Case Study: Crawfish Hatchery Building Project in Bhutan

Ocean Non Wovens supplied and installed 7500 square meters of Ocean HDPE – 750 Micron liner for a crawfish hatchery in Bhutan. The liner holds the water in the hatchery tanks and ponds and keeps it separate from the surrounding soil, a standard approach in aquaculture construction.

Location: Bhutan
Product: Ocean HDPE – 750 Micron (0.75 mm)
Quantity: 7500 sq m
Scope: supply and installation

Why a hatchery needs a liner

A hatchery has to hold water at a set level and keep its quality stable for breeding and young stock. Unlined earthen ponds lose water to seepage, take up silt and organic matter from the soil, and can let hatchery waste water seep into the ground. A geomembrane liner solves all three:

• It stops seepage, so water levels stay steady and less make-up water is needed.
• It separates the water from soil contaminants and turbidity.
• It keeps hatchery effluent from soaking into the surrounding ground.

Why Ocean HDPE – 750 Micron

• Puncture and tear resistance: stones in the subgrade, tools and handling during harvests are the usual causes of liner damage in aquaculture. HDPE has high tensile and tear strength for its thickness.
• Chemical resistance: HDPE is largely inert and is not affected by the salts, feed residues and treatment chemicals found in hatchery water. It is widely used for fish and shrimp ponds.
• UV stability: UV exposure rises with altitude, which matters for exposed pond liners in Bhutan. HDPE geomembranes contain carbon black (typically 2–3%) and stabilisers to resist UV degradation on long-term exposure.
• Workable thickness: at 0.75 mm the sheet is light enough to carry and position on difficult sites, while still being weldable with standard fusion equipment.

Installation

1. Site preparation: the site was cleared of debris, sharp objects and other hazards that could puncture the liner, and levelled for even installation and proper water flow through the hatchery.
2. Liner deployment: the sheets were unrolled and positioned to cover the entire hatchery base, with planned overlaps between panels.
3. Seaming and testing: the Ocean HDPE sheets were joined by welding, and the installation was checked with pressure and water tests.

Site challenges

Terrain and access. Bhutan is mountainous, so getting rolls to site and laying them on uneven ground takes planning. A geomembrane follows the shape of the prepared subgrade, which makes it easier to fit to irregular sites than rigid concrete tanks.

Temperature swings. Bhutan’s climate ranges from subtropical in the southern foothills to cold in the higher valleys, and daily swings can be large. HDPE expands and contracts noticeably with temperature, so installers leave a little slack in the sheet during warm hours and anchor it in trenches at the crest. That stops the liner going taut and stressing the seams when it cools.

Effluent control. Hatchery water carries nutrients and waste. Because HDPE is impermeable, the liner keeps this water within the system until it is treated or discharged.

Outcome

The lined tanks and ponds give the hatchery a watertight base that holds water levels steady and keeps the water separate from the soil.

For aquaculture ponds, hatcheries or pond liners, call +91 84472 26007 or browse more case studies and our range of geosynthetics.