2012-04-27_REVISION - C2009087 - Laserfiche WebLink

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Area Allowable First Hit Herbaceous Cover (x) s N n min t Phase II Bond Release Block 37.5 14.2 30 25 1.311 Mountain Brush RA 12.8 5.1 15 29 1.345 Sagebrush RA 44.7 8.8 15 8 1.345 Peabody Sage Creek Mine SL -1 Phase II Bond Release Request Table 2, Sample Adequacy Summary for Total First Hit Cover Table 3, Sample Adequacy Summary for Allowable First Hit Herbaceous Cover April 2012 Area Phase II Bond Release Block Mountain Brush RA Sagebrush RA Total First Hit Cover (x) 39.6 71.5 71.1 s 14.3 7.4 7.8 N 30 15 15 nmin 23 2 3 t 1.311 1.345 1.345 'Mean for purposes of sample adequacy calculation; uppermost possible value of the mean, 15.1 taken forward for use in performance standard calculation; see text. The lack of sample adequacy for the mountain brush reference area using allowable first hit herbaceous cover necessitated using an alternative approach as described below to determine the allowable first hit herbaceous cover value for establishing the cover standard. The historical cover success standard developed for the Seneca II Mine, and which applies to PSCM, is an area- weighted average of first hit herbaceous cover values determined from the mountain brush and sagebrush reference areas. Further, the first hit cover is adjusted to allowable as discussed in the Attachment E report. In recent years, CDRMS has required sample adequacy be performed using first hit herbaceous cover data. In the mountain brush, achieving sample adequacy using first hit herbaceous cover data results in very high sample numbers as a result of high variability. The mountain brush structure is dominated by a rather dense woody canopy, but may also have some areas of relatively open canopy to the herbaceous understory. These characteristics contribute to the highly variable first hit herbaceous cover data. Obviously, all hit herbaceous cover data (i.e., multiple hits combined) 8