Case Study: Ocean HDPE Liner Installation for Thermal Power Project in Singrauli

For a thermal power project in Singrauli, Madhya Pradesh, Ocean Non Wovens supplied and installed 20,000 square metres of Ocean HDPE Liner-100 Micron. The liner was used for seepage control and waste containment, to keep ash and other by-products from contaminating the soil and groundwater around the plant.

The project

• Sector: Thermal power
• Location: Singrauli, Madhya Pradesh
• Product: Ocean HDPE Liner-100 Micron
• Quantity: 20,000 Sqm
• Scope: Supply and installation

Singrauli, often called India’s “energy capital”, has a cluster of large coal-fired power stations. Burning coal leaves fly ash and bottom ash, usually stored in ash ponds and dykes. Water draining from ash can carry dissolved salts and trace elements, so containment has to stop it seeping into the ground.

Where HDPE liners are used in thermal power plants

• Ash ponds and containment: An HDPE liner forms an impermeable layer under ash ponds, so leachate cannot reach the surrounding soil and water bodies. Power plants produce ash in very large quantities, which makes containment a continuous requirement.
• Water storage and sludge ponds: Liners prevent seepage losses from raw water and process ponds, and keep sludge from contaminating groundwater.
• Durability: Power plants run for decades. HDPE does not rot or corrode and needs little maintenance once installed.
• Chemical and UV resistance: Containment liners at a plant can meet chemicals, hydrocarbons and strong sun. HDPE resists most of these, and carbon black in the resin protects it from UV.

The liner

The Ocean HDPE Liner-100 Micron was chosen for the Singrauli project for these properties:

• Tensile strength: Polyethylene of geomembrane grade gives the sheet the strength to carry the load of the contained material.
• Flexibility: The liner stretches with ground movement and with shifts in the contained material, instead of cracking like a rigid lining.
• Chemical resistance: HDPE resists the chemicals found in fly ash and sludge.
• UV stability: Liners at thermal plants are often exposed to sun for long periods. The liner has been tested for UV resistance.

Installation

Site preparation. The site was cleared of debris and levelled to give the liner a smooth bed, with sharp objects and uneven patches removed.

Deployment and welding. The 20,000 Sqm of liner was laid across the containment areas and the seams were fused by welding, including extrusion welding.

Quality control and testing. Each stage was checked. Vacuum testing, air pressure testing and destructive testing on selected samples were used to verify seam integrity. In standard practice, air pressure testing applies to double-track wedge seams (ASTM D5820), vacuum box testing to extrusion welds and patches (ASTM D5641), and destructive peel and shear tests to seam samples cut from the liner (ASTM D6392).

Environmental compliance. The containment system was designed to stop pollutants leaching into the surroundings, and installation followed the applicable environmental guidelines.

Site challenges

• Thermal movement: HDPE expands and contracts noticeably with temperature. Singrauli has very hot summers and seasonal monsoon rain, so the liner was laid with enough slack to accommodate temperature changes without being stressed.
• Heavy equipment: Industrial sites have machinery working near the liner. Protective layers were added where heavy equipment operated often, to prevent accidental punctures.
• Weather: The liner has to keep working through sun, heat and rain. UV stabilisation and flexibility are what let HDPE cope with these conditions.

Outcome

On completion, the plant had a containment system for fly ash and other waste materials that reduces the risk of soil and groundwater contamination. Ocean Non Wovens reports that the liner has performed well since installation in durability and leak prevention.

Ocean Non Wovens supplies HDPE liners and other geosynthetics for thermal power plants, landfill sites and industrial projects, with installation. Contact the team to discuss liner thickness and containment design for your site, or see more case studies.