Prefeasibility Access Road Design-Revised
29
Water Suppression
This analysis provides an estimate of the water required for dust suppression on
the Miller Creek Route (application intensity) as determined by
Control of
Fugitive Dust Sources
, EPA-450/3-88-908 (1988). The amount of water necessary
for the reduction of 75% of dust is an annual weighted daily average of 64,376
gallons per day. This accounts for a higher evaporation rate during summer
months, and thus the need for more water application during summer months,
which is considered May through December for this evaluation. This calculation
is detailed below.
Equation 3-2 in EPA-450/3-88-908 provides an empirical estimate for control
efficiency of unpaved road emissions:
= 100 − 0.8 × × ×
Where:
C
= average control efficiency (%)
p
= potential average hourly daytime evaporation rate (mm/hr)
d
= average hourly daytime traffic rate (vehicles per hour)
t
= time between applications (hours)
i
= application intensity (L/m
2
)
Equation 3-2 can be rearranged to solve for
i/t
to determine the water
application rate that would result in a specified control efficiency for PM
10
. This
results in the following equation:
= 0.8 × × 100 −
Table 1, Miller Creek Route, Water Application Intensity for Dust Suppression
(attached) presents this calculation for the Miller Creek Route. For this analysis,
a control efficiency of 75% is used based on information in EPA-450/3-88-908
which indicates optimal dust control of 75% is achieved when the moisture
content of the surface material is twice that of its normal moisture content (See
EPA-450/3-88-908, Figure 3.3). Efficiency of water suppression decreases
beyond twice normal moisture content. Table 1 also presents the estimate of
water required for 50% and 90% control for a comparison of the effective use of
water resources.
Table 1, Miller Creek Route, demonstrates a required application rate of 0.0034
gal/ft2 per hour to achieve the targeted 75% control efficiency during non-
summer months, and 0.0045 gal/ft2 per hour during summer months. This
