2011-09-07_REVISION - C1994082 (2)

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• x = Sample arithmetic mean t = The (a =.10) t -table value fora 1 tail t -test, n -1 degrees of freedom (infinite degrees of freedom may be used if n >30) see Rohlf and Sokal (1969) n = Sample size NOTES ON THE COMPARISON OF DATA TO APPLICABLE REFERENCE AREA STANDARDS Upon the formal comparison of cover data from reclaimed areas to applicable performance standards, observed total first -hit herbaceous cover percentage must be adjusted for excessive contribution by annual / biennial species (CDMG 1995, Guidelines Regarding Selected Coal Mine Bond Release Issues, 1 (IV)A(4)). Herbaceous cover values used in such comparisons also must exclude values for species present on the Routt County Prohibited or Restricted Noxious list or that are listed as noxious by the State of Colorado (Colorado Dept. of Agriculture, Division of Plant Industry, Title 35, Article 5.5, 101 -119, Lists A and B of Rules as replaced 2003). Of course given the need to address herbaceous cover, values attributable to woody species are also subtracted. For purposes of assessment of reclamation adequacy, all -hit herbaceous cover data from reference area sampling is used as per Yoast Mine permit provisions. It is also to be noted that the data from the four reference areas is weighted in accordance with the original relative abundance of the types in the pre- mining landscape (Aspen — 24.4 %, Mountain Brush — 48.9 %, Sagebrush /Snowberry 24.0 %, and Steep Mountain Brush — 2.7 %). It was necessary to sample each to adequacy (see below) but in the process of weighting, a reliable estimate of variance is lost. Thus the reference area standard is thereafter in the process treated as a technical standard (i.e. without confidence limits) and one - sample t- testing is used. HYPOTHESIS TESTING APPROACHES For formal hypothesis testing relative to Phase II Bond Release the following procedures were followed: