The Use of Risk Assessment in Closure and Redevelopment by kfm14657

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									            The Use of
    Risk Assessment in Closure
       and Redevelopment of
             Landfills
                James R. Yardley, P.Eng.
       MGI Limited/ Conestoga-Rovers & Associates

Atlantic PIRI-NEIA
Contaminated Properties Conference
September 22, 2004
                 Overview

Ø   Landfill Development
Ø   Risk Management
Ø   Environmental Considerations
Ø   Closure and End Use
             Landfill Development

Ø Waste disposal sites and facilities evolve over
  time
Ø Each waste disposal facility has unique
  environmental risks
Ø Waste disposal areas are within urbanized areas
               1st Generation Facilities

Ø Commonly known as dumps
Ø Traits
    – minimal to no controls
    – small and remote
    – pre-1980 for large service areas
              2nd Generation Facilities

Ø Engineered Landfills
Ø Traits
    – engineered controls for environmental items
      (leachate, gas, surface water, etc.)
    – large facilities - close to urban areas
    – monitoring networks
    – integrated features
An Integrated Landfill
           3rd Generation Facilities

Ø The future of waste management
Ø Disposal is one component of the system
Ø Integration of waste management components
Ø Municipal vs. Industrial components
Ø Bioreactors, composting, multi-media resource
  recovery facilities, incineration
Ø Waste specific-processes
Today’s Waste Management System
– an integrated waste management complex
           Closed Landfills and Risk

Ø Does not fit within the Federal and Provincial
  risk assessment guidelines or Brownfields
Ø Risk exposure dependent on after use and time
  period since closure
Ø Decision approach - setting of priorities -
  documentation of decisions
Ø Regulatory compliant
        Risk Management for Closed Landfills

Ø   Key Factors
    –   surrounding land use - current and future
    –   end use - current and future
    –   holistic approach - not component
    –   subjective
           Environmental Considerations
     Medium                 Exposure Medium                  Potential Exposure/Risk
                              Surface seeps                   Human/animal contact
                      Collection system entry points          Surface water impacts
     Leachate               Treatment systems                 Groundwater impacts
                           Monitoring networks                   Physical contact
                         Subsurface excavations                     Indoor air
                                Ambient Air                       Odour impacts
   Landfill Gas       Migration into on-site structures        Explosive conditions
                      Migration into off-site structures       Vegetation stress/kill
                        Migration into off-site areas      Oxygen depletion conditions
                                                                    Indoor air
Settlement/Erosion/           Re fuse exposure                Human/animal contact
   Slope Stability              Slope failure
               Leachate - Key Factors
Ø Infiltration into waste (cover system)
Ø Degradation/ solubilization of the waste
Ø Waste disposal area design/ fill method
Ø Control relates to:
    –   unacceptable releases to the environment
    –   leachate seeps
    –   leachate generation volumes
    –   leachate strength
         Potential Leachate Issues
Ø Nuisance odours
Ø Degradation of surface water & groundwater
Ø human/animal exposure
Ø control and treatment system access
Ø monitoring networks
           Control Considerations
Ø Cover system
Ø Waste age
Ø Volume and type of waste
Ø Moisture level
Ø Landfill design and operations
Ø Interrelationship of the landfill components
         Leachate Control Methods
Ø Barrier systems
Ø Natural attenuation and treatment
Ø Collection and treatment
Ø Volume reduction
             Landfill Gas - Key Factors
Ø Generation - biodegradation of organics
Ø Main gases - methane & carbon dioxide
Ø Methane is low BTU fuel & greenhouse gas
Ø Control relates to:
    –   odour and explosive gas migration
    –   health and safety concerns
    –   greenhouse gas reduction
    –   energy use
Potential Landfill Gas Issues
                      Typical Landfill Gas Collection
               3500
                                                                                             Landfill Gas Collected
                                                                                             Collection System Not Installed
               3000                                                                          Landfill Gas Released


               2500
Landfill Gas




               2000


               1500

               1000
                                                                                                             Threshold Level

               500

                 0
                      0
                          3
                              6
                                  9
                                      12
                                           15
                                                18
                                                     21
                                                          24
                                                               27
                                                                    30
                                                                         33
                                                                              36
                                                                                   39
                                                                                        42
                                                                                              45
                                                                                                   48
                                                                                                        51
                                                                                                              54
                                                                                                                   57
                                                                                                                        60
                                                                                                                               63
                                                                    Years
           Control Considerations
Ø Gas composition phase
Ø Waste age
Ø Volume and type of waste
Ø Moisture level
Ø Landfill design and operations
Ø Interrelationship of the landfill components
       Landfill Gas Control Methods
Ø Barrier systems
Ø Passive controlled release systems
Ø Active collection systems
            Settlement/Erosion -
                Key Factors
Ø Waste composition and type
Ø Cover system
Ø Side slope grade
               Potential Issues
Ø Settlement of cover/cap
Ø Slope failure
Ø Erosion of cover by stormwater
Ø Waste exposure
           Control Considerations
Ø Cover system
Ø Waste age and type
Ø Moisture level
Ø Landfill design and operations
Ø Interrelationship of the landfill components
              Control Methods
Ø Moisture removal
Ø Waste re-distribution
Ø Regular inspection & maintenance
         Waste Disposal Site End Use

Ø Abandoned lands
Ø Natural regeneration areas
Ø Passive or active park/recreation areas
Ø Industrial/commercial areas
Ø Residential areas
          Development Guidelines
Ø The use of a closed waste disposal site will
  always change and evolve
Ø Minimize the use of hollow components in
  fences & playground equipment
Ø Keep structures above grade
Ø Settlement will always occur
Ø Landfill gas will always migrate
                 Summary
Ø Initial assessment is subjective
Ø Any use must account for special concerns,
  such as landfill gas, settlement, seepage and
  cover
Ø Risk assessment can use components of
  detailed regulated/guideline methods
Jim Yardley           jyardley@craworld.com
Conestoga-Rovers & Associates
651 Colby Drive, Waterloo, Ontario N2V 1C2
Phone: 519-884-0510      www.craworld.com

MGI Limited
1118 Topsail Road, St. John’s, NF A1B 3N7
Phone: 709-364-5353   www.mgi-limited.com

								
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