Geosynthetics April/May 2023 - 24

Contamination from a leaking geomembrane-A necessary and imminent evil?
resistance, thermal stability characteristics,
chemical resistance, UV resistance,
seam strength, permeability, coefficient
of friction and many other properties
may need to be taken into consideration.
This article explores how this task can be
simplified by removing one of the most
important and potentially less predictable
variables: corrosion.
John Scheirs' 2020 webinar and
Many geomembrane
materials contain additives
that help provide or
enhance needed properties
like UV protection and crack
resistance. While the base
material may be suitable for
the foreseen conditions,
these antioxidants/
plasticizers/stabilizers can
be subject to chemical
attack or degradation.
document on the " Periodic Table of
Geomembranes " illustrates the wide
range of available materials to select
from. Each has its advantages and disadvantages,
but each also has some susceptibility
to corrosion-except one category.
Inert liners eliminate the
corrosion variable
Different geomembrane materials can
be selected to guard against corrosion,
depending on the expected chemical
exposure. During the early design phase,
it is critical to know what chemicals the
liner will be expected to be exposed to
and therefore to resist. A material selection
can then be made, and clear instructions/directives
for its use can be established
and provided to the user. During
the entire life of the liner, it is then critical
to ensure that only the chemicals the liner
was designed to contain are what the liner
ends up being exposed to. While every
attempt can be made to predict what
will be put into a landfill or containment
area, there is always a risk that something
unforeseen may be introduced.
There are situations when exposure
to certain amounts of a particular chemical
is expected. One such challenging
industrial process, the Bayer Process for
manufacturing alumina (and ultimately
aluminum metal), results in bauxite residue
with an average pH of 11 (pH range
of 9-13). With such severe alkaline exposure,
an inert liner is a necessity to avoid
long-term contamination. Clearly, this is
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Geosynthetics | April May 2023
an industrial case where a typical highdensity
polyethylene (HDPE) liner will
not be a long-term barrier to leakage due
to corrosion.
There are also unexpected results that
can lead to entirely unpredicted concentrations
of chemicals. Most, if not
all, geomembrane applications are susceptible
to combinations of chemistry,
temperature and/or moisture. Chemistry
can change over time as the contained
materials decompose and mix with each
other. As the biodegradation takes place,
heat may result, thus hastening the degradation
of a geomembrane. As moisture
gets introduced, new chemicals may
result from the new molecules that have
formed as the result of biodegradation.
Geomembrane materials with an inability
to handle the full pH range of 0-14 are
ill-equipped to survive a witch's brew
scenario in a challenging landfill with
many variables.
There are many items considered
household hazardous waste (HHW)
that are not permitted in landfills.
These include paints, solvents, bleach,
batteries, household cleaners, glue and
adhesives, electronics, oil mixtures, etc.
Many of the HHW items are extreme
pH products that are incompatible with
geomembrane materials. Given the
extensive list of HHW products used in
the typical household, it is not hard to
conceive that even households with the
best intentions put extreme pH products
into their garbage.
Should the world rely upon perfect
behavior of household and business disposal
practices or is it safer to assume
bad behavior and noncompliance? From
a long-term safety perspective, assuming
good behavior over bad behavior
results in failure. Systems must be
designed around bad behavior to provide
an indefinite safety sustainability. The
same is true for geomembrane systems.
The geomembrane material should be
Geosynthetics April/May 2023

Table of Contents for the Digital Edition of Geosynthetics April/May 2023
