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1 <br /> Geologcco'Techntcslru Page 3 <br /> Monta <br /> Risk Evaluation Work Plan <br /> Project No 724 2 <br /> March I8,2002 <br /> ' The mass of contaminant in each cylinder is determined b the following calculation <br /> Y Y g <br /> r ❑ Squaring the radius of the cylinder and multiplying by Pi (7r) to determine the area <br /> o The area is then multiplied by the thickness of the layer to get the volume <br /> ❑ The volume is multiplied by the density of the soil (lbs/ft') and then by 0 4536 to <br /> convert from pounds of soil to kilograms of soil - <br /> ' ❑ The contaminant load is then multiplied by this number to give the mass in milligrams <br /> ❑ The contaminant mass in milligrams is then converted to kilograms <br /> The groundwater value is calculated much the same except that the groundwater <br /> contaminant load is multiplied by the volume of groundwater in the pore space of the soil <br /> The volume of groundwater is determined by multiplying the porosity of the soil times the <br /> ' volume of soil in the saturated zone <br /> After the above tasks are completed the groundwater gradient trends can be re-evaluated for <br /> assessing the risk the gasoline plume poses to sensitive receptors (1 e , water wells & rivers) <br /> ' 2.2 Contaminant Fate & Transport Calculations <br /> Fate and transport calculations will be performed to determine possible travel times of <br /> contaminants to nearby receptors Geophysical testing has not been performed on samples <br /> from the site so site specific data are not available regarding porosity, conductivity, organic <br /> carbon, etc , therefore text book values will be used that closely match the soil types of the <br /> M site <br /> In the determination of groundwater velocities for the site, the following equation for <br /> r seepage velocity will be used <br /> V = (K/n) x (Ah/Al) <br /> ' • Where V equals average groundwater seepage velocity <br /> • K equals the hydraulic conductivity <br /> r • n equals effective porosity <br /> • (Ah/el) equals the groundwater gradient <br />' <br /> Specific contaminant migration velocity cannot be determined due to the lack of site <br /> specific data, particularly organic carbon content, however there are values available in the <br /> literature that can be used to help determine contaminant flow <br /> 1 <br /> 1 <br /> r <br /> r <br />