Flexible Geomembranes to Reduce Leachate Generation

- See photographs of applications using geomembranes to reduce leachate generation by Brian Fraser

- Contaminated soil applications with geomembrane cover – 30 mil thick woven coated polyethylene geomembranes

- Geomembrane cover also controls soil loss due to wind erosion

- Landfill temporary cover before final cover system installation – prevent bird migration, soil loss due to wind erosion, leachate generation due to rainfall – Washington state application

- Can reduce leachate from 1,200 leachate trucks/year to 12 trucks/year, which results in considerable cost savings

- Mining applications includes lag cover for smelting process wastes to prevent chemical leaching and wind erosion

- Temporary covers for PFAS materials

- Another application is temporarily covering fly ash with a geomembrane

- Permanent final cover system for landfills

- Floating cover in Oregon to prevent rainfall from reaching a leachate holding pond or leachate treatment pond

- Typical materials
- 5 years or less duration = woven coated polyethylene GM
- 10 years = 30 – 40 mil LLDPE GMs
- 30 years = 30 – 40 mil PVC GMs for final cover systems with soil cover
- temporary covers = 12 – 34 mil string reinforced GMs

- NCRS standard for contaminated soil stockpiles – 20 mil reinforced GM for dredged material forcover

- Leachate containment with GMs to prevent migration

- Engineers are now considering the bottom liner and cover as a system and designs are considering ballasting as well as type of geomembrane

- If installing to prevent wind erosion, need appropriate ballasting with proper anchoring and tensioning and a soil perimeter berm

- Usually need a durability of at least 5 years

- Need to test field welded seams so need a CQA Plan

- Make sure cover and liner system panels are shingled to promote runoff if not welded

- Also consider surface water management techniques, e.g., berms, to reduce potential for leachate generation

- Another large application is new landfill cell construction – after installing the special waste layer, cover the new bottom liner system with a geomembrane, which covers ¾ of new cell with GM and fill cell in ¼ of new cell – typical size of a new cell is 5to 20 acres

- FGI should consider Brownfield applications in the future

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