Closing an Open Dumpsite and Shifting - International ...

Settling can produce wide cracks in the cover of the disposal facility, exposing the wastes to
vermin, flies and stray animals. It also allows gas and odors to escape and water to infiltrate,
the latter causing increased settlement or even collapse of the waste mounds. Differential
settling can also cause depressions, which may result into the ponding of water. Figure 14
shows a closed disposal area prior to settlement, while Figure 15 shows the effects of
settlement and not maintaining proper grades.
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Figure 14. Before Settlement Figure 15. After Settlement
A.2 Bearing Capacity
Simply put, the bearing capacity of a completed disposal site is the measure of its ability to
support foundation. The bearing capacity of the cover material depends on the characteristics
of the underlying waste and the compaction achieved during operation and closure. To
construct substantial structures over an old disposal site generally requires deep footings to
assure a firm foundation.
In contrast to natural soils, which are not as heterogeneous as wastes and produce a
predictable pattern of deformation, solid wastes do not produce a uniform pattern of
deformation when subjected to stress (loads) but instead, continues to alter its structure and
composition over a long period of time. Thus, it is prudent that extreme caution be taken
when conducting bearing capacity tests of completed disposal sites in the hope that heavy
structures can be erected over it.
A.3 Gases
Gaseous by-products of decomposition will continue to be produced long after closure of the
disposal site. Methane can accumulate in confined areas, structures and cause explosions. It
can also kill or stunt the growth of vegetation. Consequently, structures over and nearby
should have ventilation and monitoring systems in their foundations to detect gas buildup.
A.4 Corrosion
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Because of the organic acids produced during waste decomposition, liquids from a completed
disposal site are very corrosive. Unprotected steel, underground pipes, structural foundations
and utility lines are subject to these corrosive elements. The acids can also deteriorate
concrete surfaces, and in the process, expose the reinforcing bars of the structure and cause
the concrete to fail. To mitigate these effects, all materials belowground at a closed disposal
site that have the potential to corrode should be protected from these deleterious effects.
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cracks water
ponding
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