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I. INTRODUCTION <br />1 <br />This report has been prepared in support of an application for Phase II bond release for <br />two areas (Area 1 and 2) within the permit area of the New Horizon Mine (Colorado <br />Division of Minerals and Geology permit C-81-008), owned and operated by Western <br />Fuels-Colorado. Documented within is information relative to the erosion and <br />sedimentation condition of Area 1, Area 2, and the Upland Sagebrush Reference Area <br />of the mine. Quantitative sampling of vegetation and soils was performed in <br />compliance with Colorado Mined Land Reclamation Board Surface Coal Mining Rules <br />and Guidelines and current botanical and soil science methods. Field sampling was <br />conducted between July 5 and 8, 1993 by Savage and Savage and observed by staff of <br />the Colorado Division of Minerals and Geology. Analysis was conducted by Mr. Greg <br />Lewicki, P.E. of Greg Lewicki and Associates. <br />II. METHODS <br />SEDIMENTOI.OGY DEMONSTRATION <br />The two reclaimed areas and the Upland Sagebrush Reference Area are shown on <br />Figure 4 of this report. The two reclaimed areas must be shown to wntribute equal or <br />less sediment to the receiving waters downstream in order to satisfy the Phase U bond <br />release. This is done by identifying equal areas from the three sites, and through the <br />use of computer modeling (SEDCAD), determining the amount of sediment eroded <br />' from each of the areas for a given storm. In this case, the storm used is the 10 year - <br />24 hour storm for the area comprising 1.6 inches of rain. <br />' Figure 4 shows sub-areas of 2.0 acres at each of the two reclaimed areas (Area 1 and 2) <br />and the Upland Sagebrush Reference Area. Each of these sub-areas has approximately <br />the same slope, elevation, aspect, and geomorphic condition. There are no drainages <br />present in the sub-areas and sheet flow will occur during the model storm event. The <br />sub-areas have been carefully selected so that they allow a fair comparison for <br />sedimentology purposes. <br />CN NUMBERS <br />' Tables 2, 3 and 4 show the breakdown of the recently tested vegetative cover at the <br />three areas. Using these cover data and the overall Hydrologic Soil Group of the sites <br />as type "C", Table 5 is used to determine the CN numbers for the sites. This table was <br />' taken from "Procedures for Determining Peak Flows in Colorado" by the SCS. <br />I 26 <br />