31    EFFECTS OF ORGANIC FLUIDS ON CLAY PERMEABILITY
Frazier Parker, Jr., Associate Professor
Larry D. Benefield, Alumni Professor
Department of Civil Engineering
Auburn University
Auburn, Alabama 36849
Marshall M. Nelson, Engineer
Soil Conservation Service
U.S. Department of Agriculture
Auburn, Alabama 36830
INTRODUCTION
It has been estimated that there were over 41 million wet metric tons of hazardous wastes produced
in the U.S. during 1980. The single largest source is the chemical and allied products industry, which
accounts for 62% of all hazardous wastes produced. Approximately 83% of hazardous wastes are
treated or disposed in on-site facilities by the industry. The rest is transported to commercial off-site
facilities. Secure landfill and treatment are two options used for about 66% of these wastes. The
remaining wastes are incinerated, land treated, deep well injected, or recovered [1].
Secure landfills used for disposal of chemical wastes are commonly lined with several feet of
compacted clay to provide a supposedly impermeable barrier to assure that chemical wastes placed
into the landfills will not contaminate underlying groundwater. Recent research has shown that
reliance on the typical low permeability of compacted clay may be justified only if the permeant is
water. This research has shown that the impermeability of clay barriers can be permanently destroyed
thus destroying their function when exposed to various chemical permeants. Therefore, all chemical
materials proposed for disposal into clay-sealed landfills should be identified, and those which
adversely affect the impermeability of clay barriers should be disposed of in some other manner. The
major obstacle to the development of such a management procedure is the identification of chemicals
that adversely affect clay permeability and the identification of clays that may be resistant to degradation. Because permeability tests on clays require large amounts of time (up to a month), considerable
operator skill and specialized equipment [2], only a few organic fluids and clay soils have been
studied.
The objective of this study was to evaluate the consolidation test as a means of assessing the effects
of chemical permeants on clay permeability. Consolidation tests can be performed in approximately
one week, the required operator skill is not great and equipment is readily available. The use of the
consolidation test is not without distractions, however. Coefficients of permeability will not be precise
since the consolidation process depends on the stress-strain state and fluid equilibrium conditions in
the soil. Still, for comparative studies permeability values from consolidation tests may be as reliable
as other laboratory estimated values. For example, results from a recent study [3] showed actual
permeabilities of compacted clay liners as much as 1000 times greater than laboratory predicted
permeabilities. Recognizing that actual permeabilities are not likely to be obtained in the laboratory,
the consolidation tests become an attractive tool for delineating the effects of organic fluids on clay
permeability.
BACKGROUND
A secure landfill is a carefully-engineered depression in the ground for storage of hazardous wastes
[4,5]. A bottom liner is normally provided to prevent any hydraulic connection between the wastes
and the surrounding environment, particularly the ground water. In many cases the bottom liner is
composed of one or more layers of clay. However, synthetic membrane liners are now also required.
Clay liner permeabilities are typically determined as if pure water will be the leachate. In contrast,
the actual leachates generated in industrial landfills are most likely to be either highly contaminated
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