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Section 1 <br />Introduction <br />1.2 Background Information <br />The following section provides background information on the use of attenuation <br />data for various metals of interest at the Sunday Mines Group. <br />1.2.1 Attenuation in Fate and Transport Assessment <br />The geochemical sorption potential (e.g., attenuation factor) is used in estimating the <br />retardation factor in groundwater. The retardation factor (R) is a measure of the <br />velocity of the constituent (e.g., arsenic, antimony, vanadium, etc.) within the <br />groundwater compared to the velocity of the groundwater itself and is given by the <br />following: <br />R = vg„/vc (1) <br />Where: <br />vgw = The velocity of the groundwater (ft/ day) <br />vc = The velocity of the constituent (ft/day) <br />The constituent generally travels more slowly than the groundwater due to <br />partitioning from the solution onto the aquifer matrix (R is always equal to or greater <br />than 1). An R value of 1 would indicate that no retardation is occurring and that the <br />velocity of the constituent is the same as the groundwater. The retardation factor is <br />• estimated based on partitioning theory as follows: <br />R =1 + Kd(0/ne) <br />Where: <br />(2) <br />R = retardation factor (unitless: velocity/ velocity) <br />Kd = partition coefficient or distribution coefficient <br />= bulk density (grams per cubic centimeter [g/cm3]) =1.6 <br />g/cm3 is typical standard value for soils <br />ne = effective porosity (unitless: volume/volume) = 0.3 is <br />typical standard value for soils <br />The geochemical sorption potential is expressed in terms of a value called the <br />distribution coefficient (Kd), which can be expressed as follows: <br />Kd (L / kg) = Concentration of constituent adsorbed to the solid (mg/kg) <br />Concentration of constituent in solution (mg/L) <br />This higher the geochemical sorption potential value, the more the constituent is <br />likely to partition to the solid matrix (e.g., absorb to the soil) as it moves with <br />groundwater. <br /> <br />Cm 1-2 <br />TA64966•Denison Mineffask Order 3 - DMO Sampling and Analysis Plan\Task 3.12 - Soil, Ore, Rock Data Assessment RepodlSunday Rods ReporNWacnmentsWtenuation Reporl_"rking draft 040309.doc