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A sanitary landfill is a pit with a protected bottom where trash is buried in layers, compacted (pressed down to make it more solid), and covered. A sanitary landfill can reduce harm from waste that has collected, and is safer than an open dumping site. But even the best sanitary landfill will fill up and, after many years, probably start to leak. To solve our waste problems, we still need to prevent waste in the first place.
It is difficult to turn open dumps into sanitary landfills. Instead, a community can build a new sanitary landfill and clean up the old site by transporting trash to the new one. A sanitary landfill protects community health when:
- it is built away from where people live.
- it is covered to prevent insects and other disease-carrying animals from breeding.
- it has a lining of hard-packed clay soil or plastic to prevent chemicals and germs from contaminating groundwater.
Because building and maintaining a sanitary landfill is a lot of work, it usually needs to be done in partnership with the community, local government, and other organizations, such as churches or businesses.
A landfill protects community health only if it is well managed. Good management includes training and support for landfill workers, and working together with resource recovery centers, toxic waste collectors, and local government.
Selecting a site
The first step in planning a landfill is choosing a site. In most places, the government requires a site assessment (a close look at the conditions of the site) before construction. This means a study of the type of soil and rocks, the kinds of plants that grow there, the distance from water sources and homes, and being sure that it is not a flood zone. For health and safety, a landfill site should be at least:
- 150 meters from coastal waters.
- 250 meters from fresh water, such as streams, ponds or swamps.
- 250 meters from protected forests.
- 500 meters from homes, and from wells or other drinking water.
- 500 meters from earthquake fault lines.
The bottom of the pit must be at least 2 meters above the highest groundwater level.
Making the landfill
The size of the landfill pit depends on the amount of trash that will go into it. All pits should be narrower at the bottom than the top to prevent them from collapsing. This shape also helps compact the trash because there is more weight on top than on the bottom.
A sign posted by the landfill gate with the hours it is open helps landfill workers better control what is dumped, and when, and how.
A well-built and well equipped landfill
such as sand, soil, or a water source
The lining has 3 layers:
Lining the pit
To protect groundwater, the landfill needs a protective lining at the bottom. A good lining can be made by compacting layers of clay, gravel, and soil. Building the landfill in an area with hard clay soil will make this easier.
If there are resources to provide a better protective lining, layers of thick plastic sheeting and thick fabric will give more protection, and a system of pipes and pumps can be built to remove liquids.
Filling the landfill
The way you fill a landfill depends on the amount of trash, how much time people have to do the work, and the local climate.
In places with high rainfall and little trash, such as towns that practice zero waste, each week or month you can dig a new hole lined with clay and gravel (in thinner layers than a larger landfill would need). Someone takes responsibility for bringing trash, filling the hole, compacting the trash, and covering it with soil. Burying trash little by little prevents water from collecting in the pits.
For a community with a large trash load, it is easiest to dig a large pit. Landfill workers add waste to the pit as it is brought in. Each time waste is added it is pressed down to make an even layer, then covered with large leaves (such as palm, banana, or palmetto) and a layer of soil, or soil, ash, and sand. This will prevent bad smells and stop insects from breeding. Making a large roof over the pit will keep rain out.
Capping the landfill
When the pit is full it should be capped with a layer of soil at least 90 cm deep. Wildflowers or grasses can be planted over it, but not plants that will be eaten, such as vegetables or fruit trees. Until the landfill is completely covered by plant life, it is best to keep grazing animals away.
|After it has been completely covered over, a well-managed|
landfill may become a green and pleasant area.
Difficulties with sanitary landfills
A pit where trash is dumped and then covered with soil can be maintained safely with few problems. But it can develop problems if liquid waste and gas (methane) collect in the pit.
Liquid waste (leachate)
If rainwater soaks into the landfill, it creates bad-smelling liquid waste that can carry poisons from trash into the groundwater. This is why it is important to line the landfill well and not to make it near a river, stream, or lake.
The best way to prevent leachate is to keep the landfill covered with a roof, or a canvas or plastic cover, until it is capped.
In landfills containing mixed waste, bacteria can grow and create methane gas. Methane can explode or catch fire if not managed carefully, and it adds to global warming. In many places, methane from landfills is captured and used to generate electricity. If you have no resources to do this, the best thing to do with methane is to provide vents for it to escape.
|Gas vents in a landfill|
A simple vent consists of a chimney made of small rocks held in a circular or square shape by a wire mesh, or you can use 200-liter drums with the bottoms removed. The height of the vent is raised as the height of the landfill increases. The number of vents needed depends on the size of the pit and the type of trash in the landfill.
A landfill that has been capped and has grass or plants growing on it may still release methane. If there are patches of dead grass, particularly if they are shaped like a circle, this is a sign that methane is escaping from the landfill. Place signs and warn people to stay at least 10 meters away from the area, because an explosion could be caused accidentally. Trained professionals should examine the landfill to decide how best to prevent an explosion.