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SECOND-HALF 2006 SUBSIDENCE REPORT <br /> <br />I. Survey Data: <br />During the second-half of 2006, mining continued in the 19-Right I,ongwall Panel, which <br />lies beneath and parallel to two powerlines, owned by Western Area Power <br />Administration (WAPA) and Tri-State/Public Service Company of Colorado. A baseline <br />survey of the powerlines was completed by September 14, 2005, prior to initiation of <br />mining activities. Starting with initiation of mining in the 19-Right Panel in May (and <br />prior to undermining the powerlines), survey data has been collected daily for the bases of <br />each supporting powerpole as the longwall continues to mine east to west. Surveys of the <br />powerpole structures will continue until mining in the 19-Right Panel is completed. <br />Visual inspection of the structures will continue on a monthly basis for 3 months <br />following completion of mining. <br />II. Structures: <br />As noted above, starting in May 2006, mining in the 19-Right Panel has subsided two <br />powerlines from the eastern-most powerpole, 145-1. Twentymile Coal Company <br />personnel complete daily surveys of the powetpole structures, and will continue the <br />surveys and associated reporting to both the CDRMS and designated representatives for <br />• the powerline owners through completion of mining in the 19-Right Panel. In <br />conjunction with the powerline surveys, Twentymile Coal Company personnel also <br />conduct daily visual inspections of the subsided powerpole structures. <br />Structures remained essentially unaffected during the reporting period, with the exception <br />to predicted impacts to the powerlines over the 19-Right Longwall Panel. <br />III. Man: <br />Monitoring locations for the second-half of 2006 are shown on the Second-Half 2006, <br />Subsidence Map. The map also indicates the location of the longwall face on a monthly <br />basis and the projected subsidence limits where overlying creeks or structures may be <br />affected, based on mining depth and angle-of-draw. <br />IV. Vegetation Monitoring: <br />Vegetation monitoring (riparian survey) for the 16- and 17--Right Panels was last <br />performed during athree-day period from August 30, 2005 through September 1, 2005. <br />For the vegetation monitoring report, which evaluates any changes in riparian vegetation <br />conditions and characteristics for Fish Creek, relative to the measured baseline <br />conditions, please refer to the previous subsidence report. <br />• <br />2006_2ndHalfSubReport Page 1 oft 3/13/2006 <br />