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.~-~~~ ,y. ~~.v~ m~rvi v~~ rvi.., Q711 Q90 51'7, Sp(~-71-Oq A'.id dld~ oa7p 5"1 <br />5tr-CU-~tf BUR Iy~Jtl John F Abrl Jr r"AX N0. 303278&183 P. p4 <br />°11^ 9aam/boar Creek Inp~ct Page d September 11, 199A <br />maximum planned 12-foot "D" Seam mining height. Penq's prediction <br />is based on a field method chat quanCiflea the water loss Curing <br />drilling. Any water_oss in exceea o! 0.5 qpm per foot o! borehole <br />drilled downward toward a completed langwall panel is considered to <br />be in the Cractured rock zone. Peng lurther states that the water <br />`_os~ increases to 5 gpm per foot of bcrehols when the caved zone is <br />approached. Figure 4 presents lield data from the water loss <br />method Tor "Medium hard rock", delined as having worse conductivity <br />than "Hard and strong rock". The permeability of the alternatinv <br />sandstone and shale beds overlying the "D" Seam will ba relatively <br />poor vertically because of the shale beds. The lateral permeabil- <br />ity should be hlgh in the sandstone beds. <br />Peng provides Table 2 for predicting the fracture zone helght <br />for four claaaee of overburden rock. This table is based an "200 <br />boreholea in 27 mines". The predicted fracture zone height (lU) !or <br />"Bard and strong sock' ia: <br />hr' o.~sm•o•r ' a~K ~.a.a ' a~f ' 7~ foot for l2dhot mintng helght <br />for "Medium strong rock" is: - <br />~' o.ss: i•t ' ax:~•:•~ ~ ~ ' S 150et for 12-loot miring height <br />for "9oft and weak rock" is: <br />• hr' a.rm •~i.~ ' asrui • i.s ' ~ ' 29 feat fa 12-boot mining hdght <br />for "weathered salt and woak rock" is: <br />hr ~~;' :.XU]+t.~ ° ~' ]9 fiat for 12-foot mining height <br />TOTAIz THICKNESS OF REDUCED P14 i1i14.P,BILITY OVERLYING ROCK <br />Adding the most realistic 48-toot caved zone heightr four <br />times the maximum 12-foOt mining height to the zracture zone height <br />for even "Hard and atronq rock" results in the prediction that ro <br />water will be loat_lrom Hear Creek as long ae there is at least 121 <br />feet of rocK between the "D" Seem longwall panels and the bed of <br />Bear Creek. The approximate 400-foot of overburden between Bear <br />Creek and the "D" Seam workings will protect Bear Creek from water <br />loss even it the absolute worst-east pradlction for caved zone <br />he:yht of 96 feet is used, for a combined height of fractured and <br />caved zones of 169 feet. <br /> <br />