Emission Factor
Calculation for Unpaved Road
To
estimate the emission factor for the construction dust emission due to the
vehicles moving on the unpaved haul roads.
1.
Emission
Factor (lb/VKT)
= k(s/12)a
(W/3)b x
S
(Mdry
/0.2)c 15
(As given in
Compilation of Air Pollutant Emission Factors, AP-42 (Section 13.2.2), 5th
Edition, published by USEPA)
VKT – vehicle kilometers traveled
2.
Conversion
of Emission Factor: E(g/VKT) = E(lb/VMT) / 281.9
3.
Emission
rate (g/m2/s) = Emission Factor x Distance traveled per hour /
unpaved area
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Variables |
Value |
Source |
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Mean
Vehicle speed(S) |
3.1 mph |
Assume |
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Silt
Content (s) |
8.5% |
Typical
value given in AP-42 |
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Mean
vehicle weight (W) |
33 Mg |
Assume |
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Material
moisture content (Mdry) |
0.2% |
Typical
value given in AP-42 |
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Distance
traveled per hour |
0.808km/hr |
Distance
traveled per trip around the site is 0.404km, assuming 2 trips per hour. (2 x
0.404 = 0.808 km/hour) |
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Unpaved
area |
2688 m2 |
Assumed
7m wide haul road along the site boundary |
Emission
Factor Calculation for Bulk Materials Handling
To estimate the emission factor for the construction dust emission due to bulk materials handling during the excavation work.
1.
Emission
Factor(kg/Mg) = k (0.0016) x (U/2.2)^1.3 / (M/2)^1.4
(As given in
Compilation of Air Pollutant Emission Factors, AP-42 (Section 13.2.4), 5th
Edition, published by USEPA)
2. Amount of material to be removed per hour, R (kg/hr)
= Volume of soil x Density / Duration of excavation
3.
Emission
Rate(g/m2/s) = Emission
Factor x R / Excavation Area
It is assumed that the excavation area to be the
whole construction site area of the WFM.
|
Variables |
Value |
Source |
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Particle
size multiplier(k)
|
0.74(TSP) 0.35(RSP) |
As
given in AP-42 |
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Mean
wind speed (U) |
2.41 m/s |
Calculated
from the meteorological data for Year 1999 provided by HK Observatory |
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Material
moisture content(M) |
4.8% |
Assumed
within the range of source condition in developing equation 1 in AP-42 |
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Volume
of soil to be excavated |
5,000m3 |
As
estimated by ASD |
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Soil
Density |
2,000kg/m3 |
Typical
value for soil |
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Duration
of excavation |
112 hours |
Given
the typical excavation rate is 367.2m2/day, 14 days is required to
complete the excavation of 5,000m3 soil. (14d x 8hrs/d) = 112 hrs) |
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Excavation
Area |
8760m2 |
Whole
site area |
Emission
Factor for Stockpile Wind Erosion
The emission factor for the
construction dust emission due to stockpile wind erosion is given in Compilation of Air Pollutant Emission
Factors, AP-42 (Section 11.9.2), 5th Edition, published by USEPA
as 0.85 Mg/hectare/yr (= 2.695 x 10-6) for TSP.
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CALCULATION
OF EMISSION FACTORS |
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According to U.S. EPA, Compilation of Air Pollutant Emission Factors,
AP-42 |
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Unpaved
Road |
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For
concrete lorry mixer & dump truck (36ton) |
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mean vehicle speed(S), mph |
surface material silt content (s),
% |
mean vehicle weight (W), tons |
material moisture content (Mdry),% |
PM10 Emission factor
(E), lb/VMT |
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RSP |
3.1 |
8.5 |
33 |
0.2 |
1.067 |
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TSP |
3.1 |
8.5 |
33 |
0.2 |
5.214 |
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Constants
for Equation 1 |
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k (lb/VMT) |
a |
b |
c |
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RSP |
2.6 |
0.8 |
0.4 |
0.3 |
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TSP |
10 |
0.8 |
0.5 |
0.4 |
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**
Equation 1 : E = |
k (s/12)^a x (W/3)^b |
x (S/15) |
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(Mdry / 0.2)^c |
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( In
case of a mean vehicle speed (S) less than 15mph, Equation 1 is recommended
to be muliplied by (S/15)) |
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Conversion
of Emission Factor from lb/VMT to g/VKT : |
1 lb/VMT =
281.9 g/VKT |
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RSP |
3.01E+02 |
g/VKT |
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TSP |
1.47E+03 |
g/VKT |
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Assume unpaved area(m2)
= |
2688 |
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Distance travelled per hour = |
0.808 |
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Emission
rate, g/m2/s: |
Emission
Factor X distance travelled per hour / unpaved area |
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Unmitigated |
Mitigated 1 |
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RSP |
2.51E-05 |
1.26E-05 |
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TSP |
1.23E-04 |
6.14E-05 |
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1 With 50% reduction of unmitigated
emission rate |
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Bulk
Materials Handling |
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particle size multiplier (k) |
mean wind speed (U), m/s |
material moisture content (M),% |
Emission factor (E), kg/Mg |
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TSP |
0.74 |
2.41 |
4.8 |
3.91E-04 |
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RSP |
0.35 |
2.41 |
4.8 |
1.85E-04 |
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**
Equation 2 : E = k (0.0016) x (U/2.2)^1.3 / (M/2)^1.4 |
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For
Excavaion |
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Volume of
soil to be excavated, m3 : |
5,000 |
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Soil Density,
kg/m3 : |
2,000 |
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Duration
of excavation (14days) |
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(assume
26 working days per month and 8 hours a day) |
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= 14 x 8 =
112 hr |
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Amount of
material to be removed per hour (R), kg/hr |
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= Volume
of soil X Density / number of operation hour = |
89285.71 |
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Emission
Rate, g/s/m2 |
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Unmitigated |
Mitigated 1 |
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TSP |
1.11E-06 |
5.53E-07 |
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RSP |
5.23E-07 |
2.62E-07 |
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1 With 50% reduction of unmitigated
emission rate |
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**
Equation : Emission Rate = E x R / Area |
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(assume
loading / unloading area = whole area of 8760m2) |
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Stockpile
Wind Erosion |
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Emission rate, Mg/hectare/year |
Emission rate, g/s/m2 |
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Unmitigated |
Mitigated 1 |
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TSP |
0.85 |
2.695E-06 |
1.35E-06 |
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RSP |
*Assume half of TSP=RSP |
1.348E-06 |
6.74E-07 |
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1 With 50% reduction of unmitigated
emission rate |
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