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t ~ 4 sss STATE OF COLORADO DIVISION OF MINERALS AND GEOLOGY Depanmem of Nzwral Resources 1313 Sherman St.. Room 21 5 Denver, Colorado 80203 Phone: 1303 866-3567 FAX:~3031832-8106 July 27, 1995 Mr. Richard Mills Cyprus Yampa Valley Coal Corporation 29587 Routt County Road ,# 27 Oak Creek, Colorado 80467 RE: 1995 Reclamation Sampling Program Dear Mr. Mills: ~~~ DEPARTMENT OF NATURAL RESOURCES Roy Romer Governor dames S Lochhead Eeecwive Dueaor M¢hae~ a Long Dims~on Dimcloi The Division has reviewed your proposed reclamation sampling program for 1995. As we discussed during my June inspection and as included in that inspection report, the proposed sampling program is acceptable as submitted. This letter is just additional documentation that the proposal was reviewed, both in the office and the field, and meets the requirements of the Division's bond release guidelines for conducting vegetation sampling. Cyprus' rationale for comprising the reclamation blocks appears to be sound and to follow closely the Division's criteria for bond release area delineation. The proposed blocks are Block E and W in the Mine 2 area, Block F in Eckman Park and Block N at Mine 3. The actual sampling methodology is consistent with what has been conducted in the past including 50 meter transects with 10 observations every 5 meters for cover and five 1/4 meter squared production plots per transect. The sample design would appear to be an improvement with respect to collecting more samples if necessary to meet adequacy and the total random design is acceptable. Since the guidelines are now final, there is one area that CYCC should be aware of with respect to calculating sample adequacy if hypothesis testing is required. The formula that is used in that instance is from Kupper and Hafner(1989) and is located on page 20 of the Bond Release Guidelines. In this formula the t-value is a summation of two values (a=.10 and a=.25 t-table values for a single tailed t-test with n-1 degrees of freedom). Using this formula will probably increase the number of samples required to meet sample adequacy. However, this formula is only required if Hypothesis Testing is required which is when the reclaimed area is less than 90$ of the reference area. If the reclaimed area is equal or greater than 90$ of the reference area, the standard formula is used and t is the t-table value for a SINGLE TAILED t- test when a=0.10 with n-1 degrees of freedom.