LANDFILL GAS CONTROL SYSTEMS: DESIGN AND CONSTRUCTION CONSIDERATIONS. Mike Bradford, P.E.

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1 LANDFILL GAS CONTROL SYSTEMS: DESIGN AND CONSTRUCTION CONSIDERATIONS Mike Bradford, P.E.

2 2 Today s Agenda SOLUTIONS YOU CAN COUNT ON. PEOPLE YOU CAN TRUST. What are we controlling? FOCUS: How do we control it? Design and Construction Considerations Why are we controlling it? $ Qualitative Cost Comparison

3 WHAT ARE WE CONTROLLING? Landfill Gas (LFG) Methane, Carbon Dioxide, Trace Gases Volitile Organic Compounds Sensitive To Moisture Slow Generation in Arid Climates WHY ARE WE CONTROLLING IT? Prevention Cover Damage Subsurface Migration (Post Closure Effects) Corrective or Remedial Action Groundwater Contamination Hazardous Accumulation in Structures Air Quality of Odor Control Regulatory Compliance Beneficial Reuse 3

4 How Do We Control It? Give the LFG a Preferred and Controlled Path of Migration

5 Types of Collection Passive and Active

6 Passive Collection

7 7 Passive Collection Targeted Remedial action for detection in perimeter probes or nearby structures Corrective action for detection in groundwater monitoring wells, Isolated Passive Vent or Vents

8 Passive Collection Vent Types Gooseneck Image

net/portfolio/vent-pipes/ Gooseneck Turbine Vent

gov/sites/production/files/region8/superfu

8 8 Passive Collection Vent Types Gooseneck Image from: Gooseneck Turbine Vent Image from: nd/nd/minot/passive_landfill_gas_vent.jpg Solar Spark Flare Image from:

9 Protection of Landfill Perimeter or Onsite Structure Thayne Landfill Remediation - Cut-Off Trench 9 Trench Barrier PVC Vertical Collection Layer Collection Manifold Vent

10 10 Full Coverage Protection of Barrier Type Final Cover Blanket Gas Collection Layer with Equally Spaced Passive Vents

11 Active Collection

12 12 Active Collection Targeted Corrective Action (same reasons as for passive systems) Stepped approach to remediation (i.e. convert passive to active) Vertical wells only Destroyed or Filtered Full Coverage Typically used to satisfy regulations Horizontal wells Vertical wells Destroyed only

13 Types of Active Collection Wells Horizontal vs. Vertical

14 Horizontal Collection Wells MUST BE PREPLANNED

15 Perforated pipe running the length of, and parallel to, the waste mass and connecting to a perimeter collection header (typically 6-inch in diameter)

16 Vertical and Horizontal Separation and Gallery Staggering

17 Vertical Collection Wells

18 Vertical Collection Wells Directly drilled into existing/in-place waste Borehole typically 2-3 feet in diameter Slotted or Perforated PVC or HDPE well casing

18 18 Vertical Collection Wells Directly drilled into existing/in-place waste Borehole typically 2-3 feet in diameter Slotted or Perforated PVC or HDPE well casing (typically 6-inch in diameter) Typically terminating feet from surface Typically no deeper than 75% of the waste depth if unlined, lined facilities can go deeper

19 Design & Construction Considerations

20 20 Well Spacing: What to Consider Radius of Influence Rule of Thumb 1 well per acre Vacuum provided by blower at wellhead Waste Characteristics Cell or trench configurations Cover systems Liquids ROI Overlap for redundant control eliminate dead zones Collection header alignment

21 21 Collection Pipe Design and Routing: What to Consider Material HDPE vs. PVC Do not recommend metal pipes Vacuum at the Wellheads Pipe size, bends, reducers effect loss of vacuum Minimum 4-inch diameter for laterals Minimum 6-inch diameter for headers Condensate Management Gas flow Direction Location Over Waste or Over Native Ground Facility Operational Plan Buried vs. At Grade (must be buried in cold climates) Road Crossings (i.e. protective sleeves) Facility s Development Plan Header loop Redundancy Isolation Valves Future Connections

22 22 Condensate Management: What to Consider Accumulation at Low Spots Can Restrict Flow and Reduce System Vacuum Freezing Disposal Options Condensate Traps vs. Condensate Sumps Electric vs. Pneumatic Waste Injection Evaporation Discharge to Leachate Ponds Flares Storage and Treatment

23 23 Blower-Flare Station Design: What to Consider Minimum vacuum required at wellheads (typically 5 inches water column) Design for buildout conditions with a Factor of Safety provide more vacuum than is necessary Typically inches water column provided Constant Vacuum Redundancy? Location Should be considered when designing header Is there adequate power Visibility Overhead hazards?

24 24 Landfill Gas Treatment Types Filtered, destroyed, or reused? Filtered Installed for remediation Strips VOC s and reduces odors. Destroyed Required with NSPS or EG driven systems Converted to Energy

25 Flare Types

26 26 Candlestick Flame (i.e. LFG Destruction) at top of flare Visible flames 98% destruction efficiency Cannot test flare effluent Smaller footprint, less expensive Image from:

27 Image from: 27 Enclosed Flame (i.e. LFG Destruction) near the ground Flames not visible 98% or more destruction efficiency Can test flare effluent Larger footprint, more expensive

28 28 Beneficial Use I.E. Covert to Power Typically voluntary by the community Invites regulatory oversight.

29 Qualitative Construction Costs Widely varies depending on size and scope of system Turbine Vents < Solar Flares Targeted < Full Coverage Horizontal Well < Vertical Well

29 29 Qualitative Construction Costs Widely varies depending on size and scope of system Turbine Vents < Solar Flares Targeted < Full Coverage Horizontal Well < Vertical Well Passive < Active Well Cost Dependent on Depth Piping cost dependent on size, length and buried vs. not buried Candlestick Flare < Enclosed Flare Long Term Operations and Maintenance

30 30 Wrap Up What is LFG? Why We Control LFG? How We Control LFG? Active Control Passive Control Design and Construction Considerations Vents Wells Piping Condensate Management Blower-Flare Stations Qualitative Construction Costs

31 Questions? WHAT WHY WHERE WHEN WHO HOW

A Public-Private Partnership to Advance Recovery and Use of Methane as a Clean Energy Source. Landfill Wellfield and Project Components

A Public-Private Partnership to Advance Recovery and Use of Methane as a Clean Energy Source Landfill Wellfield and Project Components Outline Objectives of LFG Collection/Control Elements of a LFG collection