Contamination from Uranium Tailings Ponds In one study of the ground water beneath two unlined uranium tailings ponds in Utah, a comparison was made of baseline natural uranium activity before the...

Contamination from Uranium Tailings Ponds

In one study of the ground water beneath two unlined uranium tailings ponds in Utah, a comparison was made of baseline natural uranium activity before the tailings ponds were put into service and the natural uranium activity after 11 y of operation (White & Gainer 1985). The tailings ponds, each of which covers about 40 ac, were constructed by placing earthen dams across a small valley. The surface geology is a fine-grained sandstone interfingered with siltstones and claystones. Ground-water flow is fracture controlled. Figure 22Ashows the locations of the tailings ponds and the fracture patterns affecting the ground water. Figure 22B shows the potentiometric surface. It was found that the baseline water quality showed somewhat elevated levels of natural uranium activity due to natural leaching of uranium-bearing rocks by water moving along a fracture system. Figure 22C shows the baseline natural uranium activity. It follows a linear pattern along the strike of a major fracture southwest of the lower tailings pond. After 11 y of operation, the natural uranium activity had increased significantly above the base

line measurements. Figure 22D shows the elevated activity, corrected for the baseline variation. The plume is spreading to the northwest, following the strike of the fractures. This illustrates one of the facets of ground-water contamination in fractured rock aquifers that are anisotropic. That is, the plume will tend to follow the fractures and not necessarily move normal to the potentiometric surface. If the aquifer were isotropic, from the potentiometric surface map one would expect that the plume would spread primarily to the southwest.