2013-04-19_REPORT - C2009087 (7)

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NOTES ON THE DEVELOPMENT OF REFERENCE AREA — BASED PERFORMANCE STANDARDS Corrections for Noxious Weeds and Excess Annuals Upon the formal comparison of cover and production data from reclaimed areas to applicable performance standards, observed total first -hit herbaceous cover percentage and collected production, must be adjusted for excessive contribution by annual / biennial species (i.e. no more than 10 percent relative cover or production, CDMG 1995, Guidelines Regarding Selected Coal Mine Bond Release Issues, 1(IV) A(4)). Herbaceous cover and production 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). For purposes of assessment of reclamation adequacy, first -hit herbaceous cover data from reference area sampling is used as per PSCM Mine permit provisions. Upward Adjustment of the Mountain Brush Cover Standard Sample adequacy for total vegetation cover was achieved for the reference areas and BRB PSCM -2. For total allowable herbaceous cover, adequacy based on first -hit values was achieved for BRB PSCM -2 and the Sagebrush Reference Area, but it was not for the Mountain Brush Reference Area. In consideration of the lack of a sample size sufficient to detect a 10 percent reduction in the mean with 90 percent confidence (i.e. sample adequacy), the upper limit of the possible values of the true mean (with a sample size of 18 in 2012) was determined. This can be done either by calculating the confidence interval for 90% confidence and adding it to the mean or by way of rearranging the sample adequacy formula and solving for the detectable percent reduction then adding that to 100% and multiplying by the mean. This is demonstrated in the Discussion section below. It is also to be noted that provisions of the permit include the weighting of the data from the two reference areas in accordance with the original relative abundance of the types in the pre- mining landscape (83% mountain brush, 17% sagebrush /snowberry). In the process of weighting, a reliable estimate of variance is lost. Thus the reference area standard thereafter in the process is 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 III Bond Release the following procedures were followed: Cover and Production Phase III Revegetation success for cover and production will be demonstrated by one of following statistical approaches. 5