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• s2 = sample variance <br />d = 0.1 (0.15 for woody plant) (level of precision or desired detectable reduction) <br />x = sample mean <br />Confidence Limits <br />Confidence limits for comparisons to reference areas and technical standards were calculated <br />using a 1-tailed t-value for alpha error probability of 0.10 at (n-1) degrees of freedom multiplied by <br />the standard error of the mean of the sampled area. <br />C.I. = tt s <br />4n <br />[ - I <br />Performance Standards for Herbaceous Production and Woodv Plant Densit <br />HERBACEOUS PRODUCTION: For purposes of comparison only, herbaceous production <br />performance standards were calculated in accordance with procedures contained in the Seneca <br />IIW permit. A line that indicates 90 percent of this standard has been placed on Figures 1a and 2 <br />• for informational purposes. At such time as bond release is formally sought, revegetation will be <br />considered successful for cover when mean cover for a bond release block is at least 90% of the <br />calculated success standard or approved technical standard. <br />WOODY PLANT DENSITY: For purposes of comparisons in this document, general (background) <br />woody plant density at the Seneca IIW Mine is evaluated using a technical standard of 200 <br />shrubs per acre. Shrub concentration areas such as may be included in eventual bond release <br />blocks are judged by a standard of 2000 stems per acre. Of shrub concentration areas that have <br />been planted at the Seneca IIW Mine, some were sampled in 2006 to document the status of <br />plantings. Those that were not sampled in 2006 were sampled in 2007and 2008 for the same <br />purpose. <br />Climatic Data <br />Precipitation data were collected at the Seneca IIW Mine during the period 1990 through 2008. <br />For years 1982 through 1989, SCC provided precipitation data from the nearby Seneca II Mine. <br />Since the data record for Seneca II exists for only 25 years, the long term average (56 years) of <br />monthly precipitation data from the Western Regional Climate Center (WRCC) for the nearby <br />• town of Hayden was used as an appropriate base for comparison. Information on degree-days <br />was based on temperature data from the met station 2 at the Seneca IIW Mine. <br />5