When roads are built in water catchment and protection areas, the German guideline RiStWag (“Richtlinien für bautechnische Maßnahmen an Straßen in Wasserschutzgebieten/Wassergewinnungsgebieten”) requires the subgrade to be sealed and targeted construction measures to be taken to protect groundwater. Naue provides the complete system: Bentofix® geosynthetic clay liners (or Carbofol® HDPE geomembranes) as the sealing element, Secutex® protective nonwovens, Secugrid® geogrids for slope stability and Secumat® mats for surface erosion control. Outside Germany, equivalent national regulations for roads in water protection areas apply. The same engineering approach and products are used internationally.
These systems are used wherever roads in water protection or catchment areas must seal the subgrade and protect groundwater.
Sealing road subgrades in protection/catchment areas.
Sealed and stabilised slopes on new roads
Containing polluted runoff along the carriageway
Sealing and surface-erosion control on cuttings
RiStWag requires the road subgrade to be sealed and targeted measures to be taken to protect groundwater. Naue supplies the sealing element and the associated protection, slope-stability and erosion-control layers as one coordinated system.
Seal: Bentofix® GCL or Carbofol® geomembrane
As an alternative to the usual compacted 40 cm mineral seal, the approx. 10 mm needle-punched Bentofix® geosynthetic clay liner with highly swellable sodium bentonite is used; its robust cover and carrier geotextiles are dimensioned to resist installation damage. The encapsulating geosynthetics are usually polypropylene (PP) and therefore sufficiently resistant to conventional chemicals; for special cases where higher chemical aggressiveness must be expected, a coated bentonite mat (Bentofix® X) is used. Alternatively, Carbofol® HDPE geomembranes can be installed.
Stabilise slopes: Secugrid® geogrids
With Bentofix®, slope inclinations steeper than 1:2.5 are achievable depending on the prevailing soil conditions and slope lengths. For unfavourable soil conditions or steeper slopes, stability is ensured by an additionally installed Secugrid® geogrid.
Protect: Secutex® nonwovens
For Bentofix® GCLs, the encapsulating geosynthetics protect the bentonite and provide robustness for site handling. For Carbofol® geomembranes, proper and professional installation is especially important: depending on requirements, mechanically bonded protective nonwovens such as Secutex® (PP) are placed above and, if necessary, below the geomembrane. Secutex® PP nonwovens are used in construction measures carried out according to RiStWag.
Control erosion: Secumat® mats
The Secumat® erosion control mat retains the soil within its three-dimensional random-mesh structure against flowing surface water. Secumat® is laid directly on the slope and filled with soil; the roots of the vegetation grow around the Secumat® mesh and anchor firmly, protecting the slope surface from erosion.
Selection depends on chemical exposure, slope geometry and the sealing detail required. This matrix summarises the typical choices.
| Scenario | Recommended |
|---|---|
| Standard chemical exposure | Bentofix® GCL (PP-encapsulated) or Carbofol® HDPE geomembrane |
| Higher chemical aggressiveness | Bentofix® X (coated GCL) |
| Continuous welded seal/complex layouts | Carbofol® HDPE geomembrane with Secutex® protection above and, if needed, below |
| Steep slopes (> 1:2.5)/poor ground | Add a Secugrid® geogrid for slope stability |
| Slope-surface erosion/revegetation | Secumat® erosion control mat, laid on the slope and filled with soil |
Practical benefits:
Compliant sealing
Geosynthetic barrier solutions seal the road subgrade in line with RiStWag and national equivalents: Bentofix® for conventional chemicals, Bentofix® X for higher aggressiveness, and weldable Carbofol® HDPE as an alternative.
Thin, fast seal
An approx. 10 mm GCL replaces the usual 40 cm compacted mineral seal, reducing material and installation effort.
Complete system
Sealing, protection, slope stability and erosion control from one supplier, specified together.
RiStWag is a German FGSV guideline (“Richtlinien für bautechnische Maßnahmen an Straßen in Wasserschutzgebieten/Wassergewinnungsgebieten”). When roads are built in water protection or catchment areas, it requires the subgrade to be sealed and targeted construction measures to be taken to protect groundwater. Outside Germany, equivalent national regulations apply.
Bentofix® and Bentofix® X geosynthetic clay liners and Carbofol® HDPE geomembranes as the sealing element, Secutex® protective nonwovens, Secugrid® geogrids for slope stability and Secumat® mats for surface erosion control.
Yes. An approx. 10 mm needle-punched Bentofix® GCL with sodium bentonite replaces the usual 40 cm compacted mineral seal.
The standard Bentofix® is sufficiently resistant to conventional chemicals. Where higher chemical aggressiveness must be expected, the coated bentonite mat Bentofix® X is used. For product details see the Naue geosynthetic barrier portolio.
Carbofol® HDPE geomembrane is an alternative sealing element that is easy to lay and, thanks to a favourable melt index, weldable into a continuous seal. It requires Secutex® protective nonwovens above and, if necessary, below the geomembrane.
With Bentofix®, slope inclinations steeper than 1:2.5 are achievable depending on soil conditions and slope length. For steeper slopes or unfavourable ground, a Secugrid® geogrid ensures stability.
A Secumat® erosion control mat is laid directly on the slope and filled with soil; vegetation roots grow around its three-dimensional mesh and anchor firmly, protecting the surface from erosion.
RiStWag is a German framework, but the engineering approach of sealing the road subgrade to protect groundwater in water protection areas applies internationally. Naue aligns designs with the applicable national regulations and supplies the appropriate products.
Carbofol® and Bentofix® carry CE marking and, in Germany, hold the relevant approvals for these applications. Naue provides full product documentation for inclusion in specifications and regulatory submissions. Please contact us if we can give you advice for your project.
Yes. Naue provides engineering support (digitally in the Naue Portal and personally), seam welding and quality assurance, and installation. In Germany, Naue is a certified WHG specialist company.
RiStWag defines the sealing requirement for roads in water protection areas; Naue supplies and installs the sealing element and the associated layers. Outside Germany, equivalent national regulations apply.
Frameworks:
Products:
Naue Bentofix® is a geosynthetic clay liner (GCL) for waterproofing in landfill engineering, groundwater protection and hydraulic applications.
Naue Bentofix® X geosynthetic clay liner is a multicomponent PE-coated GCL for landfill, waterproofing and slope sealing.
Naue Carbofol® is a HDPE liner for landfill sealing, mining containment, and groundwater protection.
Naue Secutex® is a mechanically bonded nonwoven geotextile for separation, filtration and protection in roads, railways and hydraulic engineering projects.
Naue Secugrid® geogrid stabilises and reinforces roads, embankments, working platforms, slopes and walls.
Naue Secumat® is an erosion control mat for the protection of slopes, channels and embankments.
