Landfill Project At Dibrugarh, Assam – Case Study

Environmental / landfills

Product: HDPE Geomembrane

For an engineered municipal landfill in Dibrugarh District, Assam, Ocean Global supplied, installed and welded 18200 sq m of 1.5 mm HDPE Geomembrane across the base and slopes of the landfill cell.

Problem

Solid waste management is one of the core services of the municipal authority. Its Conservancy Department collects biodegradable waste from households every day, and its Solid Waste Management Department handles secondary storage, transport, processing and final disposal.

Dibrugarh district lies in eastern Assam and covers 3381 square kilometres. It is bordered by Dhemaji district and part of Lakhimpur district to the north, Sivasagar district and Arunachal Pradesh to the south, Tinsukia district to the east and Sivasagar district to the west.

Dibrugarh town has no sewerage network, and much of the population lacks proper sanitation. Waste goes to individual septic tanks or straight into drains and water bodies, contaminating the town’s water sources. Groundwater in the densely populated areas of the Dibrugarh Municipal Board (DMB), particularly Naharkhatia, has been found to be contaminated, and poorly managed solid waste has led to disease.

Given the environmental hazards of unregulated dumping, the municipal authority chose a remote site in Dibrugarh District for a secure, engineered landfill.

Solution

An HDPE geomembrane is the standard anti-seepage barrier for landfills. It is made from polyethylene resin (often a medium-density grade) compounded with carbon black, giving a finished sheet density of at least 0.94 g/cm3. It comes in two surfaces: smooth, for flat bases, and textured, whose rough surface gives much higher friction against soil and geotextiles and is used on slopes so the layers above do not slide.

In a single-liner municipal landfill, the base barrier system usually consists of a composite liner (an HDPE geomembrane over either a geosynthetic clay liner or a compacted clay liner), a protective layer above it, and a gravel leachate drainage layer on top. The composite liner is the main barrier against leachate reaching surface water or groundwater: the geomembrane stops flow, and the clay layer limits leakage through any defect.

HDPE geomembrane resists leachate chemicals and environmental stress cracking, has very low permeability, carries carbon black for UV resistance, and stays tough at low temperatures. The same properties make it the usual liner and cover for biogas digesters, sludge and sewage treatment facilities, and manure evaporation ponds.

The landfill’s capacity called for 18200 sq m of 1.5 mm HDPE Geomembrane. Ocean Global’s scope covered delivery, installation and welding of the 1.5mm thick Geomembrane on the bottom and slopes. The geomembrane is 97.5 percent polyethylene and 2.5 percent carbon black, resists environmental stress cracking, and its UV resistance suits both exposed and covered use.

Physical and mechanical properties of the membrane supplied:

• Density: 0.94 g/cm3
• Strength at break: 43 N/mm
• Elongation at break: 700%
• Tear resistance: 187 N
• Puncture resistance: 530 N
• Roll size: 7m X 140m

These values meet or exceed the GRI-GM13 minimums for 1.5 mm smooth HDPE (density 0.940 g/cm3, 40 N/mm break strength, 700% break elongation, 187 N tear, 480 N puncture), and the carbon black content sits within GM13’s 2.0–3.0% range.

The construction process

The client specified the layers needed to stop leachate escaping through the landfill base: a 1000mm embankment, the 1.5 mm thick Geomembrane, 300mm of coarser material and 2 mm drainage aggregate. The top edge of the Geomembrane was fixed with a layer of cement concrete, with a 3m lap.

A network of pipes and two sumps collects leachate and landfill gas for disposal. A surface drainage system built across the landfill keeps rainwater out of the waste, which also reduces the volume of leachate produced.

For a similar project, see the Avaragolla solid waste management case study.