Geosynthetics July/August 2024 - 15

AVOIDING GEOTEXTILE DAMAGE
FROM OIL SPILL CLEANUP
Q: We are a riverfront landowner with a
significant 25-foot (7.6 m) riprap slope
protecting our property from erosion and
scour. There is a woven monofilament
geotextile filter under the riprap to stop the
embankment soil from piping into the river.
This system has worked well for the past 10
years, even with two 100-year storm events.
However, last month, we had a crude-oil
spill upstream from our property. Residual
oil is now coating the riprap and geotextile
of the protected embankment, and we are
concerned about slope instability. Do you
know of any way to clean up oil without
damaging the geotextile or rebuilding the
protected embankment?
A: There are two methods of cleanup
that have worked in the past. The first is a
shoreline flushing/washing with pressurized
steam cleaners and surfactants that can
rinse oil from the shoreline into the water,
where it can be more easily collected with
skimmers and trapped by booms. This is a
rather violent process that tends to sterilize
the spill area. It is tough on the flora and
fauna, and may be rough on the geotextile
filter. Please note that any remediation
procedure needs to be preapproved by
regulators prior to implementation.
The second method is oil spill remediation
via microbes. When we talk about microbes
that are able to clean up oil, we're talking
primarily about bacteria and fungi. Bacteria
can break down oil to carbon dioxide
and water. However, no single organism
can break down all the components of
crude oil or refined fuels spilled into the
environment. There are some bacteria that
can degrade several hydrocarbons or a class
of hydrocarbons. The combined action can
degrade almost all of the component crude
oil. Such microbes are readily available
through several commercial outlets. They
typically are broadcast at the spill site
with sawdust or clay carriers. Over time,
the microbes colonize to break down
the oil to carbon dioxide and water. It is
an environmentally friendly approach,
although it takes time.
LINER SYSTEM SELECTION FOR
LEAKAGE AND PERFORMANCE
Q: We recently relined an aeration pond at a
POTW with a 45 mil GRI GM-30 barrier. It was
successfully lined for 30 years with a 45 mil
CSPE (Hypalon®) liner that was, unfortunately,
punctured and torn beyond repair by a fallen
tree from outside the fence line. The relined
surface impoundment currently is leaking
greater than 10,000 gpad, even after leak
integrity surveys and three attempts to repair
it. Can you offer advice on how we can get this
facility back online?
A: You are using the wrong barrier for your
critical application. A GRI GM-30 barrier is
fine for a temporary drop in aquaculture, oil
and gas, or animal feed lot pond. However,
you are dealing with a critical structure that
needs to last for many years. Your application
is challenging and unfortunately, you chose
a barrier that is not good under tension. The
seams (extrusion and fusion) and connections
at your installation are going through
repeated thermal cycling. As such, they are
rupturing the relatively thin surface ply from
the slit film woven polyethylene scrim at the
center of the barrier and creating a multitude
of leaks within and through your liner system.
I am sorry for the bad news, but your repairs
are merely temporary bandages. You will most
likely need to tear out the new GRI GM-30 liner
and replace it with one of the following:
* GRI GM-34: EIA
* GRI GM-28: CSPE
* GRI GM-25: LLDPE-R
* GRI GM-18: fPP-R
* GRI GM-21: EPDM-R
There are hundreds of barriers and
geomembranes to choose from in our
industry for containment applications such
as yours. Unfortunately, they are not all
appropriate for critical surface impoundment
applications, particularly when the liner is
acting in isolation (i.e., performance of your
liner system will be greatly enhanced by a
GCL or CCL under the geomembrane). G
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Geosynthetics July/August 2024

Table of Contents for the Digital Edition of Geosynthetics July/August 2024
