2012-10-01_REVISION - M1977305 (16)

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range of 6.5 to 9.0 while the EPP sample at LP -21 has a pH of 9.4. In general, the more sensitive an organism is to a low pH, the stronger the toxic response to Al concentrations to falling pH levels (Baker and Schofield, 1982). Based on the site distance to the nearest water body, it is highly unlikely, even under the most extreme conditions, that aluminum could be transported such a large distance and impact aquatic life in the San Miguel River. Aluminum is a major component of clays and shales that comprise a significant portion of the site geology. Consequently, the detection of aluminum in the SPLP analysis is not surprising. 14.2 Mobility of Detected Uranium Ore Related Constituents Two factors control the mobility of constituents identified in the SPLP analysis - precipitation and sorption. Limited precipitation in the area combined with high evapotranspiration rates makes it unlikely that sufficient precipitation is available to mobilize ore related constituents any significant distances. The most likely scenario is that any precipitation that falls in the area would be contained in the topsoil and used by plants covering the waste rock stockpiles once future mining and remediation is completed. The simplest and most common method of estimating contaminant retardation is based on the partition (or distribution) coefficient, K The Kd parameter is a factor related to the partitioning of a contaminant between the solid and aqueous phases. It is an empirical unit of measurement that attempts to account for various chemical and physical retardation mechanisms that are influenced by a myriad of variables. The Kd metric is the most common measure used in transport codes to describe the extent to which contaminants are sorbed to soils. A primary advantage of the K model is that it is easily inserted into hydrologic transport codes to quantify reduction in the rate of transport of the contaminant relative to groundwater, either by advection or diffusion. The partition coefficient, K is defined as the ratio of the quantity of the adsorbate adsorbed per mass of solid to the amount of the adsorbate remaining in solution at equilibrium. For the reaction the mass action expression for K is A +C; =A; Kd = Mass of Adsorbate Sorbed (A ) Mass of Adsorbate in Solution (C; ) Where A = free or unoccupied surface adsorption sites, C, = total dissolved adsorbate remaining in solution at equilibrium, and A; = amount of adsorbate on the solid at equilibrium. O'Connor Design Group Inc. U - 20