New landfills are designed with "cells" that are lined to prevent groundwater contamination. The liner system used in new cell construction will consist of low-permeability compacted clay soil. A 60-mil, high-density polyethylene (HDPE) plastic liner is installed over the soil liner to complete the composite liner system.
A blanket of geotextile fabric, composed of synthetic, felt-like fibers, is laid above the primary liner system, along with a geonet made of mesh-like plastic. Together, these provide drainage for leachate and prevent fine particles from clogging the leachate collection layer and promote removal of leachate from the liner surface.
Leachate collected by this layer is directed to a leachate collection piping system that diverts the leachate to the leachate collection sumps where leachate is removed with submerged pumps.
Strict guidelines that must be followed in constructing the liner system are summarized below:
- The qualified liner installation contractor must have certified personnel and equipment to perform the work. Qualifications of the personnel must be approved by TCEQ.
- Field seams are oriented parallel to slopes to reduce stress on the seams. Adjacent geomembrane panels will be overlapped to facilitate a strong, double seam. Peel tests are performed on all field seams to ensure strength and seam integrity.
- Final acceptance of the geosynthetic liner system is based on certification by an independent, licensed engineer and quality assurance consultant who certify that the geosynthetic materials have been properly installed.
- Following approval of a lined area by a quality assurance inspector, protective cover materials are placed.
- Liner installation/certification reports are submitted to the TCEQ for review and approval.
Typical Anatomy of a Landfill