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iii iiiiiiiiiiiiiiii 899 June 23, 1980 Mr. Casa Legal Hayden Gulch Coal Co. 333 Quebec St., Suite 8800 Denver, Colorado 80207 RE: Reference Area Selection - H-G Coal Mine Our Pile No. 77-99 Dear Ttr. Legal: The purpose of this letter is to summarize those points which were discussed during our meeting of June 16, 1980, concerning the selection of reference areas for the H-G Mine. Under the permanent program, this Division intends to evaluate proposed reference areas according to the criteria in 4.15.7(3) of the proposed Colorado regulations. You ware given a current copy of 4.15, which contains all recent revisions. As specified in 4.15, the applicant is required to demonstrate statistically that proposed reference areas ire comparable to areas to be disturbed, in terms of ewer and production of herbaceous plants. You are not required to sample cover and production of woody plants. In order to make this comparison, you must sample randomly within each mapping unit and each corresponding refer- ence area. The same sampling methoiolog~es must be used for both. For the determination of sampling adequacy and for the demonstration of reference area comparability, we are currently utilising methods specified in the draft document prepared by the Office of Surface Mining, titled "A Statistical Evaluation of ReveRetation Success on Coal Lands in the faest." In the future, Colorado may develop its ow guidelines. Since virtually all of the vegetation types at the H-G Mine qualify ae "woody plant communities," as defined in the proposed Colorado rep~ulations, the applicable requirements for the statistical demonstration will ba 90R of ttu3 mean with 80Z confidence. Reference areas era required to represent all plant communities identified in the pre-mine inventory. In your case, however, you will probably want to combine some of the original mapping units. specifically the sage-snowberry, chokecherry-saowberry and servicebezry-snoaberTy.