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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 3. (March)

First Page: 570

Last Page: 570

Title: Unsaturated Flow Conditions Beneath Lined Tailings Disposal Ponds: ABSTRACT

Author(s): Daniel B. Stephens, Joel Siegel

Article Type: Meeting abstract


The uranium milling industry may soon dispose of substantial volumes of liquid waste in lined evaporation ponds. The potential for seepage through the low-permeable liner to contaminate ground water can only be assessed by analytic and numeric models. These models predict that, prior to reaching the water table, the liquid phase of the flow region will be unsaturated, except where perching may occur just above very low-permeable strata. None of the models actually simulate the effects of fractures in consolidated sediments.

Because seepage beneath the pond is predicted to occur under partly saturated conditions, piezometers usually employed in ground-water studies generally will not be effective monitoring tools. However, neutron moisture probes, suction lysimeters, and tensiometers well known to soil physicists could be used to monitor unsaturated flow. Unfortunately, none of these instruments is likely to be highly reliable in fractured-rock environments or in heterogeneous sound rock with a limited number of monitoring points. In fractured and nonfractured rock the primary means of detecting seepage losses exceeding model predictions should be from a mass balance of inflow rate minus evaporation.

Owing to unsaturated conditions beneath the pond, a well completed within the seepage zone could not produce water. This satisfies the NMEID mandate to protect future groundwater users after operations cease unless the seepage fluids contaminate the regional aquifer. Two- and three-dimensional numeric models show that seepage spreads beyond the perimeter of the pond; this may not be compatible with USEPA solid-waste-management regulations.

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Copyright 1997 American Association of Petroleum Geologists