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~, -~ $~ p~~EO ~2/~1~3 WFC SUBMITTAL 4 EFFECTS OF CAPILLARY RISE IN COAL PROCESSING WASTE DUMP (CIRUELA CANYON) The following computations are intended to examine the potential effect of capillary rise of waters in the gravel materials into the overlying waste dump. The approach was to estimate the height of capillary rise into the waste material, assuming that the water table in the gravel is positioned at the interface between the gravel and the waste material. By this means the volume of water potentially affected by contact with the waste is estimated. It is further assumed that this volume is entirely drained once the water table recedes, and that this cycle occurs once annually. It can be demonstrated by experiment and by theoretical calculations that drainage of a fine grained material overlying a coarse grained material is greatly impeded by this presence of the coarse material. Therefore, the assumption that complete drainage occurs is highly biased toward a worst case estimate. No measurements of the height of the capillary fringe in the waste material are available. Therefore, the height is estiamted from the equation ('McWhorter and Nelson, 1978)*; hd = 9.66 (K/n)-0.401 where: hd =height of capillary fringe; cm K =permeability, cm/s n =porosity, dimensionsless fraction A reasonable estimate for the permeability of the waste material (s 5x10-4 cm/s and the porosity is expected to be near 0.4. These values yield hd = 9.66 (5x10-4)-0.401 = 140 cm = 4.6 ft The area of contact between the waste material and the gravel is taken to be 10 acres. Thus, the volume of capillary water contacting the water is Volume=lOx4.6x0.4= 18.4 ac-ft The next step was to calculate the change in water quality in the Purgatoire River as a result of addition of 18.4 ac-ft of water with a degraded quality. This was accomplished with means of the mass balance. CaQ=QCb+QwCw or QC=Ca-Cb=CwQw/Q