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FIRST-HALF 2004 SUBSIDENCE REPORT I. Survey Data: During the first-half of 2004, subsidence survey data was collected periodically from established monuments on the Union Pacific Railroad (UPRR) in areas underlain by gate roads or panel centers during periods of mining in the 16-Right (Panel No. 16) longwall pane]. As reflected in the data and on the attached subsidence map, the 16-Right longwall panel did not directly undermine the Walcott, Hayden-Gore Pass, or Western Area Power Administration power lines; or Foidel Creek during the first-half of 2004. The data and frequency for the survey monuments along the UPRR are presented in the attached Table No. 1. Portions of Fish Creek were undermined by the 16-Right Panel during the first-half of 2004. The postmining survey of Fish Creek in areas underlain by the 16-Right gate-road or panel center were completed in August of 2004. The postmining subsidence profile for Fish Creek over Panel 16-Right and the premining subsidence profile for Fish Creek over Pane] 17-Right are submitted as one drawing with this First Half 2004-Subsidence Report. II. Structures: The only structure affected during the first-half of 2004 reporting period was the Union Pacific Railroad. Visual inspections of the Union Pacific Railroad by UPRR personnel were conducted from May 5, 2004 through June 10, 2004. Daily surveys and observations of the UPRR over Panel 16-Right were also performed by Twentymile Coal Company (TCC) personnel from May 4, 2004 through July 7, 2004. Follow-up reports on the survey data and observations were submitted to designated UPRR personnel on a daily basis. "Prehumping" of the railroad track with ballast was initiated in May 2004, prior to undermining and subsidence of the track in May and June 2004. Unexpected delays prevented the pre-humping from being fully complete before subsidence began. Three small kinks in the track were discovered and repaired without incident by UPRR personnel. Final re-leveling of the rail line to the postmining target level will be performed by the UPRR in early summer 2005, as needed. A follow-up survey will be performed at that time and a final report, reflecting final survey data, will be submitted to the UPRR. Structures remained essentially unaffected during the reporting period, with the exception of the predicted impacts to the Union Pacific Railroad and Fish Creek. No adverse impacts, i.e. imminent failure of structures, were evident with regard to these structures. No repair work, beyond the minor realignment noted above, was required to the Union Pacific Railroad to address subsidence resulting from TCC's mining activities. 2004_ls[I-IalfSubReport.doc Page 1 of 3 09/13/04