Geosynthetics February/March 2022 - 9

EPDM LINER FOR A
WATER APPLICATION
ELECTRICAL LEAK
DETECTION AT DEPTH
Q: We are looking at a life-cycle study for the
usefulness of an ethylene propylene diene
monomer (EPDM) based geosynthetic liner
for a water conservation application. Request
to kindly share the information for our study.
Regards.
A: EPDM is going to lie flat on the subgrade
soil without wrinkles (no field-induced stress).
Therefore, it will have intimate contact with
the soil above and below it. This results in
a composite action for the barrier layers if
the adjacent soils are fine grained (clay).
EPDM also will not have issues with thermal
coefficients of expansion and contraction.
Hence, it will stay put once you place it.
Unfortunately, the durability and aging
characteristics of EPDM is less than highdensity
polyethylene (HDPE) for most
environmental conditions. Like most things
in life, there are trade-offs.
Q: I am taking the opportunity to ask a
question about the electrical leak detection
(ELD) test for geomembranes:
We have the area covered with silt from the
past rainy season, and it is estimated to be
about 5 feet (1.5 m) deep worst-case scenario.
The liners in this area were not properly
inspected and signed off on by me due to the
COVID-19 pandemic and resultant lockdown.
The water is in the process of being pumped,
and the pond will soon be empty.
My question is, will ELD be able to detect
leakages at this depth at all? I have no
experience with ELD yet. Removing the silt is
an option, but the client doesn't want to go
this way, and it could cause more damage to
adjacent liners.
Can the area be covered with a sacrificial liner
over a 60-mil (1.5-mm) wedge-welded liner
to the existing 60-mil (1.5-mm) liner? Will
unwanted stresses occur once loaded
and will later failures possibly occur?
Thank you for your time, sir. It is
really appreciated.
A: Don't pump the water out of the cell yet.
Run the dipole method, per ASTM D7007
" Standard Practices for Electrical Methods for
Locating Leaks in Geomembranes Covered
with Water or Earthen Materials, " with some
water covering the silt. It will greatly heighten
the sensitivity of the survey. This ELD will be
able to detect leakages at depth. I have seen
this technique pick up pinhole-size leaks
through both soil and water. You are going to
need a very good survey crew to locate the
damages post-survey and dig it up; however,
it is done regularly here in the U.S.
This idea of covering the area with a sacrificial
liner over 60-mil (1.5-mm) wedge-welded liner
to the existing 60-mil (1.5-mm) liner sounds
bad to me. At that point, it is time to rip it out
and start over. Band-Aids usually do not work
for the long term.
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Geosynthetics February/March 2022

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