Geosynthetics April/May 2020 - 34

CSPE performance and history in long-term potable water storage applications

FIGURE 2 Metropolitan Water District of
Southern California Skinner Reservoir cover
installed in 2010

supplied into the market as a geomembrane, floating cover or single-ply roofing
material. A good portion of this material,
as reported by the main CSPE producer,
is still in service.

Properties of CSPE
CSPE has many advantages over other
commonly used polymers such as polyvinyl chloride (PVC), polyolefins and ketone
ethylene ester (KEE) resin technology.
One primary difference is that CSPE is
manufactured as a thermoplastic material
that will vulcanize over time, becoming a
thermoset material capable of surviving
thermally stressful and high-temperature
environments and ultraviolet (UV) exposure. When formulated and calendared
into a lining-grade material, it provides
outstanding UV resistance and weathering
properties allowing it to be used for longterm exposed containment applications.
In standard exposed applications, it demonstrates slow reduction of its mechanical
and endurance properties.
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The material's unique cross-linking
properties provide very good overall
resistances to several chemicals used as
disinfectants in municipal water treatment. These include chlorine, sodium
hypochlorite and chloramines. In water
treatment these three main chemicals
often act as accelerators, attacking and
breaking down the antioxidant packages
of a number of geomembrane types. This
can result in environmental stress cracking and premature material failure (Mills
2011). Since plasticizers are not used in
the formulation of CSPE geomembranes,
there are no issues related to plasticizers, such as leaching out and causing
embrittlement/cracking of plasticized
liners. Its inherent low coefficient of thermal expansion and contraction provides
excellent dimensional stability and layflat characteristics. CSPE also has a very
low thermal expansion coefficient compared to that of rigid membranes such as
high-density polyethylene (HDPE), and
so expansion and contraction problems
caused by temperature changes are virtually nonexistent. Elasticity is important in
liners because of the settling that occurs
after reservoirs or impoundments are
filled (Scheirs 2009).
CSPE's synthetic rubber properties
also provide it with a unique combination of flexibility and durability. In
geomembrane and floating cover applications, CSPE is typically factory fabricated. Fabricated geomembranes are
lining materials that are flexible enough
for panels to be joined in a factory environment, creating large prefabricated
panels of material that can be folded,
rolled and transported efficiently to a
containment project site. From there
these large prefabricated panels are
unrolled into position and field welded
on-site. Factory fabrication can significantly reduce the amount of field welding required, which reduces installation time and construction costs. It also

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Geosynthetics April/May 2020

Table of Contents for the Digital Edition of Geosynthetics April/May 2020