Geosynthetics October/November 2022 - 19

Evaluating new technologies
to limit geomembrane
destructive testing
By Evan Andrews, P.E., PMP and Kenneth R. Daly, P.E.
F
or almost 40 years, the generally accepted destructive test rate for geomembrane
seaming has been one sample for every 500 feet (152 m) of seam.
On large projects this leads to hundreds of holes cut into liners that engineers,
manufacturers and installers work very hard to make leak proof. With a typical
failure rate for most installers in the 1%-2% range, why do we continue to cut
and patch perfectly good seams? With modern materials and equipment, is there
a way to limit destructive seam testing?
Geomembrane seaming destructive sample origins
In 1987, Thomas Wright authored the Manual of Procedures and Criteria for
Inspecting the Installation of Flexible Membrane Liners in Hazardous Waste Facilities
(Wright et al.) under contract with the Hazardous Waste Engineering Research
Laboratory of the U.S. Environmental Protection Agency (EPA). This appears to
be the origin of the one-seam sample in 500 feet (152 m) frequency. Subsequent
articles on the topic refer to this work as the industry standard for installation
practices and testing. Interestingly, the actual recommendation in the text refers
to a minimum of one test per seaming crew per day and only taking destructive
samples when there is an insufficient number of construction quality assurance
(CQA) inspectors to observe each seaming crew fulltime or when the results of
testing nondestructive samples indicate poor seam quality. A review of literature
at the time points to using judgment and performance of the installation crew to
base sampling frequency on a project-by-project basis. Wright's work in 1987 only
states that one test every 500 feet (152 m) of seam is " normally required " (Wright
et al.) and is not an absolute.
Considering current-day practices, the industry, its products and its installation
methods have matured. However, the concept of using judgment and
adjusting seam sampling based on performance has been widely replaced by
prescribed values.
A geomembrane installation cannot be completed without some number of
repairs due to welder burnouts, " tee " seams or nondestructive test failures among
other normal installation conditions. However, randomly cutting destructive
seam samples based on a seaming distance may add unnecessary geomembrane
PROJECT HIGHLIGHTS
GEOMEMBRANE
DESTRUCTIVE TESTING
CONTRACTOR
Sequoia Services
ENGINEER
Wood Environment & Infrastructure
INSTALLERS
Chesapeake Containment Systems
(CCS); Environmental Specialities
International (ESI)
PRODUCTS
AGRU HDPE Geomembrane with
Clean Seam technology; Leister
Geostar Welder; Demtech VM 20/A
with Pro Data
ACKNOWLEDGEMENTS
NC Department of Environmental
Quality (NC DEQ); International
Association of Geosynthetics
Installers (IAGI)
Evan Andrews is the chief engineer for Sequoia
Services, a heavy civil contractor located in
Greensboro, N.C. He was formerly a lead
engineer for Duke Energy in its landfill programs
group and a regional manager for solid waste
consultant Joyce Engineering. He is a professional
engineer in six states and serves as a liaison to
the International Geosynthetics Society, North
American Chapter from the CCR industry.
Ken Daly is a principal civil engineer serving as
Wood Environment and Infrastructure's solid
waste/CCR practice lead based in Charlotte, N.C.
He has over 26 years of experience in engineering
design, permitting and construction of solid waste
management facilities. Since 2007 he has served
as the lead engineer, project manager and its
program manager for numerous CCR landfill and
impoundment closure projects.
All figures courtesy of the authors.
GeosyntheticsMagazine.com
19
http://www.GeosyntheticsMagazine.com
Geosynthetics October/November 2022

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