Geosynthetic Clay Liner – 6000 Sq mtr and HDPE Geomembrane – 6000 sq mtr to Jharkhand (Waste Management Project)

For a waste management project in Jharkhand, Ocean Non Wovens supplied 6000 sq mtr of Geosynthetic Clay Liner (GCL) and 6000 sq mtr of HDPE Geomembrane. Used together, the two materials form a composite liner that keeps leachate from the waste out of the soil and groundwater, and controls the migration of landfill gas.

Product: Geosynthetic Clay Liner – 6000 Sq mtr and HDPE Geomembrane – 6000 sq mtr

Location: Jharkhand

Problem

Waste generation rises with population, and without engineered disposal it ends up dumped on open land. Rainwater percolating through the waste becomes leachate, a liquid carrying dissolved organics, salts and sometimes heavy metals. On an unlined site it seeps into the ground, polluting groundwater and degrading the soil.

Landfills in Jharkhand had known gaps of this kind, with groundwater pollution, soil degradation and land pollution as the result. The state government’s waste management drive set out to deal with the threat to the environment and to public health.

Solution

Compacted clay was the traditional landfill liner. Since the 1980s, HDPE geomembranes and, later, geosynthetic clay liners have been used in its place or alongside it, because they give much lower permeability in a thinner, factory-controlled layer. On this project the two were used as a pair.

• HDPE geomembrane: A continuous, effectively impermeable polyethylene sheet, welded at the seams. It has high strength, flexibility, chemical resistance and weathering resistance, and its panels are heat-welded together, so no adhesives are needed.
• Geosynthetic clay liner: A layer of sodium bentonite held between two geotextiles. When the bentonite takes up water it swells into a dense gel with a hydraulic conductivity typically in the range of 1×10⁻¹¹ to 5×10⁻¹¹ m/s.

Placed directly under the geomembrane, the GCL backs up the sheet. Leakage through a geomembrane happens at small defects such as pinholes or a poor weld. With a low-permeability clay layer in close contact beneath it, water passing through a defect cannot spread out under the sheet, so the leakage rate drops sharply compared with either layer on its own.

This composite approach is what Indian rules call for. Schedule I of the Solid Waste Management Rules, 2016 specifies a composite base liner for sanitary landfills: a 1.5 mm HDPE geomembrane (or equivalent) over 90 cm of compacted clay or amended soil with a permeability not greater than 1×10⁻⁷ cm/s. A GCL is commonly used as an equivalent to all or part of that clay layer where good clay is scarce or space is limited.

Both materials are quicker to install than thick clay layers and, properly covered, last for the life of the landfill. A landfill liner of this kind is typically completed with a geotextile cushion over the geomembrane and a leachate drainage layer above it.

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