2009-03-27_REPORT - C1981019 (7)

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2.0 RESULTS 2.1 Overall Summary Overall, a total of 68 plant species were observed within the 7 revegetated areas, whereas 49 plant species were observed in the 2 reference areas evaluated in 2008. These consisted of 24 grass taxa, 35 forbs, 0 sub-shrubs, and 9 shrubs in the revegetation and 15 grass taxa, 23 forbs, 4 sub-shrubs, and 7 shrubs in the reference areas (see Table AB-1 in Appendix AB). Table AB-1 indicates all taxa observed during fieldwork and is the only table that indicates 1) common names, 2) historic scientific nomenclature, and 3) most current taxonomic nomenclature. Remaining tables do not indicate this latter category. On average, 33 unique plant species are observable in any given revegetation unit and 33 in the references areas as well. Among these taxa are an occasional noxious or invasive weed such as musk thistle or Japanese brome (and/or cheatgrass), with the latter occasionally existing as more notable patches. In 2008, there were no units in year two or year four, therefore all units monitored exhibited 7 or more growing seasons with one unit in its first growing season. An analysis of the ground cover variable (Chart 3) indicated that five of the six areas of older reclamation (7 or more years of age) exceed the success criterion based on 2008 reference area values. One unit in west pit (WP010) does not pass the 2008 standard. On the other hand, Table 1 and Chart 4 indicate success with regard to production on all six of the revegetated units that are 7 or more years of age. With regard to diversity, Colowyo's revegetation efforts appear to be reasonable as indicated on Table 3 and Chart 6. Diversity tends to increase with the age of reclamation and in most cases should be sufficient for bond release testing by the time they are of sufficient age for such testing (years 9 and 10 of the bond responsibility period). As indicated on Chart 6, four of the six areas monitored in 2008 would pass such testing. Failures are a result of reclamation not exhibiting a dominant perennial forb. However, such failures may simply be due to random sampling error (i.e. sample placement). This analysis suggests that Colowyo is in a reasonable position with regard to the diversity variable. Contrary to the aforementioned three variables, woody plant density at Colowyo remains somewhat problematic and will continue to do so until new reclamation metrics pursuant to TR-72 are implemented. Perusal of Chart 5 and Table 2 in comparison to the current success standard of 1000 stems per acre reveals that all monitored areas fall short (when considering density on a unit average basis). As stated in the 2003 report, it is Cedar Creek's recommendation that Colowyo continue to pursue a program of modification (TR-72). This program provides several avenues for correction of the woody plant density Rio Tinto Energy America/Colowyo Mine Page 5 Revegetation Monitoring - 2008