Page 333 - Materials Chemistry, Second Edition

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304 Waste Management Practices: Municipal, Hazardous, and Industrial
10.4.12 GEOMEMBRANE LINER HANDLING AND PLACEMENT
The surface of the compacted soil liner must be smooth and sufficiently strong to provide continu-
ous support for the geomembrane liner. The soil surface must be relatively free of rocks, roots, and
excess water. EPA studies (U.S. EPA, 1988) show that nonangular stones present at the surface and
smaller than ¾ in. in diameter will not damage most geomembrane liners.
Geomembrane liners composed of PVC are commonly prefabricated into large panels, folded,
and shipped on pallets. The liners manufactured from HDPE and PP must not be folded and are
shipped to the site in rolls. Once delivered to the site, liners should be stored to avoid direct con-
tact with the ground surface. A protective surface such as a geotextile (see below) may be placed
over the ground, or the geomembrane liner rolls could be wrapped in plastic at the factory. The
stored geomembrane liner should also be protected from exposure to excessive heat, dust, and
water (U.S. EPA, 1994).
At the time of installation, the geomembrane liners are rolled out or spread out over the soil
liner with each sheet overlapping the adjacent sheets. The geomembrane liners are then seamed
together to create a single impermeable layer. A number of methods are available to create strong
seams including extrusion, fusion, chemical, and adhesive seams (Figure 10.6). Thermal seaming
is the most common method of attaching the sheets. It requires both proper weather conditions and
a clean surface on both membrane surfaces. If the surface of a membrane is wet, water can vapor-
ize and produce bubbles within the seam that reduces seam strength and may ultimately result in
leakage. Ambient temperature must also be considered during installation. Thermal seaming
should be performed when the ambient temperature is between 4.4 and 40°C (40 and 104° F).
Another practical concern in geomembrane liner seaming is the presence of dust; therefore, dust
control during the seaming process is critical (U.S. EPA, 1994). As geomembrane liner seaming is
a critical aspect in maintaining membrane integrity, a seam testing program should be established
for quality control.

Fillet type
Flat type
(a) Extrusion seams

Single hot air
Dual hot wedge
(b) Fusion seams

Chemical

(c) Chemical seam

Chemical adhesive Contact adhesive
(d) Adhesive seams

FIGURE 10.6 Seaming methods for landfill liners (U.S. EPA, 1994).