TOPIC:    Fugitive Landfill Gas – Lessons Learned

Each month Tim Stark introduces a new technical topic for discussion and possible action. This month’s topic is: “Fugitive Landfill Gas.” This topic generated significant discussion with the main “take-aways” listed below:

Objective of Landfill Regulations
‍-       No leachate reaching groundwater or surface water for Municipal Solid Waste (MSW) Landfills
-       No landfill gas emissions reaching atmosphere or migrating underground
-       No litter or slope movement

Subsurface Landfill Gas
‍-       Gas composition is mainly methane and carbon dioxide with small amounts of other gases
-       Gas emissions can contaminate groundwater
-       Methane is explosive so landfill should contain it because it can: (1) accumulate in structures and (2) displace oxygen, which can lead to asphyxiation

Fugitive Landfill Gas Case Study
‍-       Methane migration detected outside an MSW landfill even though geomembrane in bottom liner and cover systems
-       Landfill design was compliant with regulations, geomembranes were intact, and landfill operations were normal
-       Landfill did add a 10 ft high berm around MSW landfill to increase storage capacity

Fugitive Gas Detected
‍-       Gas detection probes ~50 ft (across access road from landfill) from MSW detected methane
-       Gas probes depths vary - to saturated soil/aquifer or to monitor a pathway
-       Ohio EPA exceeds Subtitle D by requiring more gas probes to monitor migration towards structures
-       Ohio EPA’s trigger for remediation is > 5% methane detected in gas probes, gas probes detected 10 to 15% methane
-       Detection resulted in investigation to determine how methane migrated outside of containment system
-       Groundwater wells are typically located further away – no groundwater contamination detected

Landfill Design and Discussion
‍-       Figure 1 shows typical landfill design with bottom liner and cover systems anchored close to each other; Ohio regulations do not require the two geomembranes be sealed to each other
-       Figure 2 shows MSW landfill design that includes 10 ft high berm to increase storage capacity but bottom liner and cover systems were not connected or sealed
-       Figure 3 shows postulated gas migration through 10 ft high berm to gas probe outside of the geomembrane cover system
-       Berm was not required to be lined because no waste is disposed above it

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