2019-04-16_REVISION - C1981019 (3)

Home Browse Search

RULE 4 PERFORMANCE STANDARDS Rule 4 Performance Standards 4-53 Revision Date: 4/16/19 Revision No.: MR-200 Composite soil and overburden samples were taken from each treatment at each mine. Overall, the soils (topsoil and spoil) at all three-mine sites have good physical and chemical properties. Soil pH ranges from 6.9 to 7.8, macronutrients appear to be adequate for sustained plant growth, organic matter contents are relatively high (3.7% to 6.3%), salt levels are low (EC ranges from 0.6 to 1.6 mmhos/cm and SAR ranges from 0.3 to 1.8), cation exchange capacity (CEC) is in a normal range, and textures are clay loam and sandy clay loam. Overall, topsoil and spoil at all mine sites have favorable characteristics and provide a suitable plant growth medium. At Colowyo, soil pH ranges from 7.5 to 7.8, macronutrients appear to be adequate for sustained plant growth, organic matter contents are relatively high (3.7% to 4.8%), salt levels are low (EC ranges from 0.6 to 1.2 mmhos/cm and SAR ranges from 0.3 to 1.6), cation exchange capacity (CEC) is in a normal range, and textures are clay loam and sandy clay loam. The detailed soil and overburden analysis for the Colowyo Mine is provided below. Parameter Plot 1a Plot 2b Plot 3c Plot 4d Plot 5e pH 7.5 7.5 7.5 7.7 7.8 % OM 4.1 4 4.8 4.1 3.7 NH4-N mg/kg 4.9 4.6 6 6.1 8.7 NO3-N mg/kg 24.1 19.1 22.3 13.7 18.1 P mg/kg 15 9.6 12 7.8 29 K mg/kg 191 210 201 95.1 105 Ca meq/L 4.9 4.1 4.4 3.5 5.5 Mg meq/L 2.6 1.6 2 2.4 4.1 Na meq/L 0.8 0.6 1.3 1.9 3.5 K meq/L 0.2 0.5 0.4 0.2 0.2 EC mmhos/cm 0.7 0.6 0.7 0.7 1.2 SAR 0.4 0.3 0.8 1.1 1.6 CEC meq/100g 26.8 22.1 22.9 27 23.3 % Sand 41 51 48 39 41 % Silt 23 23 23 23 25 % Clay 36 26 29 35 35 Texture clay loam sandy clay loam sandy clay loam clay loam clay loam aPlot 1 = 18 inches of topsoil, strip seeding in alternate rows. bPlot 2 = 6 inches of topsoil and surface manipulation, seeded with native shrubs and low competitive forbs. cPlot 3 = 6 inches of topsoil, strip seeding in alternate rows. dPlot 4 = Non-topsoiled spoil, strip seeding in alternate rows. ePlot 5 = Non-topsoiled spoil, seeded with unpalatable native shrubs and low competitive forbs and grasses. To evaluate the impact from wildlife browsing, elk proof fencing was constructed on one-half of each treatment. Colowyo Mine Specific Field Trial