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2.  Consider objectives Control migration of gas Control emission Control odors Maximize gas collection fir energy recovery Comply with regulations  Define limits of landfill Horizontal and vertical limits 2

3.  Gas extraction wells or trenches Well diameter and spacing Well materials(HDPE/PVC) and depth Non-well (leachate collection risers and trench systems) extraction points  Layout gas wells Shallow wells - small ROI Deep wells - large ROI Typically 150’ ROI (per NR 500) Liquid levels in landfill Affected by landfill design, permeability, waste type, and operating pressure/vacuum 3

4.  Locate gas header pipe Monitoring capability Liquid level accessibility Resistance to environmental effects Versatility after installation  Establish condensate management  Adjust gas wells, if needed  Prepare a well schedule (example) 0.5 to 1.5 cfm/slotted foot of pipe  Determine gas generation and flow 4

5.  Header and blower sizing calculations Calculate by hand Spreadsheet Computer model KY GAS (Hardy cross method)  Condensate Headers need to be sloped so condensate does not pool in them Need to size headers to carry condensate along with LFG Need to size the pipe Calculate by hand 5

6.  Condensate Management Structures Knock-outs Lift stations Barometric drip legs Transfer stations Drip legs - Potential for air intrusion Pneumatic vs. Electric Consequences of inadequate condensate management  Flooded headers  Low vacuum at well heads  Effectively reduces pipe diameter  Increased operating cost 6

7.  Select blower/flare system Calculate by hand Spreadsheet Computer model KY GAS (Hardy cross method) Enclosed vs. open (destruction efficiency, cost, and simplicity of operation) Sizing – gas rate, operating temperature, ignition source, etc. Capacity ranges (turndown capability) May be importance for some of the closed sites with very little gas 7

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9.  A velocity of 50 ft/sec is the maximum allowed during concurrent flow conditions  A velocity of 30 ft/sec is the maximum allowed during countercurrent flow conditions  A velocity of 30 ft/sec is the maximum allowed within condensate management structures  A pressure drop of 1 inch water column per 100 feet of header is the maximum allowed under any flow conditions 9

10.  Flow conditions within a header must not exceed either pressure loss nor velocity limitations  10 inches of vacuum required at furthest extraction well  10 to 20 inch loss of vacuum at blower flare station 10

11.  PVC Rigid Higher temperature Structurally functional when slotted Easy to extend Higher cost Variety of manufactured fittings  HDPE Los cost Very flexible Temperature effects 11

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13. 13 Landfill Gas Movement Patterns  Looping system Benefits vs. cost Designed to be redundant Accepts expansions  Control valves at strategic locations in header system Isolation portions of the system for maintenance, etc.  Types Butterfly, gate or other values

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17. 17 Vertical Gas Well Construction (1)

18. 18 Vertical Gas Well Construction (2)

19. 19 Vertical Gas Well Construction (3)

20. 20 Vertical Gas Well Construction (4)

21. 21 Vertical Gas Well Construction (5)

22. 22 Vertical Gas Well Construction (6)

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24. At some landfills, gas collection wells are installed after the facility reaches grade. At others, the gas collection network is continuously built and expanded. 24

25. Gas Collection Well 25

26. LFG Collection Pipe Systems 26

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31. Perimeter Vertical LFG Collection Well 31

32. Example of Radius of Influence Calculation 32 Q Extraction Well Grade D-S D S H Zone of Influence Landfill Bottom Isobars RIRI RwRw

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36. Leachate collection system retrofitted for gas collection 36

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40. 40 Bioreactor Traditional Time, yrs Methane Production Cfm of LFG Landfill closure