Landfill and Lagoon Liners
Liners keep leachate, wastewater and process liquids from escaping into soil and groundwater. Options include clay, factory geomembranes and spray-applied elastomeric liners formed on geotextile.
Landfill and lagoon liners are low-permeability barriers installed beneath and around waste disposal cells, lagoons, ponds, wastewater basins and process water impoundments. They prevent leachate, manure, wastewater, brine and other liquids from moving into soil and groundwater. Liners may be made from compacted clay, geosynthetic clay liners, factory-manufactured geomembranes, or spray-applied elastomeric membranes formed in place, often on geotextile fabric. Many installations combine several of these layers.
Where liners are used
- Municipal solid waste landfills, both bottom liners and final caps.
- Industrial and hazardous waste landfills.
- Wastewater lagoons at municipal and industrial plants (see water and wastewater coatings).
- Agricultural manure lagoons and digesters.
- Stormwater and detention ponds (see stormwater infrastructure coatings).
- Mining and process ponds, such as leach pads and tailings.
- Decorative and irrigation ponds.
- Secondary containment around tanks (see secondary containment coatings).
Regulatory context
Landfill and many lagoon liners are regulated. In the United States, rules for municipal solid waste landfills specify liner and leachate collection requirements, and state agencies regulate lagoons and industrial impoundments. Engineers design liners to meet these requirements, and installation is usually subject to construction quality assurance (CQA) plans. Specific requirements depend on jurisdiction and facility type.
Liner types
Compacted clay liners
Layers of clay compacted to low permeability. Often used beneath geomembranes in composite liners.
Geosynthetic clay liners (GCL)
Factory-made panels of bentonite clay between geotextiles. They swell when hydrated to form a seal.
Geomembranes
Factory sheets of polymers such as HDPE, LLDPE, PVC or reinforced polypropylene, welded on site. They are the most common landfill liners.
Spray-applied liners
Elastomeric coatings, typically polyurea or polyurea hybrids, sprayed onto geotextile fabric laid over the prepared subgrade, or directly onto concrete and other substrates. The result is a seamless, fabric-reinforced membrane (see coating geotextile fabric). Spray-applied liners are often used for lagoons, ponds, containment areas, wastewater basins, repairs and complex geometries. ArmorThane’s EnviroThane, for example, is a polyurea hybrid sprayed on geotextile for landfill, pond and wastewater liners. Further context is on ArmorThane’s municipal wastewater opportunities page.
Composite and double liner systems
Many landfills use composite liners, combining a geomembrane with compacted clay or a GCL. Some facilities use double liners with a leak detection layer between them. Leachate collection layers of gravel and pipe sit above the liner to remove liquids.
Installation of spray-applied liners
- Subgrade preparation. Compact, smooth and remove sharp objects.
- Anchor trench around the perimeter.
- Geotextile deployment with specified overlaps.
- Detail work at pipes, inlets and structures.
- Spray application in multiple passes to build specified thickness.
- Inspection and testing.
- Anchor trench backfill and cover, if designed.
Testing and quality assurance
- Thickness measurements and coverage tracking.
- Holiday or spark testing where the system allows (see holiday testing).
- Visual inspection for unwetted fabric, wrinkles and pinholes.
- Adhesion at concrete and pipe terminations.
- Leak location surveys, electrical methods for some geomembrane systems.
- Material testing of samples for properties such as tensile and tear strength.
- CQA documentation for regulated projects.
Chemical compatibility
Leachate, manure, industrial wastewater and brines contain varied chemicals. Liner materials must be tested or confirmed compatible with the specific liquid and temperature (see chemical resistance testing). Biogas from landfills and digesters can also affect materials and design.
Design issues
- Slope stability and interface friction between layers.
- Gas and groundwater below the liner; vents and underdrains may be needed to prevent uplift.
- UV exposure of uncovered liners; UV-stable materials or cover soils may be required (see aliphatic vs aromatic coatings).
- Mechanical protection from equipment, ice and animals.
- Penetrations and structures.
Maintenance
- Inspect exposed liners regularly for damage, especially at water lines, inlets and slopes.
- Remove debris and vegetation.
- Repair damage promptly with compatible materials.
- Monitor leak detection systems where present.
In practice
In practice, liner projects are driven by regulations and engineering design. Many landfill liners must meet specific state and federal requirements, and lagoon liners for wastewater or agricultural use may have their own rules. The engineer selects the liner system, then the installer prepares the subgrade and installs the liner under a quality assurance plan. Testing of seams or coating thickness and continuity is documented. Spray-applied liners are often used for repairs, complex shapes and penetrations, as well as for full liners where suitable.
Key terms
- Landfill cell. An engineered area for waste disposal with liners and leachate collection.
- Leachate. Liquid that drains through waste and may carry contaminants.
- Lagoon. An earthen basin used to store or treat water or wastewater.
- Geomembrane. A synthetic liner sheet, such as HDPE.
- Containment. Preventing stored material from escaping to soil or groundwater.
- Spray-applied liner. A seamless liner applied as a liquid, often polyurea.
- Subgrade. The prepared soil or base on which a liner is placed, which must be smooth, compacted and free of sharp objects.
Frequently asked questions
Can a spray liner be used in a landfill?
Spray-applied liners are used in some landfill applications, but regulated liners must meet design and permit requirements. The engineer and regulator decide what is acceptable.
How are spray liners repaired?
Damaged areas are cleaned, sometimes with fabric added, and resprayed according to the manufacturer’s procedure.
Related entries
- Secondary containment coatings
- Water and wastewater coatings
- Waterproofing membranes
- Holiday testing
- Coating geotextile fabric (new)
- Stormwater infrastructure coatings (new)
Educational reference. Coating performance varies by formulation. Always follow the manufacturer’s product data sheet, safety data sheet and your project specification.
