Geosynthetics April/May 2024 - 13

TEMPORARY INTERIM COVERS
Q: I am writing to inquire if you are aware
of any recommendations or guidelines for
removal of geosynthetic liners that have been
used as temporary interim covers at landfills.
We recommend facilities totally take up and
remove the temporary cover; however, we
have had some recent proposals to run over
the liner with heavy equipment with the
assumption that it will tear holes and damage
the liner sufficiently. I still have concerns that
the damage will not be adequate to prevent
ponding or seeps and could cause potential
instability in the waste if landfill operations
are resumed in these areas. If you have any
thoughts or are aware of any research or
guidance on this topic, please let me know.
A: We would strongly recommend totally
taking up (i.e., removing) all the material
from the temporary interim cover before
construction of the final cover. This is
supported by evidence from at least five
case histories. In all five cases, the old interim
cover created a partial barrier in localized
spots and created a mess with mildew and
trapped moisture. In addition to this partial
barrier concern, the old interim barrier in
three cases served as a weak shear interface
with adjacent materials. This created both
global and localized shear failure on a
relatively shallow slope (less than 4:1).
In addition, please consider recycling
your temporary interim covers from the
perspective of both benefit cost and
sustainability. There are several companies
specializing in this service. They recycle
huge amounts of geomembrane liner from
both depreciated landfill covers and surface
impoundment. They can even handle
geomembranes that are scrim reinforced.
The process is entirely closed-loop, and
accepts geomembranes after screening
for contaminants. The " scrapers " clean and
shred the material on-site, and then it is
incorporated into commodity plastic used
for non-critical applications or sold to the
open market. I am awed by the diversity and
scale of the market for used, reground and/
or obsolete plastics. It is not only good for the
environment but good business. Please note
that like all materials, traceability is important
and the durability of recycled plastics might
be suspect.
GEOMEMBRANE TESTING
Q: We are a geomembrane manufacturer
and have a client who asked us to test an old
geomembrane that we sold to them 20 years
ago for a surface impoundment. They are also
asking us to test a competitor's geomembrane
used at the same site. Can we issue a formal
report to a governing agency of results on
such geomembranes-one that we produced
and one from a competitor?
A: For starters, this is a complex question that
is better asked of an attorney rather than an
engineer. However, I can tell you that most
good manufacturers have a keen interest in
field performance of their materials and are
always testing aged-exhumed materials FOR
INTERNAL USE ONLY! If you are going to do
this and share the results within an informal
report with your client, I would strongly
suggest that you include the following three
clauses in your report:
1. It should be noted that the test specimen
and test sample used for this report was
believed to be representative of the
material produced under this designation.
However, these results are indicative of only
the specimens that were actually tested.
2. The testing herein is based upon
accepted industry practice as well as the
test method listed. We neither accept
responsibility for nor make claims to the
final use and purpose of the material
beyond the original warranty.
3. It is specifically requested that this
document be considered proprietary
information and should not be
reproduced, except in full, without the
written approval of " our company. "
All of that written, your company
cannot submit a formal report on such
case histories to a government agency
and especially not on a competitor
geomembrane. This is a conflict of interest
and strictly forbidden. To be viable,
such reports need to be submitted by
a consultant working for a third-party
laboratory or a research institution with
peer review. G
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or email your technical questions
to gmatechline@textiles.org.
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Geosynthetics April/May 2024

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