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STATE OF COI.O RADO RiC H.~Rn D~L•AGt, f, rn~emm III III III III IIII III <br />DEPARTMENT OF NATURAL RESOURCES <br />D. Monte Pascoe, Executive Director <br />MINED LAND RECLAMATION <br />423 Centennial Building, 1313 Sherman Street <br />Denver, Colorado 80203 Tel. (303) 866-3567 <br />David C. Shelton <br />Director <br />July 22, 1982 <br />Mr. Henry Barbe <br />Powderhorn Coal Company <br />P. O. Box 1430 <br />Palisade, Colorado 81526 <br />RE: Roadside and Cameo Vegetation Survey <br />Our File NC-041-81 <br />Dear Mr. Barbe: <br />As was discussed in phone conversations with Dan Mathews and myself on <br />July 20, 1982 and July 21, 1982, respectively, the vegetation information <br />submission dated July 9, 1982 is acceptable to the Division with four <br />minor clarifications. <br />First, up to 50 herbaceous production plots may be required unless sampling <br />adequacy is achieved with fewer samples. Second, the success criteria for <br />woody plant density should be set after the collection of vegetation data. <br />Establishment of shrub densities equal to 90°0 of the reference area mean <br />may not be practical or desirable. Third, the sampling adequacy formula <br />should be changed to read; <br />M=t2 s2 <br />~ a <br />By adding the x term (sample mean) the number of samples required to meet <br />sampling adequacy will be greatly reduced. Fourth, the term definitions <br />below the sampling adequacy formula should be changed to read; <br />M = the minimum number of observations needed <br />t = the two-tailed t distribution value at the 90% confidence level. <br />S2= the variance 'es ti mate obtained from sampliny. <br />d = the level of accuracy desired for the estimate of the mean, and <br />z = the sample mean. <br />The vegetation sampling at Powderhorn should proceed as planned, as soon as <br />possible. <br />If you have any further questions, please feel free to contact me. <br />ncerely~ <br />PJ~--- <br />cc: Dan .Mathews m Herron <br />Bi11 Tate Reclamation Specialist <br />JH:ys <br />