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<br /> <br />i <br />(19) 'i i <br />Ii <br />It is worth noting here, as noted in the plan, that Maximum <br />economic recovery of the coal requires retreat mining im paneLs <br />and removal of pillars and submains. This will result in collapse <br />of the mine workings underground. What cannot be determiyied in <br />advance is the surface impact of this underground collaps <br />will make every effox-t to monitor any surface impacts so <br />the USGS may balance the need for maximum economic recove <br />CWI <br />hat <br />with <br />the need to develop the design measures to control subsidence. <br />i <br />CWI is not in a position to determine ho~a to improve its (design <br />techniques until subsidence monitoring provides additional <br />information. <br />CWI is aware that B seam mininP in the Somerset mine Several <br />miles east of the Orchard Valley Mine has resulted in surface <br />subsidence. Experience from mining in that area is not!t~ecessarily <br />revelant because conditions can not be presumed to be id~IIntical. <br />It may be more likely that subsidence will occur as a ries~ult of <br />CWI's D seam mining, which is closer to the surface tha~n~the B seam <br />mining at tha Somerset ?'.i.-.a, but this is by no means cgrtain. <br />i <br />i <br />,,null l•n ~•~. 1lli li I n:~, ',i Il~nlni I,nin :nil lul rl Iw li,•~•,nla1 [3 <br />----r <br />'-• - ~",,~-. ,,...~., :un~ud ~~~uural Yerforu,.Inc~ Standards. <br />ram <br />~ ; <br />i <br />~J ~~ ~' I~t ~IlA ~~ Y~II tl <br />