IAGI White Paper
White Paper on Improving Geomembrane Installations
(download pdf 411kb)

Foreword:

IAGI sponsored a panel discussion on February 13, 2003 at Geosynthetics 2003 in Atlanta. This was part of an ongoing effort to discuss the need to refocus current geomembrane CQA/CQC procedures to reflect improved methods of geomembrane field seaming and installation being practiced today. The envisioned outcome of the discussion was to propose options for CQA procedures/methods to improve geomembrane installation quality and de-emphasize the current practice of reliance on high frequency (i.e. at 500 foot intervals) destructive seam testing that results in holes being cut in geomembranes as a traditional CQA procedure. IAGI invited panelists who are active in the field of Geosynthetics yet come from different backgrounds. These panelists led discussion on this topic from various perspectives and stirred input form the 120 attendees who attended this evening session. These discussions resulted in the preparation and adoption of the following White Paper by IAGI.

With little exception, construction quality assurance procedures have remained unchanged for over a decade. The end result is that in order to document installation integrity, it is standard practice to cut holes in perfectly good geomembrane. And as is currently the case for polyethylene geomembranes, where the predominant seaming technique is double wedge welding, after cutting out a section of good seam just to show ourselves that the seam is good, the industry proceeds to patch it with an inferior seaming technique that often goes unchallenged with respect to the latter’s integrity.

IAGI is of the opinion that the geosynthetics industry should have learned a thing or two about the installation of geosynthetics over the course of the last 20 years and that as a result of this learned experience, the industry should have a better approach to verifying that a liner will not leak than systematically cutting a holes throughout it.

Information provided by Mark Cadwallader represented that global destructive seam failure rates have declined during the period from when they were first monitored until today. When initially reviewed, destructive seam failure rates were on the order of 7 percent. It has been presented that today’s data suggests a failure rate of less than 2 percent. This reduction in observed failure rates is attributed in great part to the increase in both the application and proficiency of construction quality assurance, an increase in the level of experience of the geosynthetics industry and specifically geosynthetics installers, and the industry’s shift to automatic dual track hot wedge seaming equipment.

Although part of this reduction in failure rates has been attributed to improvements in CQA, no credit has been given in the CQA program acknowledging other advancements in the industry. Advancements have been made in seaming equipment as well as in integrity monitoring systems. A review of some of the advancements in both construction and CQA has lead to the suggestion of the following in terms of suggested reduction in destructive seam testing associated with application of these techniques:

We are now able to perform 100 percent geomembrane integrity monitoring utilizing electrical leak location methods – a technique that has proven itself to be orders of magnitude more sensitive than destructive seam testing or vacuum box testing. But more than this, electrical methods allow us to take that quantum leap from only testing seams to now being able to gauge the overall integrity of the entire system in real time.

With an eye to performance of integrity monitoring for the complete installation, a relaxation to the number of controlled discontinuities introduced into a lining system through destructive testing appears to be the next logical move for the comprehensive CQA program. This white paper therefore looks at the basis and methods for making measured approaches to the reduction in destructive seam testing.

(download pdf 411kb)