# Appendix 4.1 Emission Factors for Construction Dust Emission

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

 Variables Value Source Mean Vehicle speed(S) 3.1 mph Assume Silt Content (s) 8.5% Typical value given in AP-42 Mean vehicle weight (W) 33 Mg Assume Material moisture content (Mdry) 0.2% Typical value given in AP-42 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) 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 Particle size multiplier(k) 0.74(TSP) 0.35(RSP) As given in AP-42 Mean wind speed (U) 2.41 m/s Calculated from the meteorological data for Year 1999 provided by HK Observatory Material moisture content(M) 4.8% Assumed within the range of source condition in developing equation 1 in AP-42 Volume of soil to be excavated 5,000m3 As estimated by ASD Soil Density 2,000kg/m3 Typical value for soil 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) 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.

 CALCULATION OF EMISSION FACTORS - According to U.S. EPA, Compilation of Air Pollutant Emission Factors, AP-42 Unpaved Road For concrete lorry mixer & dump truck (36ton) 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 RSP 3.1 8.5 33 0.2 1.067 TSP 3.1 8.5 33 0.2 5.214 Constants for Equation 1 k (lb/VMT) a b c RSP 2.6 0.8 0.4 0.3 TSP 10 0.8 0.5 0.4 ** Equation 1 :  E = k (s/12)^a x (W/3)^b x (S/15) (Mdry / 0.2)^c ( In case of a mean vehicle speed (S) less than 15mph, Equation 1 is recommended to be muliplied by (S/15)) Conversion of Emission Factor from lb/VMT to g/VKT : 1 lb/VMT = 281.9 g/VKT RSP 3.01E+02 g/VKT TSP 1.47E+03 g/VKT Assume unpaved area(m2) = 2688 Distance travelled per hour = 0.808 Emission rate, g/m2/s: Emission Factor X distance travelled per hour / unpaved area Unmitigated Mitigated 1 RSP 2.51E-05 1.26E-05 TSP 1.23E-04 6.14E-05 1 With 50% reduction of unmitigated emission rate Bulk Materials Handling particle size multiplier (k) mean wind speed (U), m/s material moisture content (M),% Emission factor (E), kg/Mg TSP 0.74 2.41 4.8 3.91E-04 RSP 0.35 2.41 4.8 1.85E-04 ** Equation 2 : E = k (0.0016) x (U/2.2)^1.3 / (M/2)^1.4 For Excavaion Volume of soil to be excavated, m3 : 5,000 Soil Density, kg/m3 : 2,000 Duration of excavation (14days) (assume 26 working days per month and 8 hours a day) = 14 x 8 = 112 hr Amount of material to be removed per hour (R), kg/hr = Volume of soil X Density / number of operation hour = 89285.71 Emission Rate, g/s/m2 Unmitigated Mitigated 1 TSP 1.11E-06 5.53E-07 RSP 5.23E-07 2.62E-07 1 With 50% reduction of unmitigated emission rate ** Equation : Emission Rate = E x R / Area (assume loading / unloading area = whole area of 8760m2) Stockpile Wind Erosion Emission rate, Mg/hectare/year Emission rate, g/s/m2 Unmitigated Mitigated 1 TSP 0.85 2.695E-06 1.35E-06 RSP *Assume half of TSP=RSP 1.348E-06 6.74E-07 1 With 50% reduction of unmitigated emission rate