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eFpaaDiz a sracl3nc esr~rrioa ~ l:s coassQu~cas To vsrg aov~r n Tan seas of rHa soDr~isla Musa Specific retention of a soil or rock i.s the ratio of the volume o~ eater retained after saturating sad then draining by gravity. to its a ow wlame. The rater retained is the material ie held by capillary `forces against the poll of gravity. Eefore a coal seam such as the Bed Arror or Dirty Jaek O~Lantern _~n the verrtejo Formstion is mined. all pore spaces are filled with rater. e-ezcept for possibly a minimal aswunt of entrapped air. tdhen a~er~groand excavation of [be coal begins. rater i.s alloyed to drain freely unto the reealtant mine cavity (see Figures 5 and 6 in text). That rater - rhieh I remains in the formation. above the mine floor level. is smmeeifie retention. Similarly. any rater left rithin lumps of removed cxoal is specific retention. After excavation of a coal seam has started. the aquifer is permanently I altered. The saturated level of the aquifer is lore red to the floor= level of the mine. or to the free rater level in the mine if the urine is flooded. Coal removed from the face of the mine ie above the sarzznrated level and any rater left in the mined coal is specific retention. Rater removed rich the ray coal from the Southfield !line. epspecific retention) -estimated to be 8.33 percent by wet refight of the ray c coal - 7 is ~mined~ rater, or rater which is not an active part of the smarfaee J 1._ A laboratory estimate of specific retention is obtained by pIarscing a I thoroughly vetted core sample of coal in a desiccator for one day v~ith 97 percent relative huaidity and 30 pounds of vacuum preseure.~ They moist refight is then recorded. and the eaaple is oven dried at 104 C _'ar four days. The difference betreen the moist refight and the oven-dried refight I is an estimate of the amount of rater rhich rould not drain by tie=s force of gravity alone.