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Additional unsuitability threshold values for overburden include: Nitrate Nitrogen >50 ppm
<br />for aquifer restoration if involved, Molybdenum >1.0 ppm (marginal rated), Acid/Base
<br />Potential <-5.0 Toms CaCO3 equivalent/1000 tons, Arsenic >2.0 ppm (marginal rated), and
<br />Organic Carbon >10% (WDEQ, 1996).
<br />The recommended salvage depths are discussed in the map unit descriptions in the
<br />following results section. Topsoil volumes for salvaged soils are included in the project
<br />reclamation plan.The soil profile descriptions for all sampled soils include added
<br />information for each soil horizon taken from the soils laboratory data. Soil reaction (pH),
<br />electrical conductivity (EC), and sodicity (Sodium Adsorption Ratio, SAR) values are added
<br />to the profile description so that the reader can see whether a particular soil, or individual
<br />horizons within a soil, have low or high values concerning pH, EC, and SAR. A modifier
<br />phrase is also added next to these values to indicate relative status, as follows.
<br />For pH values, modifier terms are taken from a standard NRCS source (Soil Survey Staff,
<br />1993) as follows: Ultra Acid (<3.5), Extremely Acid (3.5-4.4), Very Strongly Acid (4.5-5.0),
<br />Strongly Acid (5.1-5.5), Moderately Acid (5.6-6.0), Slightly Acid (6.1-6.5), Neutral (6.6-7.3),
<br />Slightly Alkaline (7.4-7.8), Moderately Alkaline (7.9-8.4), Strongly Alkaline (8.5-9.0), and
<br />Very Strongly Alkaline (>9.0).For EC values, modifier terms are also taken from this
<br />standard NRCS source (Soil Survey Staff, 1993) as follows: Non Saline (0-2), Very Slightly
<br />Saline (2-4). Slightly Saline (4-8), Moderately Saline (8-16), and Strongly Saline (>16).For
<br />degrees of sodicity (SAR), modifier terms have been constructed based on a review of
<br />recent NRCS material as well as well as experience with site-specific soils in the Big Horn
<br />Basin, as follows: Non Sodic (0-2), Slightly Sodic (2-8), Moderately Sodic (8-15), Highly
<br />Sodic (15-30), and Very Highly Sodic (>30).
<br />3.0 RESULTS
<br />For soil purposes, the McClane Canyon Mine Expansion Area is within a "mesic" soil
<br />temperature regime and an "aridic bordering on ustic" soil moisture regime. The mean
<br />annual soil temperature is about 48 to 53 degrees F., with the mean summer soil
<br />temperature of 65 to 75 degrees F. The mean annual precipitation is about 12 inches, and
<br />the average frost -free period is about 90 to 125 days (NRCS, 1998 and Alstatt, 2003).
<br />Elevations within the gently sloping project area are about 5,365 feet(MSL) in the southern
<br />part to about 5,480 feet (MSL) in the northeast part.Elevations increase to about 5,600 feet
<br />in the lower cliffs on the east side of the area. The project area is currently used as wildlife
<br />habitat and minor rangeland and is adjacent to Disturbed Land in the northeastern part.
<br />The project area has been previously mapped to the less detailed Order 3 level by the
<br />Natural Resources Conservation Service as part of the "Soil Survey of Douglas Plateau
<br />Area, Colorado, Parts of Garfield and Mesa Counties" (Alstatt, 2003). In that survey, the
<br />entire current Soils Study Area was mapped as "Cameo fine sandy loam, 1 to 6% slopes"
<br />(Map Unit 15), with the exception of the steep cliffs area on the east side that were mapped
<br />as "Rock Outcrop-Torriorthents complex, 15 to 90% slopes" (Map Unit 61) (Alstatt, 2003).
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