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level of confidence. Frequency distributions of the existing and <br />• approved slopes (Fig. 2. 1) are also similar. A second sampling <br />procedure was used to distinguish between hillslopes and valley side- <br />slopes. Hillslopes on existing and approved topography are not <br />significantly different at the 95% confidence level. Frequency <br />distributions are also similar (Fig. 2.2). <br />Existing valley side-slope gradients are less than approved <br />gradients and this reduction in gradient should improve stability of the <br />existing topography. Valley side slopes are significantly different at <br />the 95% confidence level. Frequency distribution of valley side slopes <br />are shown in Figure 2.3. <br />2.2.2. Hypsometric Curves <br />• Hypsometric analysis is a means of determining the distribution of <br />mass within a watershed (strahler, 1952). A planimeter was used to <br />measure the area of the watershed above a given contour on a topographic <br />map. Elevation of each contour measured was plotted against area above <br />the contour for both existing and approved conditions. <br />Areas 9/10, 51, 7, and 31 are contiguous and, therefore, they were <br />treated as a single mine area (Fig. 2.4). Area 41 is separated from the <br />other mine areas by an undisturbed drainage valley and it has been <br />analyzed separately (Fig. 2.5). <br />The curve pairs in Figures 2.4 and 2.5 are similar indicating that <br />spoil has been replaced so that the area above each contour, either <br />existing or approved, is very similar. This strongly suggests that <br />approximate original contour has been achieved throughout the mine area. <br />r 1 <br />8 <br />