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• 4.0 SUBSIDENCE IMPACTS <br />During the first half of 2003, subsidence survey data was collected periodically from established monuments on <br />the Union Pacific Railroad and the YVEA power line in areas underlain by gate roads or panel centers doting <br />periods of mining in the 14 Rt longwall panels. During the second half of 2003, subsidence survey data was <br />collected periodically from established monuments on the Union Pacific Railroad in areas underlain by gate roads <br />or panel centers during periods of mining in the 15-Right longwall panel. This data was presented to DMG in <br />detail in the two semiannual subsidence reports for 2003 (First Half 2003 Subsidence Survey Report, and the <br />Second Half 2003 Subsidence Survey Report). <br />Structures remained essentially unaffected during the period with the exception of the predicted impacts to the <br />Union Pacific Railroad and Fish Creek As is reflected in the data and on the associated subsidence map, [he 15- <br />Right longwall panel did not directly undermine the Walcott, Hayden-Gore Pass and Western Area Power <br />Administration power lines and Foidel Creek during the second half of 2003. No adverse impacts, i.e. imminent <br />failure of structure, were evident with regard to these structures. <br />Hydrologic monitoring did not indicate significant impacts to Fish Creek, however elevated iron concenvations <br />were detected in surface water quality in June 2003 (which subsequently dropped during an August 2003 <br />sampling episode). In addition, iron concentrations appeared elevated in related alluvial wells during August <br />• water quality sampling. Hydrologic monitoring of these sites will continue in 2004, and this anomaly will be <br />monitored and assessed. <br />Fish Creek: has been undermined and subsided by TCC's mining of the 13 Rt longwall panels. A post mining <br />survey of Fish Creek in areas underlain by the 13 Rt gate road or panel center was performed in July/August <br />2002. The final subsidence profile for Fish Creek over the 13 Rt panel is submitted as Figure 237 of this AHR. <br />Subsidence monument surveys disclosed no unusual developments during the reporting period. Projected <br />subsidence magnitudes and draw angles were within the anticipated ranges previously documented for [he area. <br />Structures remained essentially unaffected during the period with the exception of the predicted impacts to the <br />Union Pacific Railroad and YVEA power line poles. No adverse impacts, i.e. imminent Failure of structure, were <br />evident with regard to these structures. <br />During the summer of 2002, subsidence ponding became evident in the immediate area of surface site 1002. This <br />area was be surveyed in 2003. The 14 R[ longwall panels will undermine Fish Creek in November 2002. <br />Potential impacts will be surveyed in 2004. <br />Foidel Creek: has been undermined and subsided by TCC's mining of the 9 Rt, 8 Rt, 7 Rt, and to a very limited <br />extent the 6 Rt panels, and extreme eastern end of panel 12 Rt. Mining in 12 Rt was completed in 2001, and <br />• subsequently sealed in September 2001. Figure 135 provides the location of the creek in relation to the <br />previously mentioned longwall panels. The figure also reflects [he ponding that occurred over the panels. As <br />noted on Figure 135, the largest area of ponding resulted from mining of 7 Rt. Pond 4 had the greatest surface <br />16 <br />