Solid Waste Landfills


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Solid Waste Landfills

  1. 1. Solid Waste Landfills Robert B. Gilbert Assistant Professor of Civil Engineering The University of Texas at Austin
  2. 2. Background <ul><li>More than 5,000 landfills in U.S. </li></ul><ul><li>More than 500 landfills in Texas </li></ul><ul><li>75 % of Municipal Solid Waste (MSW) ends up in a landfill (120 million tons/year) </li></ul><ul><li>Landfills are an economical solution </li></ul><ul><ul><li>$30/ton to landfill MSW (1992) </li></ul></ul><ul><ul><li>$52/ton for waste to energy of MSW (1992) </li></ul></ul><ul><li>Products of treatment (e.g., incinerator ash) must be landfilled </li></ul><ul><li>Hence, landfills are not going away </li></ul>
  3. 3. Regulations <ul><li>Specify what can and cannot be put into a landfill </li></ul><ul><li>Give design, construction and operation standards </li></ul><ul><li>Give environmental monitoring requirements </li></ul><ul><li>Drive the industry </li></ul>Investment ($) Profit ($) Permit
  4. 4. Regulations - History <ul><li>Environmental Activism in 1960’s </li></ul><ul><li>National Environmental Policy Act (1970) </li></ul><ul><li>Clean Air Act (1970) </li></ul><ul><li>Clean Water Act (1972) </li></ul><ul><li>Resource Conservation and Recovery Act (1976) </li></ul><ul><ul><li>Clean Air and Water Acts pushed waste to land </li></ul></ul><ul><ul><li>RCRA intended to close the loop </li></ul></ul><ul><ul><li>Defined waste as hazardous and non-hazardous </li></ul></ul><ul><ul><li>Initial focus was on hazardous waste </li></ul></ul>
  5. 5. Love Canal - Background <ul><li>William T. Love started a 7-mile long canal in 1890’s to harness power from Niagra Falls </li></ul><ul><li>Development of alternating current (which could be transmitted farther than direct current) made canal obsolete: only two 1/4-mile sections were excavated </li></ul><ul><li>AC power brought industry to area, particularly chemical companies </li></ul><ul><li>Hooker Chemical and Plastic Corp. manufactured plastics, chemicals and pesticides (chlorinated organic chemicals) </li></ul>
  6. 6. Love Canal - Background <ul><li>1930’s: Hooker began disposing waste in north section of canal </li></ul><ul><li>1947: other chemical companies, the city of Niagra Falls, and the U.S. government were using the canal as a landfill </li></ul><ul><li>1952: canal was closed and capped by Hooker </li></ul>
  7. 7. Love Canal - Plan View N Love Canal 1968 Expressway Niagra River Groundwater Flow A A’
  8. 8. Love Canal - Cross Section Canal Silt Clay Water Table Bedrock 0’ -10’ -40’ A A’
  9. 9. Love Canal - Problems <ul><li>1953: City of Niagra Falls ignores Hooker’s warnings and buys canal for a new grade school </li></ul><ul><li>1955: 99th Street School completed on top of canal and homes built around perimeter </li></ul><ul><li>1958: Children burned in puddle in playground </li></ul><ul><li>1959: Oily sludge oozing into basement of house </li></ul><ul><li>1968: Expressway built and problems increase </li></ul><ul><li>1974: Residential pool uplifted by yellow, blue and orchid colored groundwater </li></ul><ul><li>1975: Sink hole developed in playground </li></ul>
  10. 10. Love Canal - Response <ul><li>1975: City began investigating problems </li></ul><ul><ul><li>toxic substances in basement air </li></ul></ul><ul><ul><li>high levels of benzene, chloroform and trichloroethene in groundwater </li></ul></ul><ul><ul><li>high rates of birth defects/miscarriages </li></ul></ul><ul><li>City slow to react (Hooker employed 3,000 workers locally) </li></ul><ul><li>1977: Local and regional news began reporting about problems </li></ul><ul><li>8/2/78: Headline of New York Times about Love Canal; lead story on national television news </li></ul>
  11. 11. Love Canal - Resolution <ul><li>1978: 237 families relocated and school closed </li></ul><ul><li>1980: 700 more houses evacuated </li></ul><ul><li>1980’s: Hooker (now known as Occidental Chemical) and residents settled out of court for $30 million </li></ul><ul><li>1980’s: New cap placed on canal </li></ul><ul><li>Today: People are moving back to the area </li></ul>
  12. 12. Love Canal - Questions <ul><li>Who was responsible? </li></ul><ul><ul><li>Hooker </li></ul></ul><ul><ul><li>City of Niagra Falls </li></ul></ul><ul><ul><li>State or Federal Government </li></ul></ul><ul><ul><li>Other Landfill Users </li></ul></ul><ul><li>How many more Love Canals existed (ticking time bombs)? </li></ul><ul><ul><li>Over 1,000 national sites identified </li></ul></ul><ul><li>How can we prevent future Love Canals? </li></ul><ul><ul><li>Pits in clay and disposal practices were acceptable under 1976 RCRA!!! </li></ul></ul>
  13. 13. Love Canal - Significance <ul><li>1980: Congress passed Comprehensive Environmental Response, Compensation and Liabilities Act (CERCLA) </li></ul><ul><ul><li>require clean up of uncontrolled waste sites </li></ul></ul><ul><ul><li>create Superfund to temporarily support efforts </li></ul></ul><ul><li>RCRA given teeth </li></ul><ul><ul><li>Hazardous and Solid Waste Amendments (1984) </li></ul></ul><ul><ul><li>Municipal Solid Waste Rules (1991) </li></ul></ul><ul><ul><li>Requirements for siting landfills </li></ul></ul><ul><ul><li>Requirements for engineered lining and cover systems (prevent leakage and bath-tub effect) </li></ul></ul><ul><ul><li>Ban on liquids in hazardous waste landfills </li></ul></ul>
  14. 14. What is Solid Waste? <ul><li>Waste: Any material that is discarded, served its intended purpose, or is a manufacturing or mining byproduct </li></ul><ul><li>Solid Waste: Everything not covered by the Clean Air and Water Acts, including solids, liquids and gases (RCRA is a catch all) </li></ul>Municipal Solid Waste (MSW) Industrial Waste (liquids) Combustion Residue (ash) Sewage Waste (sludge) Mining Waste Dredging Waste Agricultural Waste Radioactive Waste Special Waste
  15. 15. What is Hazardous Waste? <ul><li>A waste is hazardous if… </li></ul><ul><li>It is not excluded by regulation </li></ul><ul><ul><li>e.g., household waste, oil and gas drilling waste, etc. </li></ul></ul><ul><li>It exhibits one of the following: </li></ul><ul><ul><li>Toxicity, Ignitability, Corrosivity, Reactivity or Leachability </li></ul></ul><ul><li>It is listed as a hazardous waste </li></ul><ul><ul><li>e.g., K051: API separator sludge from petroleum refineries </li></ul></ul><ul><li>It is mixed with or derived from a hazardous waste </li></ul>
  16. 16. Properties of Waste <ul><li>Hazardous Waste (RCRA Subtitle C) </li></ul><ul><ul><li>90 % liquid </li></ul></ul><ul><ul><li>60 % organic, 40 % inorganic </li></ul></ul><ul><ul><li>Waste must be treated with Best Demonstrated Available Technology (BDAT) before disposal </li></ul></ul><ul><ul><li>Product of treatment is typically a sand-like material (liquids banned in landfills after 1983) </li></ul></ul><ul><li>Municipal Solid Waste (RCRA Subtitle D) </li></ul>
  17. 17. Siting Landfills <ul><li>Natural Threats </li></ul><ul><ul><li>earthquakes, landslides, floods </li></ul></ul><ul><li>Environmental Impacts </li></ul><ul><ul><li>wetlands, surface water, groundwater, air, endangered species </li></ul></ul><ul><li>Social Issues </li></ul><ul><ul><li>odors, noise, traffic, airports, aesthetics, industrial and population growth, historical/archaeological sites </li></ul></ul><ul><li>Economic Issues </li></ul><ul><ul><li>disposal costs, land development alternatives, tax base, permitting costs, construction/operation costs </li></ul></ul>
  18. 18. Engineered Containment Waste Leachate Rainfall Leakage Groundwater Gas Cover System Lining System
  19. 19. Containment Systems Drainage Layer Barrier Layer (Liner) Infiltration Leakage Drainage and Collection Leakage = Infiltration - Drainage
  20. 20. Barrier Layers <ul><li>Natural Soil Liners </li></ul><ul><ul><li>typically clay </li></ul></ul><ul><ul><li>be wary of fissures </li></ul></ul><ul><li>Compacted Soil Liners </li></ul><ul><ul><li>also known as compacted clay liners (CCLs) </li></ul></ul><ul><ul><li>2 to 5 feet thick </li></ul></ul><ul><li>Geosynthetic Clay Liners </li></ul><ul><ul><li>also known as GCLs </li></ul></ul><ul><ul><li>0.5 inches of bentonite (a clay) between fabrics </li></ul></ul><ul><li>Geomembranes </li></ul><ul><ul><li>also known as flexible membrane liners (FMLs) </li></ul></ul><ul><ul><li>typically polyethylene (PE) or polyvinyl chloride (PVC) </li></ul></ul><ul><ul><li>40 to 80 mils (1 mil = 0.001 inches) thick </li></ul></ul>
  21. 21. Drainage Layers <ul><li>Granular Soils </li></ul><ul><ul><li>typically sands and gravels </li></ul></ul><ul><ul><li>1 to 2 feet thick </li></ul></ul><ul><li>Geosynthetic (Man-made) Materials </li></ul><ul><ul><li>geonets: polyethylene ribs </li></ul></ul><ul><ul><li>geotextiles: polypropylene and polyester fabrics </li></ul></ul><ul><ul><li>pipes: polyethylene and stainless steel </li></ul></ul>
  22. 22. Example Configurations Geomembrane Compacted Clay Composite Liner Primary Liner Double Liner System Primary Collection System Secondary Liner Secondary Collection System
  23. 23. 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
  24. 24. 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
  25. 25. Estimating Leakage Soil Q = Rate of Outflow h L Water
  26. 26. Darcy’s Law Hydraulic Gradient = h/L Outflow Rate, Q (Volume of Flow per Time) Sand Clay
  27. 27. 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)
  28. 28. 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
  29. 29. 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)
  30. 30. Typical Leakage Rates Leakage Rate (gpad) Clay Liner 100 Intact Geomembrane 0.1 Typical Geomembrane 10,000 Composite Liner 1