Double-liner sealing systems protect groundwater at facilities for storing, filling and transferring (LAU) and for manufacturing, treating and using (HBV) water-hazardous substances. In these applications particularly aggressive substances could otherwise contaminate groundwater. A control (leak-monitoring) system is installed between two Carbofol® HDPE geomembranes, and Secutex® protective nonwovens safeguard the seal against mechanical damage. Typical facilities include tank farms, filling stations, chemical-industry plants and sealed industrial buildings.
Double-liner sealing systems are deployed wherever industrial facilities handle water-hazardous substances and require monitored groundwater protection.
Sealed, monitored containment beneath fuel and chemical storage
Groundwater protection under forecourts and dispensing areas
Containment for production and handling of aggressive substances
Sealed floors and areas where water-hazardous substances are handled
A double-liner system places a permanently monitored control zone between two Carbofol® HDPE geomembranes; Secutex nonwovens protect the seal from mechanical damage. The result is redundant sealing with the ability to detect, localise and contain a defect before any substance reaches the subgrade or groundwater.
Double-liner sealing systems for LAU/HBV facilities are designed and installed in accordance with German water-protection law and the relevant approvals. Naue provides engineering support and installation as a certified WHG specialist company.
Practical benefits:
An HDPE drainage grid between the two Carbofol® HDPE geomembranes maintains a permanent gap which is the monitoring zone. System integrity can be checked both electro-resistively and by vacuum testing, either continuously or periodically. The monitoring zone is usually divided into individual test fields, each with two connections (a suction line and a measurement line), so that a defect can be localised and its spread across the zone contained.
The vacuum method maintains a negative pressure in the control zone; a sudden drop in the vacuum signals a defect. Dividing the zone into test fields, each with a suction and a measurement line, allows the defect to be localised. The electro-resistive method places a special control geotextile in the control space, connected by a matrix of measuring points to an evaluation unit that maps the local electrical resistance of the nonwoven; a change in resistance triggers an alarm.
High-quality double-liner systems require appropriately dimensioned, long-term-durable, mechanically bonded protective nonwovens. The mass per unit of the Secutex® nonwoven selected depends on whether the subgrade or bedding layer is a low-gravel sand (gravel content below 30%) or coarser-grained soils. The nonwovens prevent mechanical damage to the Carbofol® membranes during installation and later operation.
Selection depends on the subgrade, the monitoring requirement and the substances handled. This matrix outlines the typical choices.
Key principle: the two sealing membranes contain the substance; the monitored control zone detects and localises any defect before groundwater is affected.
| Scenario | Recommended |
|---|---|
| Low-gravel sand subgrade (gravel < 30%) | Secutex® PP protective nonwoven, 400 g/m² |
| Coarser-grained/more angular subgrade | Secutex® PP protective nonwoven up to 1,200 g/m² (application-specific) |
| Continuous monitoring required | Electro-resistive control geotextile with a permanent evaluation unit |
| Periodic integrity checks | Vacuum monitoring via test fields (suction and measurement lines) |
Protected, chemical resistant seal
Carbofol® HDPE withstands aggressive, water-hazardous substances. Secutex® nonwovens prevent mechanical damage during installation and operation.
Redundant sealing
Two Carbofol® HDPE membranes; a defect in one does not defeat containment.
Early leak detection
The monitored control zone signals a defect before groundwater is affected. Division into test fields pinpoints and contains any defect.
They protect groundwater at LAU (storing, filling, transferring) and HBV (manufacturing, treating, using) facilities that handle water-hazardous substance. Respective industrial containment application areas are for example tank farms, filling stations, chemical-industry plants and sealed industrial buildings, where particularly aggressive substances could contaminate groundwater.
Two Carbofol® HDPE geomembranes, an HDPE drainage grid (and, for the electro-resistive method, a control geotextile) forming the monitored zone, and Secutex® PP protective nonwovens. No geosynthetic clay liner is used in this application.
For a low-gravel sand subgrade (gravel content below 30%), a Secutex® PP nonwoven of 400 g/m² is sufficient. For coarser-grained soils, mechanically bonded PP Secutex® nonwovens of up to 1,200 g/m² are used, selected per application.
Yes. The system can be monitored continuously or periodically. The electro-resistive method uses a control geotextile and a permanent evaluation unit; the vacuum method uses test fields with suction and measurement lines.
Between the two Carbofol® membranes, an HDPE drainage grid keeps a control zone permanently open. System integrity is monitored either electro-resistively or by vacuum, continuously or periodically. A sudden drop in vacuum, or a change in electrical resistance, signals a defect.
The monitoring zone is divided into individual test fields. With the vacuum method each field has a suction and a measurement line; with the electro-resistive method a matrix of measuring points maps the control geotextile. Either way, a defect can be pinpointed and its spread within the zone contained.
A single seal cannot warn of a defect before contamination occurs. Two membranes provide redundancy, and the monitored gap between them allows a defect to be detected and localised early, before any substance reaches the subgrade or groundwater. Please contact us for support in your system selection process.
In Germany, the WHG (Water Resources Act) and the AwSV (ordinance on installations handling water-hazardous substances) govern LAU/HBV facilities. Sealing systems require DIBt approval, the substances handled are classified by water hazard class (WGK), and installation is carried out by a certified WHG specialist company like Naue.
Carbofol® HDPE geomembranes offer high chemical resistance suited to aggressive, water-hazardous substances. Project-specific chemical compatibility is confirmed by Naue for the substances handled.
Yes. Naue is a certified WHG specialist company and provides engineering support, seam welding and quality assurance (including vacuum and pressure testing of welds) and on-site installation.
Naue Secutex® is a mechanically bonded nonwoven geotextile for separation, filtration and protection in roads, railways and hydraulic engineering projects.
