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Solid Waste Landfills
 

Solid Waste Landfills

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    Solid Waste Landfills Solid Waste Landfills Presentation Transcript

    • Solid Waste Landfills Robert B. Gilbert Assistant Professor of Civil Engineering The University of Texas at Austin
    • Background
      • More than 5,000 landfills in U.S.
      • More than 500 landfills in Texas
      • 75 % of Municipal Solid Waste (MSW) ends up in a landfill (120 million tons/year)
      • Landfills are an economical solution
        • $30/ton to landfill MSW (1992)
        • $52/ton for waste to energy of MSW (1992)
      • Products of treatment (e.g., incinerator ash) must be landfilled
      • Hence, landfills are not going away
    • Regulations
      • Specify what can and cannot be put into a landfill
      • Give design, construction and operation standards
      • Give environmental monitoring requirements
      • Drive the industry
      Investment ($) Profit ($) Permit
    • Regulations - History
      • Environmental Activism in 1960’s
      • National Environmental Policy Act (1970)
      • Clean Air Act (1970)
      • Clean Water Act (1972)
      • Resource Conservation and Recovery Act (1976)
        • Clean Air and Water Acts pushed waste to land
        • RCRA intended to close the loop
        • Defined waste as hazardous and non-hazardous
        • Initial focus was on hazardous waste
    • Love Canal - Background
      • William T. Love started a 7-mile long canal in 1890’s to harness power from Niagra Falls
      • Development of alternating current (which could be transmitted farther than direct current) made canal obsolete: only two 1/4-mile sections were excavated
      • AC power brought industry to area, particularly chemical companies
      • Hooker Chemical and Plastic Corp. manufactured plastics, chemicals and pesticides (chlorinated organic chemicals)
    • Love Canal - Background
      • 1930’s: Hooker began disposing waste in north section of canal
      • 1947: other chemical companies, the city of Niagra Falls, and the U.S. government were using the canal as a landfill
      • 1952: canal was closed and capped by Hooker
    • Love Canal - Plan View N Love Canal 1968 Expressway Niagra River Groundwater Flow A A’
    • Love Canal - Cross Section Canal Silt Clay Water Table Bedrock 0’ -10’ -40’ A A’
    • Love Canal - Problems
      • 1953: City of Niagra Falls ignores Hooker’s warnings and buys canal for a new grade school
      • 1955: 99th Street School completed on top of canal and homes built around perimeter
      • 1958: Children burned in puddle in playground
      • 1959: Oily sludge oozing into basement of house
      • 1968: Expressway built and problems increase
      • 1974: Residential pool uplifted by yellow, blue and orchid colored groundwater
      • 1975: Sink hole developed in playground
    • Love Canal - Response
      • 1975: City began investigating problems
        • toxic substances in basement air
        • high levels of benzene, chloroform and trichloroethene in groundwater
        • high rates of birth defects/miscarriages
      • City slow to react (Hooker employed 3,000 workers locally)
      • 1977: Local and regional news began reporting about problems
      • 8/2/78: Headline of New York Times about Love Canal; lead story on national television news
    • Love Canal - Resolution
      • 1978: 237 families relocated and school closed
      • 1980: 700 more houses evacuated
      • 1980’s: Hooker (now known as Occidental Chemical) and residents settled out of court for $30 million
      • 1980’s: New cap placed on canal
      • Today: People are moving back to the area
    • Love Canal - Questions
      • Who was responsible?
        • Hooker
        • City of Niagra Falls
        • State or Federal Government
        • Other Landfill Users
      • How many more Love Canals existed (ticking time bombs)?
        • Over 1,000 national sites identified
      • How can we prevent future Love Canals?
        • Pits in clay and disposal practices were acceptable under 1976 RCRA!!!
    • Love Canal - Significance
      • 1980: Congress passed Comprehensive Environmental Response, Compensation and Liabilities Act (CERCLA)
        • require clean up of uncontrolled waste sites
        • create Superfund to temporarily support efforts
      • RCRA given teeth
        • Hazardous and Solid Waste Amendments (1984)
        • Municipal Solid Waste Rules (1991)
        • Requirements for siting landfills
        • Requirements for engineered lining and cover systems (prevent leakage and bath-tub effect)
        • Ban on liquids in hazardous waste landfills
    • What is Solid Waste?
      • Waste: Any material that is discarded, served its intended purpose, or is a manufacturing or mining byproduct
      • Solid Waste: Everything not covered by the Clean Air and Water Acts, including solids, liquids and gases (RCRA is a catch all)
      Municipal Solid Waste (MSW) Industrial Waste (liquids) Combustion Residue (ash) Sewage Waste (sludge) Mining Waste Dredging Waste Agricultural Waste Radioactive Waste Special Waste
    • What is Hazardous Waste?
      • A waste is hazardous if…
      • It is not excluded by regulation
        • e.g., household waste, oil and gas drilling waste, etc.
      • It exhibits one of the following:
        • Toxicity, Ignitability, Corrosivity, Reactivity or Leachability
      • It is listed as a hazardous waste
        • e.g., K051: API separator sludge from petroleum refineries
      • It is mixed with or derived from a hazardous waste
    • Properties of Waste
      • Hazardous Waste (RCRA Subtitle C)
        • 90 % liquid
        • 60 % organic, 40 % inorganic
        • Waste must be treated with Best Demonstrated Available Technology (BDAT) before disposal
        • Product of treatment is typically a sand-like material (liquids banned in landfills after 1983)
      • Municipal Solid Waste (RCRA Subtitle D)
    • Siting Landfills
      • Natural Threats
        • earthquakes, landslides, floods
      • Environmental Impacts
        • wetlands, surface water, groundwater, air, endangered species
      • Social Issues
        • odors, noise, traffic, airports, aesthetics, industrial and population growth, historical/archaeological sites
      • Economic Issues
        • disposal costs, land development alternatives, tax base, permitting costs, construction/operation costs
    • Engineered Containment Waste Leachate Rainfall Leakage Groundwater Gas Cover System Lining System
    • Containment Systems Drainage Layer Barrier Layer (Liner) Infiltration Leakage Drainage and Collection Leakage = Infiltration - Drainage
    • Barrier Layers
      • Natural Soil Liners
        • typically clay
        • be wary of fissures
      • Compacted Soil Liners
        • also known as compacted clay liners (CCLs)
        • 2 to 5 feet thick
      • Geosynthetic Clay Liners
        • also known as GCLs
        • 0.5 inches of bentonite (a clay) between fabrics
      • Geomembranes
        • also known as flexible membrane liners (FMLs)
        • typically polyethylene (PE) or polyvinyl chloride (PVC)
        • 40 to 80 mils (1 mil = 0.001 inches) thick
    • Drainage Layers
      • Granular Soils
        • typically sands and gravels
        • 1 to 2 feet thick
      • Geosynthetic (Man-made) Materials
        • geonets: polyethylene ribs
        • geotextiles: polypropylene and polyester fabrics
        • pipes: polyethylene and stainless steel
    • Example Configurations Geomembrane Compacted Clay Composite Liner Primary Liner Double Liner System Primary Collection System Secondary Liner Secondary Collection System
    • Example Lining System Gravel (2 feet) Cushion Geotextile Geoemembrane Geosynthetic Clay Liner Filter Geotextile Geonet Geomembrane Compacted Clay (3 feet) Waste Leachate Collection Primary Liner Leak Detection Secondary Liner
    • Example Cover System Cover Soil (2 feet) Sand (1 foot) Geomembrane Vegetation Frost Protection Drainage Barrier Gas Collection Geosynthetic Clay Liner Sand (1 foot) Waste
    • Estimating Leakage Soil Q = Rate of Outflow h L Water
    • Darcy’s Law Hydraulic Gradient = h/L Outflow Rate, Q (Volume of Flow per Time) Sand Clay
    • Darcy’s Law Q is proportional to gradient, h/L Q is proportional to area of flow, A Q = K(h/L)A where K is hydraulic conductivity (the slope of the Q versus h/L plot)
    • Hydraulic Conductivity K (cm/s) Gravel 1 to 100 Sand 10 -3 to 1 Silt 10 -6 to 10 -3 Clay 10 -9 to 10 -6 Geomembrane 10 -12 to 10 -11
    • Example Calculations Problem: Estimate leakage rate through liner Clay Liner K = 1x10 -7 cm/s 3 feet 1 foot Leachate Groundwater Solution: Q/A = K(h/L) Q/A = (1x10 -7 cm/s)(4’/3’) = 1.3x10 -7 cm/s Q/A = 1,120 liters per hectare per day (lphd) Q/A = 120 gallons per acre per day (gpad)
    • Typical Leakage Rates Leakage Rate (gpad) Clay Liner 100 Intact Geomembrane 0.1 Typical Geomembrane 10,000 Composite Liner 1