What a DUMP! - landfills across the U.S. are crammed full

Science World, April 9, 2001 by Mona Chiang

The garbage in your room is out of control. And burying your mess under layers of clothes is no longer a disguise--the heap is too big to ignore. So you start another pile in your sister's room. Guess what? Sounds like a U.S. landfill.

Last year, Americans generated nearly 390 million tons of trash--and more than half was carted off for landfill burial. Almost 100 landfills across the U.S. closed last year because they were crammed to the brim. And within 50 years, the approximately 2,216 landfills that exist today will reach full capacity.

DRY TOMBS

Contrary to popular belief, a landfill isn't a giant pit where trash is randomly dumped, buried, and left to rot. "Most U.S. landfills are called dry tombs," says Steve Wall of the U.S. Environmental Protection Agency (EPA). "Ideally, landfills are carefully engineered and monitored systems that keep household garbage dry so they don't contaminate surrounding water or air." (See diagram.)

A landfill has many protective layers:

1. Heavy machinery, like tractors and bulldozers, mashes one day's worth of garbage into tight blocks called cells. At the end of the day, a tractor smears a 6-inch layer of soil over the blocks and then further compacts lifts (adjoining rows and layers of cells).

2. About 6 inches of soil acts as a second barrier.

3. A rockier layer of soil holds back garbage chunks.

4. A fabric mat keeps soil layers from falling through.

5. Small rocks in a gravel layer filter particles from leachate.

6. Another fabric mat keeps gravel from piercing the lower layers.

7. Like a giant plastic garbage bag, a liner covers the entire bottom of the landfill to prevent trash and leachate from contacting outside soil. Leachate runs down the liner to a collection pipe.

8. In case the liner tears, a base of compacted clay acts as the landfill's "bulletproof vest." Clay is groundwater's last line of defense against seeping and leaking.

9. Like a sink drain, a collection pipe sits in the lowest portion of the landfill to drain out leachate.

10. Pumps pipe leachate from the landfill to a holding pond, where it stays until trucks carry the toxic liquid to a waste-water treatment facility.

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Every day, after landfill trash is compacted, it's smothered with a thick soil coveting, explains Wall. Compacted garbage sits atop multiple layers that drain out leachate (LEECH-ate), or toxic liquid waste. Leachate is then routed to a collection pond so that no liquid waste can trickle down to contaminate groundwater (water that can wind up in your tap). "Since the trash doesn't get enough liquid or oxygen," says Wall, "microorganisms that decompose waste work slower. The garbage inside could last for 30, 50, even 100 years."

When a landfill is full, it's "capped" with high-density polyethylene (a plastic material), a thick layer of earth, and planted with grass. Then state officials monitor the landfill for safety for a minimum of 30 years. But what happens afterward? "That's a good question," says Wall. "People are concerned because trash inside lasts for generations."

The EPA is continuously striving to perfect methods that will make landfills more efficient and safe. In the meantime, the EPA's critical message to Americans: Reduce, Reuse, and Recycle.

Did You Know?

* Landfills produce significant amounts of methane gas, which must be vented or collected. Most captured methane is burned off--but 123 landfills use the gas to generate power.

* When some old landfills have been excavated, 40-year-old newspapers have been found with readable print!

* Americans use over 65 billion aluminum soda cans each year--that's 1,500 cans for each person!

Cross-Curricular Connections

History: Choose a topic and research: When did commercially canned and frozen foods become popular? When were plastics invented? What was the biggest pollution problem in 1900?

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National Science Education Standards

Grades 5-8: properties and changes of properties in matter * abilities of technological design * science and technology in society

Grades 9-12: environmental quality * science and technology in local, national, and global challenges * abilities of technological design

Resources

Check with the Environmental Protection Agency for more on landfills:

www.epa.gov/epaoswer/non-hw/muncpl/disposal.htm

For more on how landfills work, log on to:

www.howstuffworks.com/landfill.htm

"Landfill to Living Room: Salvaged Building Materials are Catching On," E Magazine, March/April 2001, p. 44

Directions: After reading "What a Dump!," underline the correct answer to complete the sentence.

1. Last year, Americans generated (3.9; 39; 390) million tons of trash.

2. There are approximately (127; 1,106; 2,216) landfills operating in the U.S. today.

3. When a landfill is full, it's (melted down with chemicals, burned, capped).

4. After a landfill is shut down, it is monitored for at least (a year, 10 years, 30 years).

5. Garbage in landfills is compacted and placed in compartments called (boxes, cells, caves).