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Introduction <br />The 1999 Subsidence Report is submitted in accordance with Section 2.05.6(c) of <br />• Powderhorn Coal Company's Mining and Reclamation Permit. The stipulation requires an annual <br />report of the results of subsidence monitoring inspections. Additional information contained in the <br />report includes a description of the local terrain, vegetation and geology. <br />Powderhorn Coal Company owns and operates two mines in DeBeque Canyon near the <br />eastern end of the Grand Valley, in Mesa County, Colorado. The Roadside South Portal Mine was <br />idled in 1996. The mine remains idle, ventilated and pumped to allow future access for recovery <br />and inspections. The Roadside North Portal Mine produced a total of 350,810 tons of raw coal <br />during 1999 from one mining district disturbing an areal extent of approximately 79 acres. The <br />Roadside North Portal Mine was idled December 2, 1999, and remains ventilated, and pumped for <br />future recovery and inspections. <br />The investigation of subsidence related effects on the surface of the mine property <br />concentrates on the area mined during the last two years, 1998 through 1999. This area includes <br />only the 2nd West section of the Roadside North Portal Mine. The Roadside South Portal has <br />been idle for over 2 years with no mining projected for next year. <br />Topography and Vegetation <br />The topography in the mine area consists of narrow valleys, overly steep canyon walls and <br />small mesas on the northwestern flank of the Grand Mesa. The Colorado River and its flood plain <br />bisect the permit area and provide a corridor for the Union Pacific Railroad. The surface terrain <br />varies from the nearly flat flood plain to nearly vertical cliffs of massive sandstone. The vegetation <br />also varies from Saltbush Desert and Riparian Habitat in the lower elevations to Pinyon/Juniper <br />Woodland in the higher elevations. The effectiveness of the visual inspection (or pedestrian <br />survey) of the ground surface for subsidence features is limited by both topography and vegetation. <br />Geology <br />The coal seams mined in the area are contained with the Mr. Garfield formation of the <br />Upper Cretaceous and Tertiary Ages. The river bottom and flood plain contain sand and gravel <br />deposits of Quaternary age. The Cameo seam in its Upper and Lower benches (respectively the <br />Cameo C and Cameo B Seams) are mined in the Roadside North Portal Mine, while only the <br />Cameo B Seam is mined in The Roadside South Portal Mine. <br />Other seams present within the area are the Palisade and the Carbonera. Both are of <br />• limited economic interest. These seams tend to be thin, lenticular and of poor quality. Additional <br />1999 Subsidence Report Page 2 12/29/99 <br />