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• swale varies in elevation through area 9/10 possibly allowing one area's elevation high to be cancelled by an elevation low in another area. In summary, if the hypsometric curve method were to be utilized to depict variances and/or similarities of existing topography to approved post-mining topography, the area depicted by the curve would need to be narrowed to exclude these problems. Also, the contour interval spacing that is chosen for area determination would need to be selected based on the degree of topographic variations present in the area. RESPONSE: The MLRD states that the hypsometric analysis has smoothed out topographic irregularities by combining mine areas 31, 7, 51, and 9/10. Furthermore, combining the mine areas and smoothing of irregularities may prevent the hypsometric analysis from detecting differences in approved and existing topography. The mine areas were initially combined to form an area similar to a drainage basin. However, the combined mine areas consisting of areas 31, 7, 51, and 9/10 can be divided into five watersheds. Analysis on a basin scale is justified by the contention by many that a drainage basin is the smallest fundamental hydrologic or geomorphic unit. For instance, • Gregory and Walling (1973, preface) state that the drainage basin, "... is visualized increasingly as the fundamental unit of study in fluvial geomorphology...". Ritter (1978, p. 169) describes basins as, "... excellent fundamental units of geomorphic systems." Chorley et al. (1984, p. 316) point out that the drainage basin,". has been recognized as a viable process-response unit since the beginning of the last century." It is concluded then, that comparison of mine areas smaller than a first order basin is inappropriate because it is a comparison of only a portion of the basic geomorphic system unit. The five watersheds are approximately the size of first-order basins and they extend from the lowermost portions of the mine adjacent to South Foidel Creek to the top of the mine. Approximate drainage divides were drawn between adjacent watersheds that remain fixed on both existing and approved topographic maps so that the same area is measured for both conditions. Contour interval for the analysis is 50 feet except in the area of the swale where contour interval is 25 feet. Hypsometric curves for existing and approved topography within the five watersheds (Figs. 1 through 5) are similar indicating, as did the analysis presented in our report, that spoil material has not been significantly re-arranged by mining. Figure 6 shows the relative locations of mine areas, stream channels, and watershed areas. P1LRD COMMENT: • Swale Area The consultants develop a comparison of a natural steep colluvial slope present in the vicinity of the mine with the oversteepened slopes of the