LINER INTEGRITY SURVEY COURSES
On 12 March, 17 invited people from as far as
the UK, attended the first joint TRI/Environmental – I-CORP
INTERNATIONAL course on geoelectric Liner Integrity Surveys (LIS)
in Austin, Texas. A half-day classroom
session taught by Dr. Ian D.
Peggs was followed by a half day of test
surveying in three specially constructed cells with exposed, water-covered,
and soil-covered liners. The exposed liner, used for water lance surveying
was built over four different sub grades; geonet, conductive geotextile,
conductive geomembrane (conductive side up, and with a seam), and GCL
with a joint. The differences between each, and the effects of welds
and joints, were quite apparent to those performing the surveys.
Surveys were performed on artificial calibration holes then on holes
in the actual liners. A 5 mm diameter hole in the soil-covered liner
when surveyed by Peggs generated the required characteristic signal shown
below, indicating that the hole could be detected from a distance of
about 5 ft. The signal generated by the participants was not quite as
well-defined. Boundary conditions were changed such that significant
current flowed around the edge of the cell, thereby demonstrating the
significant loss of sensitivity that results.
Characteristic signal only generated by
a leak
The classroom session describing the history, theory, practice, boundary
conditions, and limitations of electrical survey techniques concluded
with an outline of new technologies for locating leaks in bottom liners
and landfill caps.
The need for such an accreditation course has
arisen with the increasing acceptance of electrical integrity surveys
as the final component of
liner CQA by engineers and regulators. Some states are requiring such
surveys. In addition, equipment packages for the different types of surveys
are now commercially available. The class, the first of its kind, presented
a unique opportunity for the attendees to learn the about the equipment
and procedures associated with this work. For those desiring formal credentials
for the performance of liner integrity surveys, the indoor and outdoor
classroom work represented the first part of an accreditation path based
on designed curriculum. The second part of accreditation consists of
field guidance and monitoring for one or two days during a student’s
first commercial survey project.
TRI and I-CORP have jointly formed the TRI-CORP Liner Integrity Center
(T-CLIC) to perform research, development, education, and training in
matters that contribute to the improved performance of geosynthetic containment
systems.
TRI-CORP would like to thank GSE, Tarkett Sommer, R.T. Clark and Leak
Sensors for the provision of liner materials and equipment.
A second course for a maximum of 20 registrants
is planned for 7
and 8 June 2004. This session will start with a 1 hr practical
demonstration in the water-covered cell, a half day in the classroom,
then a full day
with registrants performing surveys in each of the three test cells.
For further information and to register contact Melissa
Hunter (TRI) at 512 263 2101
(800 880 8378 in US), or Ian
D. Peggs (I-CORP) at 561 369
0895, or download information directly at www.GeosyntheticTesting.com.
Performing
soil-covered liner integrity surveys during TRI-CORP's electrical
liner integrity
(leak location)
survey course.
Jeff Blum of STS Consultants
performing a trial survey on the water-covered liner test cell.
 
Course attendees checking potential readings
during the survey. Seventeen registrants, from as far as the UK, attended
the TRI-CORP Liner Integrity Center's (T-CLIC) inaugural course,
organized by Sam Allen at TRI on 12 March 2004. Led by Ian D. Peggs,
a half- day of classroom sessions was followed by a half-day of test
cell surveys on three custom built cells; water-covered, soil-covered,
and exposed liner cells.
 
Photo left: Preparing the water covered liner adjacent to the soil covered
cell.
Photo right: Secondary liner covered by (from left to right) conductive
geotextile, GCL, conductive geomembrane, and geonet before primary
liner placed for exposed liner water lance survey trials.
 
Photo left: Calibration hole next to a
one-cent coin.
Photo right: Artificial calibration hole provided by exposed wire. Registrants
performed their own surveys on a calibration cell and actual 2 mm leak
in a single liner covered by water. On a soil-covered single liner
they performed surveys over an artificial calibration hole connected
into
the circuit in two different ways, and over a 0.25 in hole in the
liner with good boundary conditions and with two different types of poor
boundary conditions. An exposed double liner with four different substrates
under
the primary liner was surveyed using the water lance technique.
The
four substrates were a simple geonet, a GCL with an overlap, a conductive
geomembrane with the conductive side up (also containing a weld),
and
a conductive geotextile. This provided an excellent comparison
of the performance characteristics of the different types of lining systems.
It is expected that there will be several more such courses leading
to
accreditation of technicians for performing electrical surveys.
T-CLIC
will be developing other technologies to help assure liner integrity
and performance which will be passed on to the industry. T-CLIC would
like to thank GSE (Houston) and Tarkett Sommer (France) for providing
lining system materials, and R.T. Clark (Oklahoma) and Leak Sensors
(Connecticut) for providing additional power supplies and meters respectively.
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