Water Storage Pond Lining in Port Blair: 1 mm HDPE Liner over 400 GSM PET Geotextile

Port Blair (now Sri Vijaya Puram), in the Andaman and Nicobar Islands, gets heavy monsoon rain, yet much of it runs straight off into the sea. Through the dry months the islands depend on stored water. A storage pond only helps if it holds what it collects, so the lining has to be watertight and built to last.

For this water storage pond, Ocean Non Wovens supplied two products that work as one lining system: 13,500 sq m of 400 GSM PET non-woven geotextile as the protection and cushion layer, and 13,500 sq m of 1000 micron (1 mm) HDPE liner over it as the impermeable barrier.

Project snapshot

Why the pond needed a geosynthetic lining

Traditional pond linings struggle to stay watertight, especially on difficult ground:

• Clay cracks as it dries and still seeps even when well compacted.
• Concrete and masonry are rigid, so they crack at joints and under settlement.
• Every crack is a leak that is hard to trace and costly to repair.

An HDPE geomembrane replaces all of that with a continuous, effectively impermeable sheet that installs quickly over a prepared surface. Because a liner is only as safe as the ground beneath it, it is paired with a protective geotextile.

The island setting added its own demands:

• Remoteness: materials are shipped in and repairs are slow and expensive, so reliability comes first.
• Heavy monsoon rainfall: the pond fills fast and the surrounding ground stays saturated.
• Seismic activity: the Andaman region is one of the most seismically active parts of India, so the lining must tolerate ground movement.
• Coastal exposure: salt-laden air calls for a material that does not corrode or degrade chemically.
• Uneven subgrade: stones and sharp fragments put the liner at risk of puncture.
• Intense sun: strong ultraviolet radiation attacks any uncovered liner.

How the geotextile and HDPE liner work together

Under the weight of stored water, stones, roots and sharp edges in the subgrade press into the liner from below. Even a 1000 micron sheet can be pierced by an angular stone under a few metres of water. The 400 GSM needle-punched geotextile spreads those point loads over a wider area, so the liner stays intact.

Ocean Non Wovens makes both products, so it supplies the liner and the geotextile as a matched pair, with grades chosen for the ponding depth and the subgrade.

Why a 1000 micron liner and 400 GSM geotextile

This project used thicker, heavier grades than a typical shallow farm pond:

• Remote location: on an island a tougher lining lowers the risk of a failure and a repair callout.
• Greater durability: a 1000 micron liner has higher puncture and tear resistance than thinner grades and more margin against long-term stress cracking.
• Stronger protection: a 400 GSM geotextile is a heavy cushion against a rough subgrade.
• Demanding environment: heavy rainfall, coastal air and seismic activity all favour a tougher, more forgiving lining.

Product specifications

Ocean HDPE Liner, 1000 micron

Ocean Non-Woven Geotextile (PET), 400 GSM

HDPE liner vs clay or concrete lining

Shipping thousands of tonnes of clay or concrete to an island is costly and slow. A geosynthetic lining arrives as compact rolls, and a pond that does not lose water to seepage keeps its monsoon catch through the dry season.

The technical basis

Impermeability. HDPE is dense enough that seepage through an intact, properly welded sheet is negligible. Leakage in practice comes from holes and bad seams, which is why the cushion layer and seam testing matter.

Puncture protection. The heavy geotextile absorbs concentrated stresses from the subgrade, a property tied to its puncture resistance (ASTM D6241) and grab tensile strength (ASTM D4632).

Hydrostatic containment. The anchored liner resists the pressure of the stored water column. HDPE has a high elongation at break, so the sheet can take settlement and seismic movement without tearing, provided it is not pulled taut at installation.

Turning many panels into one continuous barrier depends on sound seaming. Double hot-wedge seams are checked by air-pressure testing of the channel between the two welds (ASTM D5820), and extrusion welds at patches and details by vacuum box (ASTM D5641).

Installation sequence

1. Prepare the subgrade: trim, compact and clear the bed and slopes of stones and sharp debris.
2. Lay the geotextile: roll out the 400 GSM PET fabric across the bed and slopes with the specified overlaps.
3. Deploy the liner: roll out the 1000 micron HDPE panels over the geotextile, positioned to minimise field seams.
4. Weld and test: join the panels by hot-wedge and extrusion welding, then test every seam.
5. Anchor and secure: fix the lining in a perimeter anchor trench, ballast it against wind, and leave slack for thermal and seismic movement.

The usual causes of failure are sharp points left in a poorly prepared subgrade, an under-lapped or missing geotextile, weak or untested welds, and a liner left uncovered and unballasted for too long during construction.

Long-term performance

• UV resistance: the liner is carbon-black stabilised against strong island sun.
• Stress-crack resistance: tested to ASTM D5397, it resists slow crack growth, the usual end-of-life mechanism for polyethylene sheet.
• Chemical resistance: HDPE is not affected by the salts and coastal chemistry the pond is exposed to.
• Cyclic durability: it holds up under repeated wetting, drying, thermal cycles and ground movement.
• Low maintenance: with no moving parts, the system needs only periodic inspection of exposed slopes and anchor trenches.

The same geotextile and HDPE liner combination is used for drinking and raw water reservoirs, rainwater harvesting structures, irrigation and farm ponds, canals, aquaculture ponds, effluent and sewage lagoons, industrial process ponds and landfill barrier layers.

Frequently asked questions

What liner thickness was used for the Port Blair pond?

A 1000 micron (1 mm) HDPE liner, laid over a 400 GSM PET non-woven geotextile. Both products covered 13,500 sq m.

Why put a geotextile under an HDPE pond liner?

The geotextile cushions the liner against stones and sharp points in the subgrade and spreads the load of the stored water, so the liner is not punctured.

Is an HDPE liner better than clay or concrete for a pond?

For seepage control, yes. Clay seeps and cracks as it dries, and concrete cracks at joints and under settlement. A welded HDPE liner is effectively watertight and flexes with ground movement.

Why use a thicker liner on an island project?

Repairs on an island are slow and expensive, and the Andaman region is highly seismic. A 1000 micron liner gives more puncture and tear resistance than thinner grades, which lowers the risk of a failure that is hard to reach.

For the site steps that sit behind a two-layer lining like this, see our guide to installing a geotextile liner under a pond liner: grade selection on puncture, laps and run-outs, base preparation and common mistakes.

Partner with Ocean Non Wovens

Ocean Non Wovens supplied 13,500 sq m each of geotextile and HDPE liner to this Port Blair pond. The company manufactures HDPE liners, non-woven and woven geotextiles, geocells, geogrids and geobags in India, tested to Indian and international specifications. Its materials go into water resources and environmental works, irrigation and pond lining, highways, railways, industrial developments, airports and defence infrastructure across India and its islands.

For pond and reservoir lining, seepage control or containment, Ocean Non Wovens can recommend and supply liner and geotextile grades to suit your site conditions. Talk to the Ocean team about your next project.