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Section 1 <br />Introduction <br />On behalf of the Denison Mines (USA) Corp (Deison), CDM Inc. (CDM) completed an <br />attenuation study of the rock and soil material underlying the development rock piles <br />at the Sunday Mines Group. The Sunday Mines Group is located in San Miguel <br />County, Colorado and includes: <br />¦ The Sunday Mine; <br />¦ The Carnation Mine; <br />¦ The West Sunday Mine; <br />¦ The St. Jude Mine; and <br />¦ The Topaz Mine. <br />The mines produce uranium and vanadium ore from mineral deposits of the Uravan <br />District, one of the major uranium-producing mineral districts in the United States. As <br />discussed in the data collection work plan for the Sunday Mines Group (CDM 2008), <br />several development rock and soil samples were collected to support this attenuation <br />study. <br />1.1 Attenuation Study Objectives 0 <br />Natural attenuation processes include adsorption, dilution, advection, dispersion, and <br />other processes. These processes are important to consider in the evaluation of the <br />potential for constituents within percolation from development rock piles to migrate <br />through soil or shale underlying or adjacent to the piles and into underlying <br />groundwater. <br />Within the vadose zone, adsorption is one of the most dominant processes controlling <br />natural attenuation. Adsorption is a process where dissolved metals or metalloids <br />attach to the surface of solid particles and are removed from the dissolved phase, <br />therefore reducing the aqueous concentration. Adsorption can be an important <br />attenuation mechanism to reduce the potential for constituents mobilized from <br />development rock to affect either surface water or groundwater resources. The <br />objective of this attenuation study is to evaluation of the geochemical adsorption <br />potential of soils underlying the development rock piles.. Specifically, the objectives of <br />the chemical attenuation tests on the Sunday Mine Group soils are as follows: <br />¦ Determination of the soil partition coefficients for constituents that exceeded <br />screening levels based on the MWMP test <br />¦ Calculation of the soil retardation factors for constituents that exceeded screening <br />levels based on the MWMP test <br />i <br />1-1 <br />T:%649884)em3w Min--ask Order 3 - DMO Sampling and Analysis Plan%Task 3.12 - Soil, Ore, Rock Data Assessment RepodlSunday Rock Repor0A0achments0thmuation ReporLmrking draft 040309.dw