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• <br />• <br />• <br />• <br />r <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />r <br />• <br />• <br />s <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />• <br />2.4.2 West Pit <br />Tables 6 and 7 exhibit the average cover and composition of vegetation found on the one West Pit <br />unit evaluated in 2007. Unit WP008 (7 growing seasons) has progressed with mixed results toward <br />satisfaction of required bond release criteria. Perennial cover (52.7%) and production (1,166.6 pounds <br />per acre) easily passes comparisons with the reference areas. Diversity of perennial grasses and forbs (5 <br />perennial grasses and 0 perennial forbs) fails the standard of 3 perennial grasses and 1 perennial forb <br />with between 3% and 50% relative cover. Woody plant density in WP007 is modest at 520 woody plants <br />per acre, which is below the present standard of 90% of 1,000 woody stems per acre. See Appendix AA <br />-Section 6.3 for a discussion on options and recommendations with regard to woody plant density. <br />Annual bromes currently represent 19.1% cover in this unit, and any pockets or similar concentrations <br />should be monitored to gauge if they are expanding or shrinking. If monitoring reveals expansion, use of <br />the herbicide Plateau is recommended. <br />Rio Tinto Energy America/Colowyo Mine <br />Page 31 <br />Revegetation Monitoring - 2007 <br />