Closing an Open Dumpsite and Shifting - International ...

abandonment of the affected groundwater wells. Figure 1 shows how contaminated water
from a waste disposal facility contaminate surface waters and groundwater.
The composition of leachate depends on the stage of degradation and the type of wastes
within the disposal facility. In the first few years, leachate contain readily biodegradable
organic matter, resulting in an acidic pH and high biochemical oxygen demand (BOD5). With
time, leachate become simple dissolved organics and decrease in strength.
B.2 Gases
The decomposition of the waste also brings about the generation of gases, mainly methane
(about 50-65%) and carbon dioxide (about 35-45%). As methane is formed, it builds up
pressure and then begins to move through the soil, following the path of least resistance.
Often it moves sideways for a time before breaking through to the surface of the ground.
Methane is lighter than air and is highly flammable. If it enters a closed building and the
concentration builds up to about 5 to 15% in the air, a spark or a flame is likely to cause a
serious explosion.
Aside from being a flammable gas, methane released to the atmosphere greatly contributes to
the depletion of the ozone layer since it has approximately 15 to 20 times the global warming
potential of carbon dioxide.
B.3 Other impacts
Aside from the generation of leachate and methane gas, the exposed waste in open dumps can
become a breeding ground for vermin, flies, and other potential carriers of communicable
diseases. Open dumpsites without daily soil cover can also be a source of odor, dust and litter.
If open burning of solid waste is practiced (usually, to reduce volume), it could result in the
emission of toxic substances to the air from the burning of plastics and other materials. The
toxic fumes can cause chronic respiratory and other diseases, and it will increase the
concentration of air pollutants such as nitrogen oxides (NOx), sulfur oxides (SOx), heavy
metals (mercury, lead, chromium, cadmium, etc.), dioxins and furans, and particulate matter.
Open dumpsites also reduce property value, not only of the dumpsite area itself, but also the
properties adjacent to or near the disposal area due to the factors listed above as well as visual
degradation.
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