Monitoring GSE Leak Location Liner for Leakage

TECHNICAL NOTE
A Field Demonstration: Monitoring GSE Leak
Location Liner for Leakage
The Wengfu Company is a state owned enterprise , with a large
manufacturing facility in Guizhou Province, Peoples Republic
of China. Several industrial chemicals are produced there and
the facility includes a large fertilizer (phosgypsum) processing
operation with a gypsum stack of approximately 20 hectares
and an average depth of 120 meters, a water storage pond lined
with a 1.0 mm HDPE black geomembrane that is approximately
3 hectares in size and process water ponds lined with a 1.5 mm
HDPE black geomembrane that is approximately 4 hectares
in size. Over the past decades, the area has experienced
significant groundwater and surface water contamination.
This occurred primarily during the initial operation years and
geosynthetic barriers were not utilized. Subsequently, the use
of geomembranes for containment and groundwater protection
became a standard practice and the areas environmental quality
increased significantly. Due to continued manufacturing and
existing storage capacity constraints the current gypsum stack
is expected to reach its capacity in the next few years. Plans
are underway to construct and expansion that will combine two
existing storage areas, cap a significant portion of the exposed
stack and provide a base liner layer for a significant “piggy back”
expansion. Due to the critical nature of this expansion the owner
and the provincial Department of the Environment determined
to construct a test pad designed to demonstrate the current best
available technology and to provide engineering data and training
for the inclusion of these techniques in the site expansion(s).
Testing and Results
The installation of the geomembrane was fairly straightforward. Standard quality
assurance parameters were followed including preparation of test welds, air channel
pressure testing for the dual track wedge welded seams and vacuum box testing for
extrusion welded seams. Care was taken to provide electronic isolation by leaving the
anchor trenches open and leaving the exposed perimeter edge of the geomembrane
exposed to the air. Also panel to panel connections were made with approximately
1 meter by 2 meter sections of White Leak Location Liner being placed underneath
the primary geomembrane and the two conductive surfaces connected via gravity
connections with a small hot air tack weld to assure stability of the placement. The GSE
ISO (isolation) wedge was used for all dual track wedge welds to assure proper isolation
of the conductive edges and prevent “false positive” leakage results.
GSEworld.com
GSE Leak Location Liner
Authors
B. J. Ramsey
GSE Environmental
Suzhou, PRC
N. Liu
Shanghai Jiao Tong
University
Shanghai, PRC
E. Geutebrück
Texplor GmbH
Potsdam, Germany
Field Demonstration: Monitoring GSE Leak Location Liner
Photo 1. Demonstration pad site prior to
geomembrane installation.
Photo 2. Pad after geomembrane installation.
Figure 1. GSE Leak Location Liner welding schematic with false positive result potential.
Figure 2. GSE Leak Location Liner welding schematic with ISOWedge weld attachment.
Figure 3. Spark testing.
This Information is provided for reference purposes only and is not intended as a warranty or guarantee. GSE assumes no liability in connection with the use of this Information.
Specifications subject to change without notice. GSE and other trademarks in this document are registered trademarks of GSE Environmental, LLC in the United States and certain
foreign countries.
Field Demonstration: Monitoring GSE Leak Location Liner
After completion of the installation and standard quality assurance
testing, a liner integrity survey was conducted in accordance with
ASTM 7240. The seams were particularly evaluated and several minor
installation errors were detected and repaired with extrusion beads.
At that point three monitoring modules manufactured by Texplor
were installed in a triangular geometry as pictured and illustrated on
the result schematic below. The modules are enclosed in an HDPE
(High Density Polyethylene) case and the modules were provided
with a weldable HDPE skirt/flange. The flange was traced into the
geomembrane with a slight reduction in size, the geomembrane
plaques cut out and removed and the modules placed under the
geomembrane (flange only) and extrusion welded into place. Care
was taken to avoid damage to the cables leading from the modules
to the receptor plugs. Subsequently theses welds were tested with a
vacuum box.
After installation of the modules, the wiring was connected to a
master control panel and the system was powered and calibrated.
A background state was established. After assuring the system was
fully operational, a trial hole of approximately 1.5 centimeters in
diameter was punched through the liner in a location approximately 3
meters form one of the sensors and within the triangle formed by the
three sensors. The signal of leakage/electrical disruption was evident
in less than 30 seconds. This hole was then repaired with a patch and
extrusion weld.
The site was then flooded with water to a depth of between 10-25
centimeters (depending on the location as the site sloped slightly
downhill, west to east.)
Photos 3 and 4. Module Installation.
At that point the personnel of the module manufacturer and
geomembrane manufacturer left the premises and a “blind” hole
(again approximately 1.5 centimeters in diameter was placed
in the geomembrane by the province officials present for the
demonstration. The staff returned and the lack of liner integrity was
immediately identified and data was collected to assist in calculating
the location of the “blind” hole.
Photo 5. Flooded pad with modules.
This Information is provided for reference purposes only and is not intended as a warranty or guarantee. GSE assumes no liability in connection with the use of this Information.
Specifications subject to change without notice. GSE and other trademarks in this document are registered trademarks of GSE Environmental, LLC in the United States and certain
foreign countries.
Field Demonstration: Monitoring GSE Leak Location Liner
Subsequent data analysis (taking approximately two hours)
indicated the location of the leak/hole with an estimated accuracy
within a 1 meter circle. This calculated location was compared with
the measured /actual location and varied by 68 centimeters.
At that point, phos-gypsum waste was placed on the pad to a
depth of 40 centimeters. During the waste placement, the majority
of the water was drained from the pond; however, some standing
water remained. After the waste was placed, the three sensors
were excavated and removed by being cut out of the liner system.
The cutouts were not repaired or covered with any additional
liner material. The edges of the cutout areas were lifted to assure
electrical isolation.
After that point a dipole (quadrapole) survey was done in
accordance with ASTM 7007. The dipole survey took approximately
one and one half hours to conduct and identified three potential
leaks as the outcome of a 15 minute review. These leaks were
pinpointed using the dipole apparatus and successful identified two
“blind” leaks that had been placed in the system.
Figure 3. Leak location results.
Photos 7 and 8. Cover soil placement and site
after completion.
Photo 6. Officials visit the site.
Photo 9. Diopole (quadrapole) testing.
This Information is provided for reference purposes only and is not intended as a warranty or guarantee. GSE assumes no liability in connection with the use of this Information.
Specifications subject to change without notice. GSE and other trademarks in this document are registered trademarks of GSE Environmental, LLC in the United States and certain
foreign countries.
Field Demonstration: Monitoring GSE Leak Location Liner
Figure 4. Diopole survey results.
One of the holes, nearer to the center of the site, was very accurately located to a distance of just a few centimeters.
The other leak was closer to the edge of the liner, and because of some edge distortion effects, the accuracy was not
quite as good; however, it was still within a 20 to 30 centimeter radius. The third signal could not be clearly identified as
a hole and as no excavation was done, this issue was left open.
Conclusion
The testing and data demonstrated all of the current “best practices” and “best available technologies” for barrier
systems. One of the most effective methods of assuring barrier performance has been demonstrated to be an electrical
leak location survey that is conducted after initial cover soil placement above (on) the geomembrane (Beck, 2012). The
placement of cover soil on the geomembrane has been reported to be the most dangerous time and the most likely to
result in a loss of barrier capability (Nosko). Furthermore, electrically conductive geomembranes have a very strong
history of supporting and improving the performance of liner integrity surveys (Beck, 2015). The monitoring technology
demonstrated here can provide continuous monitoring further improving environmental protection.
This Information is provided for reference purposes only and is not intended as a warranty or guarantee. GSE assumes no liability in connection with the use of this Information.
Specifications subject to change without notice. GSE and other trademarks in this document are registered trademarks of GSE Environmental, LLC in the United States and certain
foreign countries.
Field Demonstration: Monitoring GSE Leak Location Liner
REFERENCES
ASTM D5820 - 95(2011) Standard Practice for Pressurized Air Channel Evaluation of Dual Seamed Geomembrane,
American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA
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American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA.
ASTM D 7007 – 09 (2009), “Standard Practices for Electrical Methods for Locating Leaks in Geomembranes Covered
with Water or Earth Materials”, American Society for Testing and Materials, West Conshohocken, Pennsylvania, USA.
ASTM D7240. Standard Practice for Leak Location using Geomembranes with an Insulating Layer in Intimate Contact
with a Conductive Layer via Electrical Capacitance Technique (Conductive Geomembrane Spark Test), American
Society for Testing and Materials, West Conshohocken, Pennsylvania, USA.
ASTM D7703. Standard Practice for Electrical Leak Location on Exposed Geomembranes Using the Water Lance
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Landfills”, 9th International Conference on Geosynthetics, Brazil 2010, pp. 501-510.
This Information is provided for reference purposes only and is not intended as a warranty or guarantee. GSE assumes no liability in connection with the use of this Information.
Specifications subject to change without notice. GSE and other trademarks in this document are registered trademarks of GSE Environmental, LLC in the United States and certain
foreign countries.
Field Demonstration: Monitoring GSE Leak Location Liner
REFERENCES
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Weiss, B., and Geutebrueck, E. (2014). ): Next generation Leak Location in HDPE liners in landfills and other facilities
of environmental risk (Texplor MSS Monitoring System). 10. IGS Conference, Berlin, Germany.
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Landfill Symposium
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This Information is provided for reference purposes only and is not intended as a warranty or guarantee. GSE assumes no liability in connection with the use of this Information.
Specifications subject to change without notice. GSE and other trademarks in this document are registered trademarks of GSE Environmental, LLC in the United States and certain foreign
countries. 30MAR2016