In industries dealing with hazardous materials—ranging from oil and gas to agriculture and chemical manufacturing—environmental safety is non-negotiable. One of the most effective systems for minimizing the risk of contamination and ensuring regulatory compliance is secondary containment. Among the various materials used in these systems, polyethylene liners have emerged as a reliable, cost-effective, and environmentally friendly solution.
This comprehensive article explores how polyethylene liners are used in secondary containment systems, the technical features that make them so effective, the industries that rely on them, and how they contribute to environmental protection.
What is Secondary Containment?
Secondary containment refers to structures or systems designed to prevent hazardous substances from escaping into the environment in the event of a leak, spill, or failure of the primary container. It acts as a backup barrier, protecting soil, groundwater, and ecosystems from contamination.
Common forms of secondary containment include:
- Earthen berms lined with impermeable membranes
- Concrete sumps or dikes
- Double-walled tanks
- Portable spill pallets and basins
The key to any secondary containment system’s effectiveness is its ability to contain fluids over extended periods without degradation or failure. This is where polyethylene liners come into play.
What are Polyethylene Liners?
Polyethylene liners are flexible sheets made from high-density (HDPE), linear low-density (LLDPE), or low-density polyethylene (LDPE). These thermoplastic materials are engineered for durability, chemical resistance, and impermeability.
Depending on the application, polyethylene liners can be:
- Smooth or textured
- Single or double-layered
- Welded or seamed on-site
- Custom-fabricated to exact dimensions
They’re typically black to resist UV damage, although other colors may be used for visibility or identification.
Why Use Polyethylene Liners in Secondary Containment?
1. Chemical Resistance
Polyethylene liners resist a wide range of chemicals, including:
- Hydrocarbons (e.g., crude oil, gasoline)
- Acids and alkalis
- Fertilizers and pesticides
- Industrial solvents
This makes them suitable for industries that store and handle aggressive substances.
2. Low Permeability
One of the greatest threats to environmental safety is leakage through containment systems. Polyethylene has extremely low permeability to fluids and gases, ensuring no seepage occurs through the liner into the surrounding soil or groundwater.
3. UV and Weather Resistance
Polyethylene liners can withstand long-term exposure to sunlight, wind, and temperature extremes without losing integrity. Additives like carbon black enhance UV resistance, extending the life of liners installed in open environments.
4. Flexibility and Conformability
Polyethylene liners are flexible, which allows them to conform to uneven surfaces like earthen berms, concrete containment areas, or compacted subgrades. This flexibility ensures a tight seal and uniform coverage.
5. Cost-Effective Installation and Maintenance
Compared to concrete or steel containment systems, polyethylene-lined containment areas are much more affordable and faster to install. Additionally, maintenance is minimal, mostly involving routine inspections and minor patching if needed.
Common Applications of Polyethylene Liners in Secondary Containment
1. Oil & Gas Facilities
In upstream, midstream, and downstream oil operations, polyethylene liners are used in:
- Well pad containment
- Frac water ponds
- Pipeline drip trays
- Tank farms and refueling areas
These liners prevent hydrocarbons and wastewater from contaminating soil and groundwater.
2. Agriculture and Fertilizer Storage
In farming, secondary containment for bulk liquid fertilizer and pesticide tanks is mandated by provincial and federal regulations. Polyethylene liners:
- Line earthen containment berms
- Underlay tank pads
- Line lagoons or runoff containment ponds
They protect surrounding fields and water sources from harmful agricultural chemicals.
3. Mining Operations
Mining sites use polyethylene liners for tailings ponds, process water containment, and heap leach pads. The liners act as barriers between toxic substances and the environment.
4. Industrial Chemical Plants
Facilities that store acids, alkalis, solvents, and other hazardous materials use lined containment systems around:
- Storage tanks
- Chemical mixing stations
- Drums and IBC totes
5. Municipal and Wastewater Treatment
In treatment plants, liners are used in:
- Sludge lagoons
- Chemical feed containment
- Brine and effluent ponds
They prevent seepage into municipal water systems or the surrounding environment.
Technical Aspects: What to Consider When Using Polyethylene Liners
1. Liner Thickness
The thickness of polyethylene liners typically ranges from 20 mils to 120 mils (0.5mm to 3mm), depending on the severity of the containment requirements.
- Light-duty: 20–40 mils (temporary or small-scale containment)
- Medium-duty: 40–60 mils (agriculture, some industrial applications)
- Heavy-duty: 80–120 mils (oil & gas, mining, large-scale chemical storage)
2. Seam Welding and Integrity Testing
To ensure a leak-proof system, polyethylene liners are often welded on-site using thermal fusion or extrusion welding. After installation, seams are tested using:
- Air pressure tests (for double seams)
- Vacuum box tests
- Spark tests
These quality control steps are critical for environmental compliance.
3. Subgrade Preparation
Before laying down the liner, the subgrade (soil or surface) must be:
- Compacted and free of sharp objects
- Graded to allow for drainage
- Padded with a geotextile underlayer (in rough terrain)
A poor subgrade can puncture the liner or lead to uneven stress and eventual failure.
4. Anchor Trench and Ballasting
To keep liners in place and prevent wind uplift or movement during rain, an anchor trench is typically dug around the perimeter. Additional ballasting (e.g., sandbags or gravel) may be placed on top.
Regulatory Requirements and Industry Standards
In Canada and the U.S., various environmental and safety authorities mandate secondary containment for specific industries. These include:
- Canadian Council of Ministers of the Environment (CCME)
- Alberta Energy Regulator (AER)
- U.S. Environmental Protection Agency (EPA)
- Occupational Safety and Health Administration (OSHA)
- NFPA (National Fire Protection Association)
Requirements often specify:
- Minimum volume of secondary containment (typically 110% of the largest container)
- Chemical compatibility of liner material
- Frequency of inspections and recordkeeping
- Spill response protocols
Using polyethylene liners makes compliance easier due to their chemical resistance and proven performance.
Benefits of Using Polyethylene Liners in Secondary Containment
| Feature | Benefit |
|---|---|
| Chemical resistance | Suitable for corrosive and toxic substances |
| Durability | Lifespan of 20+ years with proper maintenance |
| Easy installation | Faster deployment than rigid or concrete systems |
| Cost-effective | Lower total cost of ownership over time |
| Low permeability | Prevents ground and water contamination |
| Scalability | Ideal for both small and large containment zones |
| Regulatory compliance | Helps meet federal/provincial/state environmental standards |
Environmental and Safety Considerations
Polyethylene liners contribute to sustainability in several ways:
1. Preventing Groundwater Contamination
Leaking fuels, oils, or chemicals can permanently contaminate groundwater reserves. Liners stop seepage and protect potable water sources.
2. Reducing Soil Remediation Costs
Without a liner, a spill can require expensive soil excavation and treatment. Containment liners localize spills, minimizing cleanup and restoration efforts.
3. Enabling Spill Recovery
Liners often allow for the recovery and reuse of spilled substances, especially in industries like agriculture and mining.
4. Minimizing Wildlife Exposure
Lined containment areas help reduce animal exposure to harmful substances, preventing harm to local ecosystems.
Case Study: Polyethylene Liners in Western Canada’s Oilfields
In Alberta, oilfields often use HDPE liners to line:
- Drilling mud pits
- Tanker staging areas
- Well pads
During the fracking boom, temporary containment berms lined with polyethylene were rapidly deployed to support fast-moving operations. Liners proved essential in avoiding fines and environmental penalties due to chemical leaks.
Thanks to polyethylene liners, companies met AER containment regulations and reduced their environmental liabilities.
Maintenance and Inspection Best Practices
Maintaining a secondary containment system with a polyethylene liner involves:
- Visual inspections (monthly or after heavy weather)
- Seam inspections (every 6–12 months)
- Checking for uplift, wrinkles, or punctures
- Routine cleaning of surface debris
- Spill response drills and documentation
Punctures can often be patched using extrusion welding or with repair kits specific to the liner type.
Choosing the Right Supplier and Installer
When selecting polyethylene liners and installation services, consider:
- Experience in your industry
- Certified welding technicians
- Compliance documentation (material test reports, QA/QC plans)
- Warranty (some offer 10–20 years)
- After-installation support
Working with trusted providers ensures long-term system performance and compliance.
Polyethylene liners are a cornerstone of modern secondary containment strategies. Whether in agriculture, oil and gas, chemical manufacturing, or wastewater treatment, these liners provide a durable, cost-effective, and regulatory-compliant way to protect the environment and public health.
Their combination of chemical resistance, low permeability, and flexibility make them an ideal material for a wide range of containment needs. As environmental regulations grow stricter and industries continue to prioritize sustainable practices, polyethylene liners will remain a key technology in responsible operations.