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Varra Coal Ash Project <br /> Selenium Calculation <br /> This spread sheet calculates the steady state concentration at a point of compliance <br /> well located at a distance (x) down-gradient of the source area. The calculations and <br /> methods are describe in ASTM-38 RBCA. <br /> Spread Sheet Calculations Enter <br /> Enter Porosity (sand 0.3, silt 0.35, clay 0.4) 0.27 <br /> Enter hydraulic gradient[fUft] 0.0023 <br /> Enter hydraulic conductivity [cm/s] 0.044 <br /> Enter first-order degradation constant 0 <br /> Enter distance (x) to point of compliance[it] 200 <br /> Enter source width (perpendicular to flow in the horizonal plane) [it] 100 <br /> Enter source width (perpendicular to flow in the vertical plane(it] 7 <br /> Enter source area concentration (mg/L) 0.015 <br /> %= longitudinal dispersivity, [cm]= 0.10x= 610 cm <br /> ay= transverse dispersivity,[cm]=a,/3 203.3333 cm <br /> a,=vertical dispersivity, [cm]= u.)20 30.5 cm <br /> Ground water velocity [cm/s] = 0.000375 cm/s <br /> Ist error function 0.684429 <br /> 2nd error fuction 0.123703 <br /> erf(rl)=error function of evaluated for 1 st function = 0.670254 <br /> erf(Tl)=error function of evaluated for 2nd function = 0.138909 <br /> Steady State Concentration C(x) at Point of Compliance= r 1.40 gg/L <br /> C(x) = Coexp{ x rt f+4la. 11rerfl 4a x1 e( fl S��JI <br /> 12ax u 14 a.x 4 a�x <br /> r_4nz l <br /> erf(t)) = 1 - exp J l � <br /> C(x) = dissoTv-ed phase concentration along centerline (x, y= 0, z=0) of dissolved plume[g/cm'-H2O] <br /> C source = dissolved phase concentration in dissolved plume source area [g/cm'-H2O] <br /> x= distance along center line from down-gradient edge of dissolved plume source (cm) <br /> a,= longitudinal dispersivity,[cm] = 0.10x <br /> ) = first order degradation constant[d 1] <br /> u= Ki\� ground water velocity[cm/d] <br /> S„=source width (perpendicular to flow in the horizonal plane [cm] <br /> Sd= source width (perpendicular to flow in the vertical plane) [cm] <br /> ay= transverse dispersivity[cm]= a,/3 <br /> a,= vertical dispersivity[cm] = a,/20 <br /> erf(r))=error function of evaluated for value n <br /> Revised on March 18,1997 <br /> Page 1 <br />