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Michael G. Altavilla Seneca Coal Company Page 4 November 24, 1998 The Steep Mountain Brush vegetation type is not included as a `'major vegetation type", and this would appear to be an oversight. The discussion and forn~ulas on page 39 and following pages which refer to tour vegetation types need to be updated to reflect incorporation of the South Extension Area, and the vegetation type acreages need to be adjusted accordingly. In summary, narrative needs to be amended to clarify the extended reference area comparison approach, and "major vegetation type" listing and acreages need to be updated as appropriate. 14. Based on narrative on p. 48, Tab 10.2, and Table l OG-4, it appears that sample adequacy calculation employed atwo-tailed t value with n-1 degrees of freedom at 0.2 alpha error probability (80% confidence level). Division guidelines specify that pre-mine sample adequacy evaluation employ a rivo-tailed alpha error probability of 0.1 (90 percent confidence level), unless a maximum sample size of 50 is attained. Although the sample adequacy formula used apparently did not comply with that specified in the guideline, it appears that maximum sample size of 50 was attained for all production samples, and that sample adequacy at the two-tailed, 90% level was met for cover for all types, with the exception of western wheat grass/alkali sagebrush affected cover, and steep mountain brush affected cover. For the former, 15 sample observations were made, while sample adequacy formula indicates 21 transects would have been required. For the latter type, 15 transects were run, with the sample adequacy formula indicating that 22 would have been required. In both cases, reference area cover sample mean exceeded the affected area sample mean, and it is very unlikely that more intensive sampling would have altered the determination regarding suitability of the extended reference area. Sample adequacy calculations for woody plant density were not checked in detail, although it would appear that sample adequacy at the 90% level may not have been achieved for several of the sampled types. This is not considered to be a significant flaw, since the woody plant success standard is not based on pre-mine data or reference area comparison. In general, data presented is sufficient to document the characteristics of the pre- mine plant communities and the comparability of the affected and reference