Laserfiche WebLink
6 <br />In summary, average post -mining spoil permeabilities are estimated to be about <br />10-3 to 10-4 cm/sec. <br />The permeability coefficients of 15 cylinders containing fly ash, gypsum and time <br />were measured after curing for 28 days. These mixtures are the same ones as were <br />tested in the unconfined compressive strength tests. Three by six inch cylinders <br />were taken after curing for 28 days in a constant humidity room and placed in a <br />constant head permeameter similar to the one depicted in Figure 4.3-5. Water was <br />forced through the test specimens by applying a slight positive pressure water <br />head. The effluent volume was then measured as a function of time. The permea- <br />bility coefficient was then calculated from the water head, area, volume, height <br />and time by the following equation: <br />Permeability Coefficient (cm/sec) = <br />volume of water (cm3) x height (cm) <br />• time (sec) x water head (cm) x area (cm2) <br />The results obtained from these calculations are presented in Table 4.3-11. <br />The permeability coefficients ranged from 10-4 to 10-6 cm/sec. These <br />permeability coefficients are similar to those experienced with most scrubber <br />sludges, compacted bituminous fly ashes, and mixtures of bituminous fly ash and <br />scrubber sludges. Assuming saturation and a permeability coefficient of 10-5 <br />cm/sec, percolating water will move through the waste at a velocity of 10 feet <br />per year. Correspondingly, the permeablity coefficient of 10-6 is equivalent <br />to a percolation rate of 1 foot per year. <br />These permeability coefficients of the waste mixtures (10-4 to 10-6 <br />cm/sec) are 10 to 100 times less permeable than those of the overburden (10-3 <br />to 10-4 cm/sec) indicating that flow of water will preferentially move <br />through overburden instead of waste. <br />4-52 <br />