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SubTerra, Inc. Twentymile Coal Company 3/18/97 Northern Mining District Subsidence • Up-dip and down-dip draw angles of 12° and 21° respectively, which define the limits of subsidence (see Drawing 1).. Subsidence predictions for the Energy Spur railway line and Fish Creek are provided in Tables 2 and 3, and Figures 4 and 5. Predictions have been made for conditions following completion of each panel. 3. Affected Structures, Estimated Impacts. and Remedial Activities There are two principal structures and natural features that will be affected by subsidence in the NMD; the Energy Spur railtrack, and Fish Creek. Impacts to the Energy Spur are predicted to be similar to those experienced during 9-Right and subsequent panel undermining in the Eastern Mining (EMD) district. It is anticipated that required remedial work will be undertaken in conjunction with Union Pacific Railroad using the partial re-leveling method used in the EMD. Impacts to Fish creek and its AVF have been evaluated in a separate report. - 4. Subsidence Monitoring As noted above, CTCC has developed an extensive subsidence data base from monitoring lines positioned to measure start, transverse, and traveling subsidence profiles. No further • systematic subsidence data gathering is therefore warranted. However, it is recommended that CTCC monitor subsidence adjacent to the Energy Spur track, as part of their remedial activities, and along Fish Creek. 5. References SubTema, Inc., 1992. Prediction of Subsidence, Fish Creek AVF Study Area. Report prepared for ACZ and Twentymile Coal company, May, 1992. SubTen-a, Inc., 1993. Prediction of. Subsidence, Eastem Expansion to the Foidel Creek Mine. Report prepared for Twentymile Coal Company, March 23, 1993. Cyprus Twentymile Coal Company, 1994. Semi-Annual Subsidence Report(s), Foidel Creek Mine. Prepared by SubTen'a, Inc. for CTCC and DOGM, June and December, 1994. • ___ P..R 97-04 _, 7 -1-6