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0 3.0 GEOTECHNICAL FRAMEWORK <br />In this section, the geologic setting of the Hubbard Creek mining area is reviewed, <br />followed by a description of the rock mechanics testing program and joint surveys within <br />the North Fork Valley. Procedures suggested by the International Society of Rock <br />Mechanics (ISRM) are used to characterize rock mass quality for select overburden <br />stratigraphic units, which indicate mostly fair-to-good rock types capped by semi- <br />consolidated colluviums. <br />3.1 Geologic Setting <br />The Somerset Coal Field is located on the southeastern margin of the Piceance Basin, <br />which lies north of the Gunnison Uplift, west of the Elk Mountains, east of the <br />Uncompahgre Uplift, and south of the White River Uplift. Six primary coal seams lie <br />within the Somerset Coal Field, ranging from 10 ft thick on a single bench of coal to over <br />20 ft where one or more seams merge (Maleki and others 1997) (figure 2). An estimated <br />1.5 billion tons of bituminous coal are within the Somerset field. Coal seams B, C, D, E, <br />and F have been mined historically in this basin. The coal seams contain a very well <br />developed cleat set oriented N58° to 75° E (Carroll 2003). <br />The regional structural dip of the Mesa Verde Formation is 3° to 5° to the north- <br />northeast. The predominant jointing of sedimentary rocks is N 68° E to N 74° E in the <br />basin, with secondary jointing at N 18° W (Carroll 2003) to N 35° W. Regional joint <br />patterns were mapped by Tifft (1995) and Carrol (2003). <br />During extraction of the D1 to D9 panels, BRL geologic staff studied faulting near the <br />study area using both surface and underground observations. Only one known fault has <br />surface expression in the Hubbard Creek drainage area. This fault was observable along <br />the west side of the drainage only after the D5 panel had been extracted directly beneath <br />the outcrop exposure (Hunt 2005). At the Bowie No. 2 Mine to the west, both normal and <br />strike-slip faults have been encountered. The southern portion of the D6 panel is <br />traversed by a N 80-90° E left-lateral, strike-slip fault system. The system is a complex <br />Maleki Technologies, Inc. Page 6