2020-07-09_REVISION - C1981028 (12)

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Coors Energy Company: Keenesburg Mine Technical Revision 47 Modification of Reclamation Success Standards Prevailing weather patterns in the region are variable with one of four typical patterns expressed annually: 1. Cooler temperatures and increased spring precipitation, 2. Warmer temperatures and more monsoonal summer precipitation, 3. Wet years with a mixture of both above scenarios; and 4. Dry years with warmer temperatures and little or no precipitation. Scenario 1 above favors cool season grass germination and establishment. Scenarios 2, 3 and 4 favor warm season grass over cool season grass germination and establishment. Therefore, prevailing weather patterns in the region favor germination and establishment of warm season grasses. Also, warm season grass physiology is better adapted to the weather patterns in this region (i.e., typically deeper adventitious root systems and C4 photosynthesis). Because prevailing site conditions are unfavorable for cool season grass species establishment and warm season grasses are better adapted to the weather in this area, there is very little chance for the reclamation community to meet the current composition standard. Table 3: Approved Reclamation Seed Mixture Species Common Name %by Seed Grass: Perennial Cool-Season Achnatherum hymenoides Indian ricegrass 6% El gnus lanceolatus thicks ike wheatgrass 2% Subtotal 8% Grass: Perennial Warm-Season Andropogon hallii sand bluestem 10% Bouteloua curtipendula sideoats grama 12% Bouteloua gracilis blue grama 18% Calamovilfa longifolia prairie sandreed 18% Panicum virgatum switchgrass 8% Schizachyrium scoparium little bluestem 6% Sor hastrum nutans Indiangrass 11% Subtotal 82% Forb•Perennial Ratibida s . Prairie Coneflower 10% Total ll0% Cool season grasses were not observed in 2019 in the undisturbed areas adjacent to reclaimed lands. This serves to confirm that cool season species are ill-adapted to this rangeland. It also indicates that a cool season seed source for volunteer introduction into the reclamation is nominal or absent. The current composition standard was based on the OSRA and several of the older reclamation areas (seeded in 1995 — 1999). The data provided for these areas in TR37 primarily included two native cool season perennial species in the OSRA (green needlegrass and western wheatgrass, Pascopyrum smithii) and two more native (Indian ricegrass,Achnatherum hymenoides and 4 July 2020