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and placed on the stockpile, which is not an everyday occurrence.For example, in 2007 only <br />approximately 25 water trucks were spread on all of the soil stockpiles. At a rate of 25 water <br />trucks per year it would take approximately 78 years to apply adequate water and salts to the soil <br />stockpiles to create the increase in soil salinity that was observed at the New Horizon Mine. <br />Weathering. <br />Physical and chemical weathering of the soil minerals is the other likelycause of the increased <br />soil salinity observed between native soil and the soil stockpiles at the New Horizon Mine. <br />Physical and chemical weathering is a process where the soil minerals and rocks are exposed to <br />air water and organisms. Under natural in-situ conditions soil physical and chemical weathering <br />is a relatively slow processdue to the fact that most primary and secondary minerals are <br />sparinglysoluble (Robarge, 1998).However, these conditions assume that the bulk stage of the <br />minerals have relatively low solid phase(i.e.low specific surface area)in contact with the <br />aqueous phase of the system (Robarge, 1998). When the soil is excavated anddisturbed,such as <br />occurs during the mining process,physical and chemical weathering processes can be <br />accelerated. Under disturbed conditions the primary and secondary minerals’specific surface <br />area is greatly increased thus increasing the contact between the solid and aqueous phase in the <br />soil.Acceleration ofthe physical and chemical weathering process is due to the increase in <br />specific area of the minerals that occurs during the excavation process.This increase in physical <br />and chemical weathering is analogous to the time difference that it takes ground sugar compared <br />to a sugar cube to dissolve (weather) in a glass of tea. <br />Dissolution of ions from the solid surfacesandphysical and chemical weatheringareincreased <br />as the soil surface area is increased (Robarge, 1998). However unlike physical and chemical <br />weathering, dissolution can be affected by pH, organic matter, and solution composition. The <br />process of stockpiling soils is known to decrease soil organic matter as it decomposes as the <br />system becomes highly oxygenated during excavation and movement. As the organic matter <br />present in the soil decomposes,metals ions are released into the aqueous phase (Robarge, 1998), <br />increasing soil salinity. <br />Physical and chemical weathering and dissolution in the soil stockpiles is a likely cause of the <br />increased soil salinity observed. The increase in soil salinity is expected and is natural as soil is <br />removed from native conditions and exposed to a new environment. As the soil is exposed to the <br />new environment the system will develop a new equilibrium at which point the physical and <br />chemical weathering and dissolution processes will begin to stabilize and no further increase in <br />soil salinity will be observed. <br />Additional information supports the conclusion that the use of mine pit water for dust control on <br />stockpiles is an unlikely cause of increased salinity. A review of this soil stockpile salinity data <br />reveals remarkable uniformity (i.e. low statistical variability).Thishigh degree of uniformity is <br />especially true in the largest soil stockpile, Lift B. In Lift Bthe average soil ECewas 3.7 dS/m <br />with a minimum ECeof 2.5 dS/m andmaximum ECeof 5.3 dS/m. The standard deviation of the <br />Lift B soilwas 0.5dS/m(Table 1).The standard deviation was calculated based on a total <br />sample number of 90, which is a large sample set to evaluate. <br />7 <br />{00136879.1 } <br />