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• Page 2 Mr. Cass Legal June 23, 1980 At least three reference areas will be required for the mine. Both the aspen and the oakbrush communities will require reference areas. Although the remaining three mountain shrub associations are sufficiently similar to allow the use of a single reference area~you may find, after some preliminary sampling, that you will wish to use two. There is a trade-off which you must consider here: The greater the variation which is encompassed within a mapping unit, the larger the sample size becomes to meet sampling adequacy. At a certain point, you will find that less total sampling will be necessary, if the mapping unit is subdivided. This is a determination which you or your consultant vill have to make. A wet meadow plant community is shown on the vegetation map. You requested that the reference area requirement be waived for this community. In order to grant your request, the areal extent of this community must be small (tenta- tively defined as 2 to 3b or less of the total disturbed area), and the com- munity must not constitute critical or unique habitat. Your permanent program application should include a discussion of the reasons why you feel these criteria are met. • The establishment of reference areas for the H-G Mine is complicated by the extent of the existing disturbance. In order to handle this situation, I would suggest that the sampling program include not only the area which is yet to be disturbed, but same adjacent area as well. A reasonable choice for the study area boundary woul e e perm t oundary. For example, in establish- ing an aspen reference area, your sampling should include not only the single aspen stand which is yet to be disturbed, but also other aspen stands within the permit area which will not be disturbed. This approach will probably increase your variance and therefore your sample size, but you will obtain a better overall estimate of cover and production, which could reasonably be expected to be representative of those aspen stands which have already been disturbed. Increasing the sampling base will also make it easier for you to find an aspen reference area which will satisfy the statistical comparability requirement. You have expressed considerable concern that the reference area you select may not satisfy the statistical comparability requirement. I believe that you are over-estimating the magnitude of this problem. To select a reference area which will satisfy our requirements, you should first study the existing soils, vegetation and topographic maps in order to select an area which is representative based on these criteria. The second step should be a visual inspection. Locations which are obviously unsuitable could be thrown out at this point. Finally, you may wish to do some preliminary sampling from • several potential sites to narrow your choices still further.