2025-06-30_PERMIT FILE - C1981019 (6)

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RULE 2 PERMITS Soil samples were collected from each major horizon and sub -horizon at the sample sites. Approximately two quarts of soil material per sample were collected into clean Ziploc plastic bags. Sample material was field screened over a #10, 2 mm, soil screen to provide improved estimates of coarse fragment content (percent by volume). Soil samples with hard clods, particularly in the "C" horizon substratum, were not field screened, although estimated coarse fragment content was recorded. Forty soil samples, collected from eleven sample sites, were delivered to Colorado State University's Soil Testing Laboratory in Fort Collins, Colorado, for standard analysis. The list of parameters included all tests that were analyzed for the previous South Taylor/Lower Wilson investigation completed by Greystone in 1999. The current laboratory analysis included: • pH; • Particle size (texture); • Saturation percentage; • Electrical Conductivity (EC); • Soluble Ca, Mg, and Na (meq/L); • SAR (calculation); • Lime estimate • Boron (mg/kg); • Selenium (mg/kg); • Organic Matter (Walkley-Black); • NO3-N; • P (phosphorus), ppm; • K (potassium), ppm; • Zn (zinc), ppm; • Fe (iron), ppm; • Mn (manganese), ppm; and • Cu (copper), ppm. An evaluation of soil suitability was conducted on all major soils in map units in the Lower Wilson mining area. The suitability of soils for use as topsoil during reclamation was determined in accordance with standard procedures in use in Colorado and adjacent states, particularly Wyoming (WDEQ, 1994). These guidelines are generally applicable to Colorado which has no state topsoil and overburden suitability guidelines and are compared to criteria stated in Table 2.04.9-5. The soils field and laboratory data were compared to the standard soil suitability criteria and threshold values to determine the suitability of each soil horizon and map unit. Soils, or portions of the soil profiles, that are considered "suitable" or "marginal" are recommended for salvage. Soils, or portions of the soil profiles, that are considered "suspect" or "unsuitable" were not recommended for salvage. Professional judgment was employed regarding soil suitability if one parameter slightly exceeded the threshold value while all others were considered "suitable". The following parameter threshold values were considered "suspect" or "unsuitable" as used in the suitability evaluation of Lower Wilson soils: • pH <5.0 or >9.0 • EC (conductivity) > 12 • Saturation percent <25% or >80% • SAR (Sodium Adsorption Ratio) > 13 (for soil with >40% clay), > 15 (for soil with <40% clay) South Taylor/Lower Wilson — Rule 2, Page 34 Revision Date: 4/7/17 Revision No.: RN -07