Landfill Project at Karnataka – Case Study

Ocean Non Wovens supplied 6000 sq m of Ocean HDPE Liner-1500micron for a landfill project in Karnataka. The liner forms the barrier between stored waste and the ground below, keeping leachate out of soil and groundwater.

Product – Ocean HDPE Liner-1500micron

Quantity – 6000 sq m

Location – Karnataka

The problem: what landfills do to air, water and wildlife

Landfilling is still the most widely used way to dispose of waste in India because it is cheap and needs only marginal land. Rising incomes and changing consumption have increased the amount of waste produced, so more of it ends up in landfills, and each site carries risks for the people and environment around it.

Groundwater and surface water. Rain that falls on the waste percolates through it and becomes leachate, a liquid carrying dissolved organics, salts and metals. Without a liner, leachate seeps into the subsoil and can contaminate the groundwater and nearby streams that communities rely on. Heavy rain on exposed waste or bare cover soil also erodes it and carries contaminated runoff off site.

Landfill gas. As organic waste decomposes it produces biogas, made up mainly of methane (CH4) and carbon dioxide (CO2), both greenhouse gases. Gas collection is often installed only after a landfill cell is closed, by which time the gas from the fastest-degrading waste has already escaped to the atmosphere. Horizontal collection systems installed while a cell is still operating capture more, but still only a share of the methane produced.

Odour and land value. Odour from landfills is hard to control fully and almost always affects nearby residents. Property values fall near these sites, which tends to push the burden onto poorer communities.

Birds. Landfills attract birds that feed on the waste and can swallow plastic, aluminium and other harmful material. The steady food supply has also led some migratory species to stop migrating and stay near landfills year-round.

The solution: an HDPE liner system

Geosynthetics are now standard in landfill liner systems. The liner’s job is to keep the leachate produced by the waste separate from the ground and water table below. A common base lining system has these layers, from the bottom up:

• A geosynthetic clay liner (GCL) or compacted clay in contact with the prepared subgrade
• An HDPE Liner (geomembrane) over the GCL, forming a composite barrier
• A heavy non-woven geotextile to protect the HDPE from puncture
• A gravel or sand drainage layer that carries leachate to collection pipes and sumps
• A lighter geotextile filter between the drainage layer and the waste, so fines do not clog the drainage stone

A 1500 micron (1.5 mm) HDPE geomembrane is the thickness most commonly specified for municipal landfill base liners. HDPE has very low permeability, resists the chemicals in leachate, and at this thickness can be joined by dual-track fusion welding and checked by air-pressure testing of each seam.

Geomembranes are also used to cap closed landfills. A cap stops rain from entering the waste, which reduces the volume of leachate to be treated, and traps landfill gas (LFG) so it can be collected. HDPE is used in caps, but more flexible polymers such as linear low-density polyethylene (LLDPE), PVC or flexible polypropylene (fPP) are often preferred there, because the waste settles unevenly and the cap must follow that differential settlement without being strained to the point of stress cracking. LLDPE and fPP, being less crystalline than HDPE, are far less susceptible to stress cracking.

See more landfill and containment projects on our case studies page.