lecture23

lecture23 - Lecture 23 Requirements for Landfill Closure...

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Lecture 23 Requirements for Landfill Closure and Monitoring
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Solid waste landfill closure under RCRA SUBTITLE D 6.2 FINAL COVER DESIGN 40 CFR §258.606.2.1 Statement of Regulation (a) Owners or operators of all MSWLF units must install a final cover system that is designed to minimize infiltration and erosion. The final cover system must be designed and constructed to: (1) Have permeability less than or equal to the permeability of any bottom liner system or natural subsoils present, or a permeability no greater than 1 x 10 -5 cm/sec, whichever is less, and (2) Minimize infiltration through the closed MSWLF unit by the use of an infiltration layer that contains a minimum of 18-inches of an earthen material, and (3) Minimize erosion of the final cover by the use of an erosion layer that contains a minimum 6-inches of earthen material that is capable of sustaining native plant growth.
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Solid waste landfill closure under RCRA Solid waste Topsoil (6 inches minimum) Vegetative Cover Infiltration Cover with K < 1 x 10 -5 (18 inches minimum)
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Closure of hazardous waste landfill Requirements for RCRA hazardous waste facilities (Subtitle C) are substantial: Includes multi-layer cap: Low hydraulic conductivity soil/geomembrane layer Drainage layer Vegetation soil layer Reference: U.S. EPA, 1991. Design and Construction of RCRA/CERCLA Final Covers. Report Number EPA/625/4-91/025. U.S. Environmental Protection Agency, Cincinnati, OH. May 1991.
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Closure of hazardous waste landfill Solid waste Geotextile Gas Vent Layer (optional) Geotextile Protection (cobble) layer Top Soil Cover Vegetative Cover Drainage Layer FML Geotextile Compacted clay
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Components of RCRA cap Vegetation layer Provides vegetation growth Provides erosion control Reduces infiltration by plant transpiration Protection layer is optional but provides: Freeze-thaw protection Medium for root growth Possibly rodent protection using cobbles
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Components of RCRA cap Drainage layer Drains infiltrated water Gravel or geonet Designed based on results of HELP model (usually with factor of safety) Low-permeability barrier layer Made of compacted clay, GCL, or composite 60-cm (2-ft) clay liner is considered minimum 40 mil minimum thickness
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Components of RCRA cap Gas vent layer Usually coarse grained sand or geonet or thick geotextile Provides stable layer for construction of barrier layer Maintenance issues (particularly for compacted clay liners): Desiccation cracking Freeze/thaw Differential settlement of waste and tensile cracking of cover
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Evapotranspiration landfill Relatively new alternative for capping landfills in arid areas Relies on evapotranspiration to keep moisture out of waste EPA Fact Sheet: http://www.epa.gov/superfund/new/evapo.pdf
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Monolithic ET cover Solid waste Fine-grained layer (silt or clayey silt) (2 feet to 10 feet) Vegetative Cover Interim cover
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Capillary barrier ET cover Solid waste Fine-grained layer (silt or clayey silt) (2 feet to 10 feet) Vegetative Cover Interim cover Capillary barrier (coarse- grained layer)
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This note was uploaded on 12/06/2011 for the course ESD 1.34 taught by Professor Petershanahan during the Spring '04 term at MIT.

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lecture23 - Lecture 23 Requirements for Landfill Closure...

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