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disturbance of the storage pile and is expressed in units of grams per square meter(g/mZ)per year. The following equations were used to calculate the emission factor. EF =kj',P,. P. =58(u* — u;)Z + 25(u* —u,);P. =0 for u' <_u, u' =0.053 uIa where: _ EF = emission factor(g/m2/yr) k = aerodynamic particle size multiplier(0.5)dimensionless P = erosion potential(g/m2) N = number of disturbances(366 disturbances per year) U. = friction velocity(m/s) U, = threshold friction velocity(1.02 m/s) uio = wind at reference height of 10 m(19 m/s) The basis of this methodology is that wind-blown dust from exposed areas will occur only when two conditions are met: the surface of the exposed area is disturbed and winds occur in excess of a threshold wind speed. Once the two conditions have been met,the emission factor is used to — determine bow much dust is generated. No more wind erosion occurs until the surface is again disturbed and the wind again exceeds the threshold speed. For conservatism,the calculation assumes the storage piles will be disturbed daily and, therefore,N equals 366 disturbances per year. Based on available data,the emission factor for wind erosion activities is 5.25 pounds of PM10 per square meter of stockpile(uncontrolled) and 1.31 pounds per square meter of stockpile (controlled). Emissions were based on a continuously exposed stockpile area of 50 square — meters. To account for emission controls, a control efficiency of 75%was applied. Unpaved Roads — When a vehicle travels over an unpaved road,the force of the wheels on the road surface causes pulverization of surface material. Particles are lifted and dropped from the rolling wheels,and the — road surface is exposed to strong air currents in turbulent shear with the surface. The turbulent wake behind the vehicle continues to act on the road surface after the vehicle has passed. The _ emission factors were calculated using the methodology found in Section 13.2 of AP-42, Unpaved Roads. The equation for developing the emission factor is: EF = k(S/12)a(W/3)°[(365-p)/365] (1-CE)