The Basics of Landfills

Landfill Basics -- How They are Constructed and Why They Fail

Questions to Ask About Landfills

Other Resources on Landfills

 Landfill Articles
  • Leaky Liners & Leachate
  • Hazardous Waste & Environmental Racism
  • Superfund & Health
  • Landfill Politics
  • Strategies & Alternatives

    Primer on Landfill Gas as "Green" Energy

    • WHAT IS A LANDFILL?

    A secure landfill is a carefully engineered depression in the ground (or built on top of the ground, resembling a football stadium) into which wastes are put. The aim is to avoid any hydraulic [water-related] connection between the wastes and the surrounding environment, particularly groundwater. Basically, a landfill is a bathtub in the ground; a double-lined landfill is one bathtub inside another. Bathtubs leak two ways: out the bottom or over the top.

    WHAT IS THE COMPOSITION OF A LANDFILL?

    There are four critical elements in a secure landfill: a bottom liner, a leachate collection system, a cover, and the natural hydrogeologic setting. The natural setting can be selected to minimize the possibility of wastes escaping to groundwater beneath a landfill. The three other elements must be engineered. Each of these elements is critical to success.

    THE NATURAL HYDROGEOLOGIC SETTING:

    You want the geology to do two contradictory things for you. To prevent the wastes from escaping, you want rocks as tight (waterproof) as possible. Yet if leakage occurs, you want the geology to be as simple as possible so you can easily predict where the wastes will go. Then you can put down wells and capture the escaped wastes by pumping. Fractured bedrock is highly undesirable beneath a landfill because the wastes cannot be located if they escape. Mines and quarries should be avoided because they frequently contact the groundwater.

    WHAT IS A BOTTOM LINER?

    It may be one or more layers of clay or a synthetic flexible membrane (or a combination of these). The liner effectively creates a bathtub in the ground. If the bottom liner fails, wastes will migrate directly into the environment. There are three types of liners: clay, plastic, and composite.

    WHAT IS WRONG WITH A CLAY LINER?

    Natural clay is often fractured and cracked. A mechanism called diffusion will move organic chemicals like benzene through a three-foot thick clay landfill liner in approximately five years. Some chemicals can degrade clay.

    WHAT IS WRONG WITH A PLASTIC LINER?

    The very best landfill liners today are made of a tough plastic film called high density polyethylene (HDPE). A number of household chemicals will degrade HDPE, permeating it (passing though it), making it lose its strength, softening it, or making it become brittle and crack. Not only will household chemicals, such as moth balls, degrade HDPE, but much more benign things can cause it to develop stress cracks, such as, margarine, vinegar, ethyl alcohol (booze), shoe polish, peppermint oil, to name a few.

    WHAT IS WRONG WITH COMPOSITE LINERS?

    A Composite liner is a single liner made of two parts, a plastic liner and compacted soil (usually clay soil). Reports show that all plastic liners (also called Flexible Membrane Liners, or FMLs) will have some leaks. It is important to realize that all materials used as liners are at least slightly permeable to liquids or gases and a certain amount of permeation through liners should be expected. Additional leakage results from defects such as cracks, holes, and faulty seams. Studies show that a 10-acre landfill will have a leak rate somewhere between 0.2 and 10 gallons per day.

    WHAT IS A LEACHATE COLLECTION SYSTEM?

    Leachate is water that gets badly contaminated by contacting wastes. It seeps to the bottom of a landfill and is collected by a system of pipes. The bottom of the landfill is sloped; pipes laid along the bottom capture contaminated water and other fluid (leachate) as they accumulate. The pumped leachate is treated at a wastewater treatment plant (and the solids removed from the leachate during this step are returned to the landfill, or are sent to some other landfill). If leachate collection pipes clog up and leachate remains in the landfill, fluids can build up in the bathtub. The resulting liquid pressure becomes the main force driving waste out the bottom of the landfill when the bottom liner fails.

    WHAT ARE SOME OF THE PROBLEMS WITH LEACHATE COLLECTION SYSTEMS?

    Leachate collection systems can clog up in less than a decade. They fail in several known ways:
    1. they clog up from silt or mud;
    2. they can clog up because of growth of microorganisms in the pipes;
    3. they can clog up because of a chemical reaction leading to the precipitation of minerals in the pipes; or
    4. the pipes become weakened by chemical attack (acids, solvents, oxidizing agents, or corrosion) and may then be crushed by the tons of garbage piled on them.

    WHAT IS A COVER?

    A cover or cap is an umbrella over the landfill to keep water out (to prevent leachate formation). It will generally consist of several sloped layers: clay or membrane liner (to prevent rain from intruding), overlain by a very permeable layer of sandy or gravelly soil (to promote rain runoff), overlain by topsoil in which vegetation can root (to stabilize the underlying layers of the cover). If the cover (cap) is not maintained, rain will enter the landfill resulting in buildup of leachate to the point where the bathtub overflows its sides and wastes enter the environment.

    WHAT ARE THE PROBLEMS WITH COVERS?

    Covers are vulnerable to attack from at least seven sources:
    1. Erosion by natural weathering (rain, hail, snow, freeze-thaw cycles, and wind)
    2. Vegetation, such as shrubs and trees that continually compete with grasses for available space, sending down roots that will relentlessly seek to penetrate the cover;
    3. Burrowing or soil- dwelling mammals (woodchucks, mice, moles, voles), reptiles (snakes, tortoises), insects (ants, beetles), and worms will present constant threats to the integrity of the cover;
    4. Sunlight (if any of these other natural agents should succeed in uncovering a portion of the umbrella) will dry out clay (permitting cracks to develop), or destroy membrane liners through the action of ultraviolet radiation;
    5. Subsidence--an uneven cave-in of the cap caused by settling of wastes or organic decay of wastes, or by loss of liquids from landfilled drums--can result in cracks in clay or tears in membrane liners, or result in ponding on the surface, which can make a clay cap mushy or can subject the cap to freeze-thaw pressures;
    6. Rubber tires, which "float" upward in a landfill; and
    7. Human activities of many kinds.

    Prepared by:

    Environmental Research Foundation
    P.O. Box 5036
    Annapolis, MD 21403-7036
    phone (410) 263-1584
    fax (410) 263-8944

    Environmental Research Foundation's
    RACHEL's Environment & Health Weekly Articles

    Leaky Liners & Leachate

    #90Municipal Dump Leachate Is As Toxic As That From Hazardous Waste Dumps
    #119Leachate Collection Systems: The Achilles' Heel Of Landfills
    #37EPA Says All Landfills Leak, Even Those Using Best Available Liners
    #71Decade-Old Study Revealed the Polluting Effects of Landfills
    #116Why All Landfills Leak
    #117The Best Landfill Liner: HDPE
    #125Clay Landfill Liners Leak In Ways That Surprise Landfill Designers
    #216Some Hidden Hazards Of A Plastic World [Plastics Aren't Biodegradable]
    #217Why Plastic Landfill Liners Always Fail
    #316New Evidence That All Landfills Leak
    #109Catch-22s of Landfill Design
    #177Unrecognized Cause of Landfill Failures
    #226Toxic Gases Emitted From Landfills

    Hazardous Waste & Environmental Racism

    #162Fine Particles--Part 5: Incineration Worsens Landfill Hazards
    #164The Landfiller's New Plan: Megafills
    #180Commercial Hazardous Waste Landfills
    #182Chemical Dumps Make Good Homes For Poor Families, EPA indicates
    #190Incinerator Ash--Part 2: All Wastes Must Go Somewhere Forever
    #403EDF Proposes Incinerator Ash Dumps
    #224Nation's Greatest Danger: Secrecy [Military Toxics]
    #227The Military Toxics Scandal Deepens
    #239The Poisoners Invade Indian Country
    #272Government Facts on Dumps Remain Sketchy
    #278Government Burial Of Asbestos On Sacred Navajo Land
    #183Coming Your Way: Radioactive Garbage

    Superfund & Health

    #176Hooked on Danger: Expanding Solid Waste Landfills
    #271National Academy Superfund Dumps Make People Sick
    #332Why Exalt Wise Use? [industry can't stop polluting]
    #370Superfund Dumps & Health, Part 2
    #371Superfund Dumps & Health, Part 3

    Landfill Politics

    #231EPA Proposes A Perfect Solution For New Municipal Solid Waste Landfills
    #238The Regulatory-Industrial Complex
    #241Citizens Seek Reform Of The Nation's Hazardous Waste Law
    #268EPA's New Landfill Rules Protect Big Garbage Haulers
    #288New Tools For Citizens: 'Bad Boy' Laws
    #292Congress Creates A Monster: The ATSDR [superfund]

    Strategies & Alternatives

    #232Public Ownership Of Dumps Is The Key
    #260Storing Superfund Waste In Concrete Buildings Seems to Make Sense
    #289Good Solid Waste Alternatives [composting]
    #307New Garbage Strategies Are Now Possible
    #352Composting Municipal Solid Waste

    Environmental Research Foundation's
    QUESTIONS TO ASK ABOUT LANDFILLS

    It is important to have a basic understanding of the landfill being proposed for your community. We suggest that you ask the following questions of both the landfill operator and the local governing boards that will be giving the permits to the landfill operator.

  • How big will the landfill be in acres?

  • What is the depth of the landfill in feet, and what will be the height of the highest point of the cap after the landfill is closed?

  • How much of the acreage will be filled with garbage?

  • How much of the acreage will be used for the buffer zone?

  • How much of the acreage will be unused?

  • What is the maximum tons per day they will accept?

  • Does the contract have a minimum tons per day quota (often called put or pay clauses)? If it does who is responsible for finding the additional tonnage or the money in lieu of the tonnage?

  • What type of garbage will it be filled with:

    municipal solid waste
    medical waste
    hazardous waste
    low level radioactive waste
    below regulatory concern (brc) waste
    special waste (often incinerator ash)
    incinerator ash
    industrial solid waste
    demolition debris
    other waste

  • Will they be putting recyclables in the landfill (glass, aluminum, tin, paper, etc.)?

  • Will they be putting clean organic compostables in the landfill (for example, yard wastes)?

  • If they are putting recyclables and organic compostables in the landfill will they be putting them in separate cells?

  • In tons per day, how much of the garbage will come from your town, county, state, out-of-state?

  • How many years will the landfill be in operation?

  • Will it be lined and capped? If so what will these be made of?

  • How long will the operators be responsible for it once it is closed, often referred to as the post-closure period?

  • Who will be responsible for it once the post-closure period is over?

    RESOURCES ON LANDFILLS

    ORGANIZATIONS AND JOURNALS:

    Center for Health, Environment & Justice
    P.O. Box 6806
    Falls Church, VA 22040
    (703) 237-CCHW
    Publishes bimonthly: EVERYONE'S BACKYARD

    G. Fred Lee and Associates
    27298 East El Macero Drive
    El Macero, CA 95618
    (530) 753-9630
    www.gfredlee.com

    Greenpeace
    1436 U Street, N.W.
    Washington, DC 20009
    (202) 462-1177
    Publishes quarterly: GREENPEACE
    www.greenpeace.org

    PAHLS (People Against Hazardous Landfill Sites)
    Suite A
    102 North Morgan
    Valparaiso, IN 46383
    (219) 465-7466

    Southwest Research and Information Center
    P.O. Box 4524
    Albuquerque, NM 87106
    (505) 262-1862
    Publishes quarterly: THE WORKBOOK

    SUGGESTED READING:

    Citizen's Clearinghouse for Hazardous Wastes. LAND DISPOSAL ... THE DINOSAUR OF DISPOSAL METHODS. Falls Church, Va.: Citizen's Clearinghouse for Hazardous Wastes, April 1986.

    Connett, Paul. WASTE MANAGEMENT: AS IF THE FUTURE MATTERED. Canton, N.Y.: Work on Waste USA, May 1988.

    Cozza, Blythe I. DEBUNKING THE LANDFILL HIGH TECHNOLOGY MYTH. Wheeler, Ind.: PAHLS, Inc., 1989.

    Lee, G. Fred and Anne R. Jones. MUNICIPAL SOLID WASTE MANAGEMENT IN LINED, "DRY TOMB" LANDFILLS: A TECHNOLOGICALLY FLAWED APPROACH FOR PROTECTION OF GROUNDWATER QUALITY. El Macero, Calif.: G. Fred Lee & Associates, March, 1992.

    VIDEOS:

    Greenpeace. WHY ALL LANDFILLS LEAK [this video features our very own Peter Montague explaining in detail everything you need to know about landfills]. Washington, D.C.: Greenpeace [Public Information; phone: (202) 319-2444], 1991.

    Compiled by Maria B. Pellerano, revised by Brady Parkhurst, edited by Andrea K. Fearneyhough. March 1995.

    Other Landfill Resources:

    This site is maintained by the ACTION Center.

    Last modified: 26 March 2003

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