Case Study: Purulia Mega Projects – Raw Water Reservoir

For the Purulia Mega Projects-Raw Water Reservoir in West Bengal, Ocean Non Wovens supplied 17,000 square metres of Ocean HDPE Liner, 1mm thick. The liner seals the reservoir so the raw water it stores, for agriculture, industry and domestic supply, is not lost to seepage.

Purulia is one of the most drought-prone districts in West Bengal. It sits on the eastern edge of the Chota Nagpur plateau, where most of the year’s rain falls in a few monsoon months and runs off the undulating, lateritic ground quickly. Storing water through the dry season is the only way to have it when it is needed, and an unlined reservoir in these soils would lose much of what it holds.

Project overview

• Location: Purulia, West Bengal, India
• Product Supplied: Ocean HDPE Liner 1mm thickness
• Quantity: 17,000 Sqm
• Application: Raw water storage reservoir lining

The project stakeholders chose the Ocean HDPE Liner 1mm for its durability under harsh site conditions, its cost and its performance on similar reservoirs.

Why an HDPE liner

High-density polyethylene (HDPE) liners are now standard for lining raw water reservoirs. They stop seepage, protect the reservoir embankments from water moving through them, and cut water loss. The main reasons:

• Durability: HDPE resists chemical attack, UV radiation and temperature extremes, so it suits long-term water storage.
• Flexibility: The sheet follows the shape of the reservoir bed and slopes and stretches over minor settlement without cracking.
• Water quality: The liner keeps stored water separate from the surrounding soil, and HDPE is inert in water.
• Cost: Long life and low maintenance make it economical for large reservoirs.

A 1mm (1000 micron) sheet balances tensile strength and flexibility. It has a good margin against puncture and the stresses from a deep water column and harsh weather, while remaining practical to deploy and weld over a reservoir of this size.

Installation

Installation quality decides whether a lined reservoir holds water. A flaw in the liner means water loss and, behind an embankment, possible structural damage.

• Site preparation: The reservoir bed and slopes were prepared to a smooth, even surface to avoid punctures or tears. On stony or gravelly lateritic ground, a non woven geotextile cushion under the liner is the usual extra protection.
• Liner placement: The liner was rolled out to cover the whole reservoir area, following the contours of the site.
• Seaming: Panels were joined by thermal fusion welding to form one continuous barrier. On large reservoirs this is normally double-track hot-wedge welding for long seams, with extrusion welding for details and patches.
• Quality control: After installation the liner was tested by vacuum testing, air pressure testing of the seams and visual inspection.
• Anchoring: Liner edges on a reservoir are normally buried in an anchor trench at the crest of the slopes.

Site challenges

Temperature swings. Purulia has very hot summers and cool winters. HDPE expands and contracts with temperature, so the liner needs to be laid with the right amount of slack and welded at stable sheet temperatures. A 1mm sheet tolerates this movement without losing integrity.

Monsoon. Heavy monsoon rain fills the reservoir quickly and can soften the embankments. The impermeable liner keeps the stored water in and keeps it out of the embankment soil.

Variable soils. Soil types vary across the site. The liner’s flexibility and strength let it perform on each type of subgrade.

After installation

• Monitoring: Regular inspection after installation catches problems early, especially on exposed slopes and at anchor trenches. Ocean Non Wovens provides after-sales support, including inspections and maintenance guidance.
• Environment: Beyond saving water, the liner keeps the stored water from mixing with the soil around it.
• Community: The reservoir provides a reliable water supply that has improved agricultural productivity, supported local industries and improved quality of life for residents.

For reservoir, pond or canal lining, contact Ocean Non Wovens to discuss liner thickness and installation for your site, or see more water storage projects on the case studies page.