St was
5.0 g/m 2 . However, that sample was collected when the street was covered with gravel chips as
part of the summer chip-sealing program; this sample can be used to estimate road dust
emissions under chip-sealing conditions, but should not be included in calculating seasonal or
countywide averages. Summer silt loadings by roadway classification were 0.5, 0.7, and 0.4
g/m 2 for arterial, collector, and local roads, respectively. These values are approximately four to
ten times lower than winter silt loadings. Figure 2-2 shows comparisons between winter and
summer 2001 silt loadings by site. Of the nine sites, only Garrity Blvd, an arterial, and Riva
Ridge, a local road, had comparable values between summer and winter. 6th St silt loadings
were also similar between the two seasons, though, the summer 6th St sample is not
representative due to the influence from chip-sealing activities.
Figure 2-2. Comparison of Winter and Summer 2001 Silt Loadings. Summer 2001 6th St sample influenced
by chip-sealing operations.
Silt Loading g/m 2
8
7
6
5
4
3
2
1
0
Winter 2001
Summer 2001
Front St.
Maple
Grove
Garrity Blvd
Riva Ridge
13th St
Amity Rd
Apple St.
West Park
Dr
6th St.
Site
Silt loadings from the present study are compared to the values used to prepare the 1995
emissions inventory (SAI, 1997) in Table 2-7. Silt loading values used in the 1995 emissions
inventory were based on average and wintertime default values specified by AP-42 (USEPA,
1995). Compared to the default wintertime values used to compile the 1995 emissions inventory,
silt loadings measured in winter 2001 were higher for arterial and local roads and comparable for
2-8