2020-07-09_REVISION - C1981028 (12)

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Coors Energy Company: Keenesburg Mine Technical Revision 47 Modification of Reclamation Success Standards In 2019, data were collected in an undisturbed area on the mine property at the same time as the reclamation to evaluate the current composition of warm and cool season species. The sampled area has been managed to prevent livestock grazing for over twenty years and has received wildlife use similar to the reclaimed areas. While this area did have a large component of cheatgrass (25% of the relative cover), cool-season perennial grass species were not observed (Table 2). Table 2: 2019 Undisturbed Area Data Average Absolute Average Relative Scientific Name Common Name Cover (%) Cover (%) Grass: Annual Native 1 species 0.4 1.3 Grass: Annual Introduced Bromus tectorum cheatgrass 11.8 25.7 Grass: Perennial Desirable(Warm) Andropogon hallii sand bluestem 3.0 6.8 Bouteloua gracilis blue grama 0.2 0.4 Calamovilfa longifolia prairie sandreed 5.8 13.1 Panicum virgatum switchgrass 0.4 0.8 S orobolus cryptandrus sand dro seed 14.0 30.8 Subtotal 23.4 51.9 Forbs: Annual&Biennial Native 5 species 4.8 10.5 Forbs: Perennial Native 5 species 1.6 3.8 Shrubs/Succulents:Perennial Native 3 species 3.0 6.8 Total Vegetation Cover' 45.0" 144;11 4 SEED MIXTURE The approved reclamation seed mixture for Keenesburg Mine includes seven warm season perennial grass species and two cool season perennial grass species (Table 3). If this seed mixture's composition was expressed exactly with no other species establishing in the reclamation, there would be one cool season species and seven warm season species with greater than 3% and less than 40% of the relative cover. There are seven warm season grass species included in the seed mixture to meet the warm season standard when only three are needed. This mixture increases competition for plant available soil moisture and serves to decrease the likelihood of cool season species establishment. 3 July 2020