Geomembrane

A geomembrane is a thin polymer sheet with very low permeability, laid as a barrier to stop water, leachate, chemicals or gas from moving through soil. Ocean Geosynthetics, established in 1998 in New Delhi, manufactures and supplies HDPE geomembranes for landfills, ponds, canals, reservoirs, mining pads and industrial containment across India, along with LDPE sheets and waterproofing sheets for lighter-duty and building work.

This page is an overview of geomembrane types, the properties engineers specify, where each type is used and how to pick a thickness. For the full property table of our HDPE sheet by thickness (smooth and textured), see HDPE sheets. For farm, fish and water-storage ponds, see pond liners.

What is a geomembrane?

A geomembrane is a synthetic liner used with soil, rock or other geotechnical materials to control the migration of a fluid (or gas) in a man-made structure or system. Geomembranes can be made by spraying asphalt, elastomer or polymer onto a fabric, or as multilayer bituminous geocomposites, but by far the most common form is a continuous extruded polymer sheet. HDPE is the most widely used of these, followed by LLDPE, PVC, EPDM and reinforced polypropylene.

The sheet itself is close to impermeable. In practice, leakage through a lined facility comes from holes: punctures from stones in the subgrade, defective seams, and tears at anchor trenches and pipe penetrations. Most of what goes into specifying a geomembrane (thickness, puncture resistance, protection layers, seam testing) is about preventing those holes.

Types of geomembranes

HDPE geomembrane

High-density polyethylene is the most widely used geomembrane because it combines long service life, good UV resistance (from 2–3% carbon black), broad chemical resistance and relatively low material cost. It is the standard choice for exposed applications such as landfill liners, reservoir and pond liners and canal linings, and it is made in heavier thicknesses than most other types. GRI-GM13 requires a formulated sheet density of at least 0.940 g/cc. HDPE is stiffer than the other polyethylenes, so it needs smooth, well-prepared subgrade and attention to wrinkles caused by thermal expansion.

Polyethylene is chemically inert and widely used for drinking-water storage, but a liner for potable water should be a grade certified for that use (for example to NSF/ANSI 61). Ask for the certificate if your project needs one.

LDPE geomembrane

Low-density polyethylene is softer and more flexible than HDPE, which makes it easier to fit over irregular ground and into tight details. It has lower tensile strength and lower resistance to some hydrocarbons and solvents than HDPE. LDPE sheets are used for farm ponds, canal and watercourse lining, moisture barriers under slabs and temporary containment. See LDPE sheets for grades.

LLDPE geomembrane

Linear low-density polyethylene (covered by GRI-GM17) is more flexible than HDPE and tolerates more out-of-plane strain before failing, which suits landfill caps over settling waste, animal-waste lagoons and liquid storage where the subgrade will move. Like HDPE, it is made from virgin polyethylene resin; its UV resistance comes from carbon black and stabilizers added to the formulation.

PVC liners

Polyvinyl chloride geomembranes are made from PVC resin compounded with plasticizers and stabilizers. (The resin itself comes from vinyl chloride monomer, produced by cracking ethylene dichloride, which is then polymerized.) PVC is very flexible, light and easy to fold and fabricate into large panels, and it resists tears, punctures and abrasion. It is used for canal and tank linings, soil remediation, wastewater lagoons and landfill caps. It needs a soil or other cover, because UV exposure and plasticizer loss stiffen it over time.

EPDM liners

EPDM (ethylene propylene diene monomer) is a synthetic rubber sheet: very flexible, UV-stable and tolerant of rough handling and weather. It is used as a surface barrier on dams and irrigation structures, for irrigation ponds and covers, and in landscaping because it is easy to install. Seams are made with tape or adhesive rather than heat welding.

RPP geomembrane

Reinforced polypropylene is a UV-stabilized polypropylene compound coated on both sides of a polyester scrim. The scrim gives dimensional stability and tear strength, so RPP copes well with folding and with exposed service where weather changes cause repeated movement. Typical uses are municipal water containment, aquaculture and horticulture, evaporation ponds, industrial waste and mine tailings.

TRP geomembrane

TRP geomembranes are similar to RPP but use a woven polyethylene fabric in place of the polyester scrim. They are light and economical, have good chemical resistance and UV stability within a limited temperature range, and are often used for temporary ponds, industrial tarps, soil remediation, canals, agriculture and municipal work. In India, laminated woven HDPE geomembranes of this kind are covered by IS 15351.

Properties of geomembrane and how they are tested

Geomembrane tests fall into two groups. Index tests (thickness, density, tensile, tear, puncture) are used for quality control and for comparing products. Performance tests (interface shear, axisymmetric tension, long-term durability) feed design. For HDPE, GRI-GM13 lists the index tests and minimum values by thickness; in India, HDPE geomembranes for lining are specified under IS 16352:2020, which covers smooth and textured sheet.

Physical properties

• Thickness: ASTM D5199 for smooth sheet; ASTM D5994 (core thickness) for textured sheet, with asperity height measured by ASTM D7466.
• Density: ASTM D1505 or D792. HDPE sheet must be 0.940 g/cc or more under GRI-GM13.
• Melt flow index: ASTM D1238, checked on the resin.
• Mass per unit area: follows from thickness and density; a 1.5 mm HDPE sheet weighs about 1.4 kg/m².

Mechanical properties

• Tensile strength and elongation: ASTM D6693 Type IV for HDPE and LLDPE (yield and break). Wide-width, axisymmetric and seam tests are also used.
• Tear resistance: ASTM D1004.
• Puncture resistance: ASTM D4833 (index puncture).
• Impact resistance.
• Interface shear strength: ASTM D5321, run with the actual soils and geosynthetics on the project. This governs slope stability for lined side slopes and caps.
• Anchorage strength: pull-out capacity of the anchor trench.

Durability properties

• Carbon black content and dispersion: ASTM D4218 (2–3% required for HDPE) and ASTM D5596.
• Oxidative induction time (OIT): standard OIT by ASTM D8117 or high-pressure OIT by ASTM D5885, a measure of the antioxidant package.
• Stress crack resistance: ASTM D5397 (notched constant tensile load), at least 500 hours for HDPE under GRI-GM13.
• Oven ageing and UV resistance: ASTM D5721 and ASTM D7238, reported as OIT retained.

Why HDPE is the default choice

• Mechanical strength: a 1.5 mm GM13 sheet has a minimum yield strength of 22 kN/m.
• Chemical stability: resists acids, alkalis, salts and most leachates.
• Puncture resistance that rises with thickness, plus a geotextile cushion where the subgrade is angular.
• Very low permeability of the intact sheet; leakage control depends on seam quality.
• Fast construction: wide rolls and wedge welding cover large areas quickly.
• Ageing and weather resistance from carbon black and antioxidants.
• Low cost per square metre compared with clay liners or concrete lining.
• Long service life: GRI White Paper 6 estimated a half-life of roughly 450 years for a covered 1.5 mm HDPE sheet at 20 °C. Exposed sheet ages much faster, so cover or protect it where you can.

Applications

Geomembranes are used to contain hazardous waste, line secure landfills, store water, prevent liquid contamination and help stabilize earth works by keeping water out of them.

Landfill liners

Geomembranes line landfills for municipal solid waste (MSW), low-hazard industrial waste, construction and demolition (C&D) debris and other non-hazardous industrial waste, and are used to close coal ash ponds. In India, Schedule I of the Solid Waste Management Rules, 2016 calls for a composite base liner of 1.5 mm HDPE geomembrane (or equivalent) over 90 cm of clay or amended soil with a permeability no greater than 1 × 10⁻⁷ cm/s. A geosynthetic clay liner is often used in place of or alongside the clay layer, and a drainage geocomposite or geonet above the liner collects leachate.

Caps and closures

Permanent landfill caps are strained in every direction by differential settlement of the waste and by gas pressure building up underneath. Caps usually sit on slopes and have to hold drainage geosynthetics and cover soil in place for decades, so interface friction and elongation matter more here than in a base liner. Flexible sheets (LLDPE, PVC) and textured HDPE are common choices. Covers keep rainwater out, reduce wind and water erosion of the material below, and help control odour.

Short-term covers include soil remediation sites, temporary stockpile covers and erosion protection on slopes during construction. Geomembranes are also used to extend the life of roofs on above-ground storage tanks.

Ponds and reservoirs

HDPE is the usual liner for irrigation ponds, fish and shrimp ponds, raw-water reservoirs and effluent lagoons. Panels are fusion welded in the field into a continuous sheet, which needs a trained welder and proper equipment. Liners that look alike can perform differently, so specify against a published standard: the Geosynthetic Institute (GRI) publishes the test methods and specifications widely used for HDPE liners. Pond-specific grades and sizes are on our pond liner page.

Mining and heap leach pads

In heap leaching the HDPE liner is the main barrier between the leach solution and the ground. The design has to account for chemical attack, point loads from very high ore heaps, and site-specific terrain, climate and construction conditions. Where suitable clay is scarce on site, a geomembrane with a GCL is a cost-effective composite liner.

A GCL is a layer of bentonite held between two geotextiles. At around 5–10 mm thick it is commonly used as an alternative to a compacted clay liner of 60–90 cm, and bentonite swells to seal small punctures. A nonwoven geotextile protection layer above the geomembrane spreads point loads from the overburden and keeps gravel and fines off the sheet.

Canal lining

Geomembranes cut seepage losses from irrigation canals. PVC, HDPE, LDPE, CSPE and EPDM have all been used. Canal liners usually need protection from people, animals, debris and maintenance equipment: compacted earth, concrete or shotcrete placed over the sheet. The US Bureau of Reclamation’s Deschutes Canal-Lining Demonstration Project in Oregon tested 34 canal test sections, many of them using geomembranes, and is a useful reference on how exposed and covered linings hold up over time. In India, IS 9698 is the code of practice for lining canals with polyethylene film.

Industrial and oil containment

HDPE lines oil pits, chemical storage areas, ETP lagoons and secondary containment bunds, where its chemical resistance matters more than flexibility. Ocean examples include an oil pit reservoir in Assam lined with 1.5 mm HDPE and a chemical containment project in West Bengal.

How to choose a geomembrane

• Start with the regulation. MSW landfills in India need 1.5 mm HDPE (or equivalent) in the base liner. Check CPCB or state pollution control board conditions for hazardous waste and industrial lagoons.
• Match the polymer to the liquid. HDPE for leachate, chemicals and hydrocarbons; LLDPE or PVC where the subgrade will settle or the sheet must bend over tight details.
• Size thickness for puncture and life, not just head of water. Thicker sheet resists puncture and installation damage better and leaves more margin for welding. Ocean has supplied HDPE from 500 micron for water ponds (for example a 500 micron pond liner in Patna) to 1.5 mm for landfills such as the Srinagar landfill.
• Smooth or textured. Use textured sheet on side slopes and caps where interface friction controls stability, and confirm with ASTM D5321 shear tests on project materials.
• Exposed or covered. Exposed liners need UV resistance (carbon black, HP-OIT retained after UV ageing) and allowance for wind uplift. Covering the sheet with soil extends its life considerably.
• Protection layer. On angular or gravelly subgrade, place a nonwoven geotextile under the liner and, where cover soil contains stones, above it.

Installation basics

1. Subgrade: compacted, smooth and free of roots, stones and standing water. Round off sharp changes in grade.
2. Anchor trench: dug along the crest of slopes, with the liner run into it and backfilled with compacted soil.
3. Deployment: panels unrolled down slopes, not across them, with ballast (sandbags) against wind. Avoid deploying in strong wind or rain.
4. Seaming: double-track hot wedge welds for panel seams, extrusion welds for patches, corners and pipe boots.
5. Seam testing: air-pressure testing of the channel between wedge-weld tracks (ASTM D5820), vacuum-box testing of extrusion welds (ASTM D5641), and destructive peel and shear samples checked against GRI-GM19.
6. Cover: place protection geotextile and cover soil promptly, with low-ground-pressure equipment and enough soil thickness under the tracks to avoid damaging the sheet.

Frequently asked questions

What is the difference between a geomembrane and a geotextile?

A geomembrane is an impermeable sheet that stops liquid. A geotextile is a permeable fabric that separates, filters, drains or cushions. They are often used together: a nonwoven geotextile under and over an HDPE liner protects it from puncture.

What thickness of geomembrane do I need?

It depends on the application and the regulator. MSW landfill base liners in India need 1.5 mm HDPE. Water ponds and canals are often lined with 500 micron to 1 mm sheet, going thicker where the subgrade is rough, the liner is exposed or the head of water is high.

Which standards apply to HDPE geomembranes in India?

IS 16352:2020 specifies HDPE geomembranes for lining in India, and HDPE geomembranes for lining are covered by a BIS quality control order. GRI-GM13 is the international reference specification, and most project specifications quote both.

How long does an HDPE geomembrane last?

Buried HDPE that meets GRI-GM13 is expected to last centuries at normal ground temperatures, based on GRI’s accelerated ageing work. Exposed sheet lasts decades rather than centuries, depending on sunlight, temperature and the antioxidant package.

See HDPE geomembrane on site in our Badarpur NTPC Eco Park, Delhi project, or browse more case studies.