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1.0 INTRODUCTION <br />This report was prepared at the request of Bowie Resources, LLC (BRL), for an <br />evaluation of surface subsidence mechanics and determination of typical deformation <br />expected at the Dove Gulch study area in the North Fork Valley, Delta County, Colorado. <br />Specific objectives were as follows: <br />• Description of expected type of subsidence and associated mechanisms; <br />• Calculation of subsidence profiles over afour-panel longwall block in the Upper <br />B Seam (UBS) using both site-specific and regional subsidence measurement <br />results. <br />The study area is located in the North Fork Valley, Delta County, Colorado, near the <br />existing operations of the BRL No. 2 Mine. Longwall mining is generally the most <br />• environmentally attractive method to mine coal. It minimizes damage to the surface by <br />permitting gradual subsidence of overburden strata over mined-out areas while, at the <br />same time, satisfying BLM requirements of maximizing economic recovery of coal <br />resources (Maleki and others 2001). <br />BRL is planning to mine coal reserves from the Dove Gulch study area using the <br />longwall method in the Upper B Seam at a depth of 800 to 2,300 ft. Existing mine plans <br />call for the extraction of the reserve using an extraction height of up to 12 ft within <br />longwall panels. Subsidence calculations (consisting of vertical movements and <br />horizontal strains) were completed for four longwall panels of interest to this study (B8 <br />through B11), as illustrated in figure 1. Important to these calculations are measured <br />subsidence over the longwall panels in the D Seam (D1 through D9) (figure 2). <br />This report is prepared in five sections. After this introduction, conclusions and <br />recommendations from the study are presented in section 2.0, followed by a discussion of <br />• subsidence mechanisms in section 3.0. Geologic conditions and subsidence <br />Maleki Technologies, Inc. Page 2 <br />