An intermediate seal separates adjacent landfill cells
An intermediate seal is required if a new storage cell is raised or extended laterally. It is used when the landfill, to be abutted, does not have a sufficient seal to serve as base or an appropriate fill due to differing landfill classifications between the neighbouring cells. Thus, the intermediate seal can serve upper or closure layer of one cell and simultaneously, the base seal for the next.
Intermediate seals are not clearly described in most landfill regulations, so permitting authorities often call for typical base liner requirements. Historically, zoning decisions in municipal solid waste landfills have been issued in which the intermediate sealing should be constructed with the current state of the art barriers, e.g. with an approved geosynthetic clay liner (GCL) serving in place of a traditional mineral seal in combination with an approved geomembrane.
The advantages of this approach are clear: the geosynthetic barrier system is signifi cantly easier to install and takes up less landfill space than a conventional mineral seal (e.g., conventional compacted clay or largescale ground improvement methods). Furthermore, the flexibility of geosynthetic barriers enables them to adapt to the sitespecific conditions and far greater strain acceptance in settlement. Geosynthetics save considerable time and money here, reduce the need for soil and aggregate harvesting and disturbance and greatly reduce transport cost for site materials (as geosynthetics require far fewer truckloads than heavy aggregates). Also, geosynthetic layers, in being substantially thinner, open up revenue-generating airspace for a landfill.
Where the old waste cell does not provide enough stability to support the new cells construction, geogrid reinforcement may be required. This approach may also create a more efficient, spacesaving design, such as outlined in national regulations.