Why geotextile is mandatory under liner
HDPE geomembrane is thin relative to rock and angular subgrade—non-woven geotextile cushions the liner from puncture and stabilizes the interface. Petroseal geotextile (polypropylene or polyester non-woven) is specified under and sometimes over liner zones, behind riprap, and in toe drainage blankets on Suki Kinari and Diamer Bhasha–class deployments.
Skipping cushion geotextile to save cost is a common source of liner leaks discovered only after impoundment.
Mass and roll selection
| Mass (g/m²) | Typical role |
|---|---|
| 200 | Light separation, controlled subgrades |
| 300–400 | Standard cushion under HDPE on rocky subgrade |
| 600 | Heavy puncture resistance, aggressive fill |
Wide rolls (4m and 6m) speed deployment on large sites. Overlap seams per consultant specification—usually 300mm minimum on cushion layers.
Filtration and drainage blankets
Geotextile allows water passage while retaining fines in toe drains and filter zones behind riprap on hydraulic structures. It must be paired with appropriate graded fill—not used alone as a drain without hydraulic design.
QA on site
Store rolls off the ground, covered from UV until installation. Repair punctures in placed geotextile before liner deployment. Document overlap widths in the installation log for owner QA.
Read our HDPE geomembrane guide for full liner build-up. Contact 0321 8489737 for mass-grade recommendations on your subgrade report.