Case Study: Ensuring Environmental Safety in Varanasi’s Landfill Project with Ocean Non Wovens’ Geosynthetic Solutions

For a municipal solid waste landfill in Varanasi, Uttar Pradesh, Ocean Non Wovens supplied and installed three products that together form the landfill’s lining system: Ocean Geosynthetics Clay Liner-5MM, Ocean Non Woven Geotextile PP 3.5 MM thickness, and Ocean HDPE Liner-1500 Micron, each covering 17,250 sqm.

Project overview

The landfill was designed to take a large volume of municipal solid waste with minimal environmental impact. The main task was to stop leachate, the contaminated liquid that forms as waste decomposes and rain percolates through it, from seeping into the soil and groundwater. Varanasi sits on the Ganga alluvial plain, where groundwater is shallow and widely used, so the barrier had to be reliable.

Ocean Non Wovens supplied and installed:

1. Ocean Geosynthetics Clay Liner-5MM: 17,250 sqm
2. Ocean Non Woven Geotextile PP 3.5 MM Thickness: 17,250 sqm
3. Ocean HDPE Liner-1500 Micron: 17,250 sqm

How the three layers work together

These three products make up a standard composite liner. In the usual arrangement, from the bottom up: the GCL sits on the prepared subgrade, the HDPE liner is laid directly on the GCL, and the thick non-woven geotextile goes over the HDPE to protect it from the drainage aggregate and waste above. The HDPE and GCL have to be in direct contact. If the geomembrane develops a small hole, the bentonite beneath it limits how far leachate can spread and how fast it can pass, which is why a composite liner leaks far less than either material alone.

Ocean Geosynthetics Clay Liner-5MM

A geosynthetic clay liner (GCL) is a layer of sodium bentonite held between two geotextiles, usually needle-punched together. When the bentonite hydrates it swells into a dense gel with a hydraulic conductivity typically in the range of 1×10⁻¹¹ to 5×10⁻¹¹ m/s. At 5MM thick it replaces a much thicker layer of compacted clay, and it self-seals around small punctures. GCLs are specified and tested under ASTM D5887 (flux), D5890 (swell index) and D5891 (fluid loss).

Ocean HDPE Liner-1500 Micron

The HDPE geomembrane is the primary impermeable barrier. High-density polyethylene resists the wide range of chemicals present in leachate, and at 1500 micron (1.5 mm) it has the puncture resistance and stress-crack margin a landfill base needs under heavy waste loads. 1.5 mm is also the minimum geomembrane thickness in Indian practice for MSW landfill liners.

Ocean Non Woven Geotextile PP 3.5 MM

The thick polypropylene non-woven geotextile protects and filters. Laid over the HDPE, it cushions the geomembrane against the angular stone of the leachate drainage layer and against construction traffic. As a filter, it keeps fine particles out of the drainage layer so leachate can keep flowing to the collection pipes. A blocked drainage layer lets leachate build up head on the liner, which raises the risk of leakage. At 3.5 MM thickness it keeps its protective and filtering function under the weight of the waste.

Design and installation challenges

Differential settlement. Different parts of a landfill settle at different rates, stressing the liners. Ocean Non Wovens selected materials with the flexibility and tensile strength to accommodate minor shifts without compromising the containment system.

Interface shear strength. Layered geosynthetics can slide on one another, especially on side slopes and when the GCL is hydrated. The friction at each interface (GCL to HDPE, HDPE to geotextile) is checked by direct shear testing to ASTM D5321 (D6243 for the GCL’s internal strength), and textured HDPE is used where slopes demand it. The materials on this project were chosen with compatible surfaces to reduce the risk of slippage.

Installation. On a site of this size, each layer has to go down without damage. A GCL must be covered before it hydrates in the open, the HDPE welded and seam-tested, and the protection geotextile overlapped fully before aggregate is placed. Ocean Non Wovens used skilled technicians and suitable equipment for each stage.

Work with Ocean Non Wovens

Ocean Non Wovens manufactures and supplies geosynthetics for landfill lining, including GCLs, HDPE geomembranes, protection geotextiles and drainage geocomposites. Contact our team about the lining system for your next landfill cell.