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Memo to Janet Binns <br />Twenty Mile Coal Company 1998 Subsidence Reports <br />page 3 <br />average depth of 3 feet, based on the very limited small-scale graphic profile <br />presented, these four ponds may now hold approximately 15 acre-feet of water. <br />No discussion is provided within the brief text of these subsidence reports <br />regarding this surface hydrology detail. This could be a significant topic of <br />interest. I assume that an appropriate discussion of this topic is being provided <br />by TMC within their Annual Hydrology Report. I further assume that TMC is <br />providing satisfactory discussions of topics such as; were these ponds formed <br />solely by subsidence troughing?; will they subsequently be breached by natural <br />phenomena or artificially eliminated? These topics should be thoroughly <br />described somewher~ hin the various monitoring reports provided by Twenty <br />Mile Coal Company. <br />Finally, the semi-annually revised version of the "Subsidence Map" contained <br />within the 1998 Second Half Subsidence Report, depicts (for the first time) two <br />"Residences" and 1 "Barn" above Panel 5 Right. Assuming TMC's recent <br />impressive rate of longwall face advance, it appears these structures should be <br />undermined during the next few months. No subsidence data has been presented <br />regarding any of these structures. They must be monumented and surveyed prior <br />to face approach within the potential angle of draw influence. In fact, since <br />two of these structures are in close horizontal proximity to previously <br />excavated gateroads, they should already have been monumented and surveyed, <br />in order to establish their baseline pre-subsidence location and elevation. The <br />Division needs to assure that TMC has accomplished this structure <br />monumentation and baseline data collection. <br />_~ <br />Cc: Dan Hernandez <br />Doc: M:\COAL\JAP\TMCSU698.WPD <br />JP/JP <br />