A landfill intermediate sealing system is an engineered sealing system installed between two overlapping (stacked) waste bodies. It acts at the same time as the surface (closure) seal of the completed cell below and as the base seal of the new cell above, allowing a landfill to be raised or extended laterally - known as a piggyback expansion or landfill-on-landfill. Because it must satisfy both surface-seal and base-seal requirements, it comprises a sealing layer with a mineral drainage layer above it and, where the old waste generates gas, a degassing layer below it. Bentofix® geosynthetic clay liners (GCLs) and Carbofol® HDPE geomembranes form the barrier; geogrids reinforce the settling old waste where its bearing capacity is insufficient; and geotextiles protect and filter the system.
Naue geosynthetic intermediate systems are used wherever landfill cells must be separated, stacked or extended while maintaining compliant containment and structural stability.
Extension of landfill capacity through vertical (piggyback) or lateral expansion by abutting a new cell.
Compliant barrier between neighbouring cells of differing landfill classification.
Phased landfill construction with intermediate seals between operational lifts.
Secugrid® geogrid to stabilise low-bearing old waste before new cell construction.
Intermediate seals are installed on soft, uneven and settling old-waste surfaces, often on inclined faces and under tight operational schedules while the landfill remains active. Bentofix GCLs and Carbofol geomembranes are engineered for these conditions and, where the old waste lacks bearing capacity, Secugrid geogrids provide the reinforcement needed to carry the new cell.
Intermediate seals are not explicitly codified in landfill legislation. Under GDA E 2-37 they must satisfy both the surface-seal requirements for the old body and the base-seal requirements for the new cell (DepV, LAGA-BQS); where these compete, the stricter governs. Because the old waste is a yielding, settling support, Eurocode 7 stability checks – sliding in the layer interfaces, overall (slope) stability and spreading safety (geotechnical category 2, DIN 4084) - together with settlement prognosis and, where required, EBGEO-based Secugrid® reinforcement design are essential. Naue provides barrier specification, slope-stability and settlement analysis and reinforcement design.
Practical advantages:
An intermediate seal has to do two jobs at once: close the cell below and form the base seal for the cell above. Depending on the waste classes, the bearing capacity of the old waste, gas generation and slope, it combines a barrier, structural reinforcement, a protection/filter layer, a mineral drainage layer above the seal and – where needed - a degassing layer below it.
Key principle: The GCL and geomembrane form the separating barrier. Secugrid® reinforcement carries the new cell over settling waste. Secutex® protects the barrier and filters the drainage layer. A mineral drainage layer above the seal removes the upper cell's leachate; where the old waste generates gas, a degassing layer sits below the seal. The design must meet both capping- and base-seal requirements, with the stricter governing (GDA E 2-37).
Core benefit: a thin, flexible barrier that replaces a thick mineral intermediate seal.
Core benefit: functional drainage, a protected barrier and controlled gas - acting as the base seal for the new cell.
The correct specification depends on the waste classes involved, the bearing capacity of the old waste, gas generation, slope geometry and the governing regulatory requirements (both surface- and base-seal; stricter governs). Use the decision table below as an engineering guide.
| Criterion | Site condition | Bentofix® GCL | Carbofol® HDPE | Composite and Secugrid® |
|---|---|---|---|---|
| Waste classes | Same class, both cells | Possible (single barrier) | Possible (single barrier) | Preferred for full separation |
| Waste classes | Differing/DK II–III | Not sufficient alone | Not sufficient alone | Required (composite seal) |
| Bearing capacity | Old waste stable | Barrier only | Barrier only | Barrier only |
| Bearing capacity | Soft/settling old waste | Add Secugrid® | Add Secugrid® | Composite + Secugrid® reinforcement |
| Gas from old waste | Gas generation present | Add degassing layer below | Add degassing layer below | Degassing layer below the seal |
| Slope gradient | Steeper than 1:3 (to 1:2) | Needle-punched GCL | Textured GM | Composite - verify interface friction |
| Regulatory basis | Both surface and base (Germany) | LAGA-BQS mineral component | BAM-approved geomembrane | Full compliance (stricter governs) |
| Leachate (upper cell) | Base-seal drainage | Mineral drainage above seal | Mineral drainage above seal | Mineral drainage and Secutex® filter |
Recover valuable airspace
Thin geosynthetic seal replaces a thick mineral intermediate seal, opening up revenue-generating airspace and extending site life within the same footprint.
Build safely on settling waste
Secugrid® geogrid reinforcement stabilises the old waste body and distributes loads (GDA E 2-37), allowing vertical (piggyback) or lateral expansion where mineral solutions would be impractical. Flexible Bentofix® GCL and Carbofol® geomembrane accommodate differential settlement without loss of barrier integrity; specified to both surface- and base-seal.
Faster, simpler installation
GCL panels need no welding; geomembranes are hot-wedge or extrusion welded; geogrids and geotextiles roll out with standard plant on the active site.
Single-source engineering
Barrier, reinforcement, protection and filtration from one supplier, with Naue design support, slope-stability and settlement verification (Eurocode 7, geotechnical category 2), reducing interfaces.
A landfill intermediate sealing system is an engineered sealing system installed between two overlapping (stacked) waste bodies. It serves at the same time as the surface (closure) seal of the completed cell below and as the base seal of the new cell above. This allows a landfill to be raised vertically (a piggyback expansion, or landfill-on-landfill) or extended laterally while separating the two waste bodies.
An intermediate seal is required when an existing landfill body is extended and at least partly overtipped while the base sealing of the old body is missing or insufficient – for example a missing base drainage, or neighbouring cells of different landfill classes. The intermediate seal then closes the lower cell and forms the base seal for the next.
Bentofix® GCL and Carbofol® HDPE geomembrane form the sealing (barrier) component – as a combination seal for higher landfill classes. Secugrid® geogrids reinforce and stabilise the old waste where its bearing capacity is insufficient. Secutex® geotextiles protect the geomembrane and filter the drainage layer, and a mineral drainage layer above the seal collects the upper cell's leachate.
Intermediate seals are not explicitly codified in landfill legislation. Under the GDA recommendation E 2-37 they must satisfy both the surface-seal requirements for the old body and the base-seal requirements for the new cell (DepV, LAGA-BQS); where these compete, the stricter applies. Geomembranes and protection layers follow the relevant BAM approval directives. Naue supports project- and jurisdiction-specific compliance.
A geosynthetic barrier is significantly easier and faster to install and takes up far less landfill space than a conventional mineral seal. Its flexibility adapts to site-specific conditions and accepts far greater strain during settlement of the yielding old waste. Because the layers are thin, they open up additional revenue-generating airspace and require far fewer truckloads than heavy aggregates.
The old waste is a yielding support, so long-term deformation is expected. Bentofix® GCLs self-seal minor damage and Carbofol® geomembranes remain flexible, so the barrier accommodates differential settlement. Settlement is predicted and monitored (Eurocode 7, geotechnical category 2), the system slope is over-built to preserve minimum drainage gradients, and Secugrid® reinforcement is added where stability requires it.
Where the underlying old waste generates gas through biological or chemical activity, a degassing (gas venting) layer is installed below the seal, in line with GDA E 2-37. This captures the gas and prevents pressure building up beneath the barrier, which could otherwise compromise the seal.
Yes. A combination seal of Carbofol® geomembrane over a Bentofix® GCL / mineral component, specified to the stricter of the surface- and base-seal requirements, provides the compliant separation required between cells of differing landfill classification.
No. Secugrid® geogrid reinforcement is used only where the old waste body does not provide enough bearing capacity or stability to support construction of the new cell. Where it is used, it also enables a more efficient, space-saving expansion design (GDA E 2-37).
Because the intermediate seal also acts as the base seal for the upper cell, leachate is collected in a mineral drainage layer (typically 0.3–0.5 m) above the seal. A Secutex® filter/separation geotextile is placed on the drainage layer to keep it functional over the service life.
Yes. Carbofol® HDPE geomembranes are BAM-approved for landfill use. Bentofix® GCLs hold LAGA certificates of suitability for German Landfill Classes I and II. Products conform to the relevant European standards, including EN 13257 and EN 13493.
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