2011-02-28_REVISION - C1994082 (6)

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Yoast Mine SL-3 February 2011 Phase ll Bond Release Request • Table 2. Sample Adequacy Summary for Total All Hit Cover, Phase H Bond Release Block and Extended Reference Area (ERA), Yoast Mine. Area Total All Hit Cover (x) s N nm;n t Phase 11 Bond Release 1 30 Block 57.7 15.6 35 12 . 7 Aspen ERA 159.1 19.4 15 3 1.34 5 Mountain Brush ERA 117.7 19.7 16 5 1.34 1 Sagebrush ERA 66.7 14.0 17 8 1.33 7 Steep Mountain Brush .34 43.5 11 8 15 13 . 5 E Table 3. Sample Adequacy Summary for Allowable All Hit Herbaceous Cover, Phase II Bond Release Block and Extended Reference Area (ERA), Yoast Mine. Area Allowable All Hit Herbaceous Cover x s N nmfn t Phase II Bond Release Block 42.97 15.9 35 24 1.307 Aspen ERA 87.3 21.1 15 11 1.345 Mountain Brush ERA 40.6 11.2 16 14 1.341 Sagebrush ERA 35.8 10.1 17 15 1.337 Steep Mountain Brush ERA 17.5 5.0 15 15 1.345 Sample point locations for the 2010 vegetation sampling used in the Phase II bond release evaluation study are shown on Maps 1 and 2 of the 2010 Yoast Mine vegetation monitoring report (February 2011) prepared by ESCO Associates and included in Attachment XX. The revegetation success evaluations determined that the mean allowable all hit herbaceous cover in the Phase II bond release block was less than the cover standard (described previously). Since the cover sampling met sample adequacy after a minimum of 15 samples were collected, statistical testing using a one-sample t-test was made using the following equation to test the hypothesis of reclamation success for cover (CDRMS 2005 revised rule, 4.15.11 (2)(b)): t - Q-x S- x Where: x = Bond Release Block Sample Mean • Q = 90% of Standard Sx = Standard error of mean [ s / NIn S = Sample standard deviation 6