Landfills are
designed with "cells" that are lined to prevent
groundwater contamination. The liner consists of a two-foot
layer of low-permeability, re-compacted clay soil. Over
this layer, a 60-mil, high-density polyethelene (HDPE) secondary
plastic liner is installed to cover the entire bottom and
sides of the landfill cell. This plastic liner, which is
chemical resistant to corrosion and damage, is then welded
together and tested to ensure a continuous seal in accordance
with regulatory requirements.
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 prevent fine clay particles from clogging the leachate collection layer and promote removal of leachate from the liner surface.
Strict construction guidelines must be followed in constructing the liner system, which are summarized below:
- The qualified liner installation contractor must have certified personnel and equipment to perform the work.
- Personnel performing field liner seaming are qualified by experience and by passing field seaming tests.
- 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 that certifies 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.
