2010-03-12_REPORT - C1981019 (8)

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3.0 CONCLUSIONS & RECOMMENDATIONS Conclusion Overall the revegetation at Colowyo evaluated by Cedar Creek in 2009 can generally be considered good to very good, and is typical of reclamation efforts at most western coal mines. There were three units (EP042, EP046, and EP047) that had elevated annual brome populations and may require remediation. The latter two units, EP046 and EP047 are fairly new reclamation, year four and year two respectively, so elevated levels of annual species are not an uncommon expectation. However, these units should be closely monitored to ensure that the annual brome populations do not begin to dominate the revegetation. There are areas marked on maps of each corresponding unit that delineates areas with very sparse perennial cover and dominant annual brome populations that may require remediation. Once annual brome populations reach a certain "threshold" level, it becomes very difficult for perennials to out- compete the annuals, especially in the short-term. EP042, however, may be more problematic since it is now in the seventh year of growth and still exhibits elevated levels of annual bromes. This circumstance likely results from the shrub only seed mix that was used on this unit. All of the perennial grasses have been volunteer species, so they have been slower to establish and compete against the aggressive annual bromes. To the contrary, perennial grasses have increased considerably since 2006, when this unit was last monitored (from 9% to 33% average cover). It is possible this area will need remedial action to control the annual bromes. However, having an occasional revegetation effort that does not perform as expected is a typical occurrence in Western coal mine reclamation. As revegetation units age, they tend to "thicken" with desirable (planted) perennial species and exhibit increased diversity, cover, and production. Given the approval of TR-72 which created more suitable comparisons for vegetation parameters, most areas at Colowyo appear to be progressing along the expected path toward an exceedance of success criteria by the end of the 10-year bond responsibility period. The primary concern is with noxious weed populations (control must be maintained) and annual brome populations exceeding the threshold whereby they become problematic. Recommendation # 1- Apply Plateau or Oust Herbicide to Unit EP042 In most cases at Colowyo, an elevated annual brome population in a unit would warrant a "wait and see" approach to detect the progress or lack thereof of the population. However, the annual brome populations on EP042 have continued to increase from 27.9% in 2006, to 33.5% in 2009. Although perennial cover has increased, it appears that the "threshold" level of annual brome populations may be approaching. This threshold level is the point where the bromes will begin to dominate unless CEDAR CREEK ASSOCIATES, Inc. Page 53 Colowyo Mine 2009 Revegetation Monitoring Report