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ArrHeDU a SPHCIFIC BHSHHTIOH AHD ITS COHSHQ~BHCHS TO WAiHB HOY@BHi IH SHH AHHA OF THH SODTBFISLD HIPS Specific retention of a soil or rock is the ratio of the volume of water retained after saturating and then draining by gravity, to its own volume. The water retained in the material ie held by capillary forces against the pull of gravity. Before a coal seam such as the Red Arrow or Dirty Jack O'Lantern in the Vermejo Formation ie mined. all pore spaces are filled with eater. except for possibly a minimal amount of entrapped air. When underground excavation of the coal begins, valet is alloyed to drain freely into the resultant mine cavity (see Figures 5 and 6 in teat). That eater which remains in the formation. above the mine floor level. is specific retention. Similarly. any water left within lumps of removed coal is specific retention. After excavation of a coal seam has started, the aquifer is permanently altered. The saturated level of the aquifer is lowered to the floor level of the mine. or to the free water level in the mine if the mine is flooded. Coal removed from the face of the mine is above the saturated level and any water left in the mined coal is specific retention. Water removed with the raw coal from the Southfield Mine, specific retentionl -estimated to be 8.33 percent by wet weight of the raw coal - ie ~mined^ water. or water which is not an active part of the surface 1. A laboratory estimate of specific retention is obtained by placing a thoroughly wetted core sample of coal in a desiccator for one day with 97 percent relative humidity and 30 pounds of vacuum preesure.o The moist weight is then recorded, and the sample ie oven dried at 104 C for four days. The difference between the moist weight and the oven-dried weight is an estimate of the amount of water which would not drain by the force of gravity alone.