Every Weld Holds the Line:
Why Destructive Testing of Extrusion Welds Can’t Be Optional
By Richie Deason, CEO, Atlantic Coast Consulting, Inc.
The Seams that Matter Most
Landfill liner systems are the frontline defense against environmental contamination. Designed with precision, engineered for longevity, and backed by millions in materials and oversight, these systems are built to protect. But their success often hinges on a single, deceptively small detail: the weld.
And not just any weld—the extrusion weld.
The Overlooked Risk Hiding in Plain Sight
In geomembrane liner construction, fusion welding is the workhorse. It handles the long, continuous seams that make up the majority of an installation. Because it’s automated and relatively consistent, it gets most of the attention during quality assurance. And since it represents the lion’s share of the work, it also gets the lion’s share of the testing.
But here’s the irony: most weld failures don’t happen in those long seams.
Extrusion welds—used for detail work, patches, penetrations, and repairs—make up a much smaller portion of the system. But they carry a disproportionately high level of risk.
At ACC, we’ve tracked destructive testing results over the past 15 years, drawing from field-based, random sample data—not just trial seams. What we’ve found is eye-opening:
That’s more than four times the failure rate. In practical terms: for every 100 extrusion welds, nearly 10 may be compromised—compared to just 2 out of 100 fusion seams.
We acknowledge that this data is based on our own experience and therefore limited. But it’s some of the only longitudinal data available from actual random field sampling of extrusion welds. Unfortunately, many QA programs allow trial seams—done under ideal conditions—to count toward destructive testing requirements. That means the industry has very little real-world data on how extrusion welds actually perform once they’re in the ground.
We’d love to see more data. But until the industry prioritizes field testing of extrusion welds the way it does fusion seams; we’re operating with blind spots in the most failure-prone areas.
And that’s not just a technical gap—it’s a missed opportunity to catch problems early and protect the integrity of the entire system.
Extrusion weld failure rate: 9.75%
Fusion weld failure rate: 2.1%
And what does failure actually mean?
When a weld fails in a landfill liner system, it compromises the one thing designed to contain contaminants. Even a small flaw—like a poorly welded patch—can open a pathway for leachate to escape the waste mass and begin seeping into surrounding soil or groundwater. Sooner or later, that breach will show up in the groundwater monitoring data. And by then, you’re not just dealing with a failed seam—you’re looking at potential environmental contamination, regulatory violations, and a remediation effort that could take years to fully resolve.
The cost? It can be enormous.
The irony? It’s preventable.
For less than $100 destructive test on that extrusion weld—plus the cost of installing one more patch—could have confirmed the seam was sound from the start. Instead of a slow-moving crisis, you get peace of mind. That’s the value of testing. That’s the case for treating extrusion welds with the same scrutiny as every other part of the liner system.
Why Extrusion Welds Deserve More Scrutiny
Extrusion welding is a manual, multi-step process involving surface grinding, cleaning, heating (lystering), and the actual extrusion of plastic into the seam. It often requires multiple technicians working in tight spaces, under variable site conditions. There’s no automation to smooth out inconsistencies. Every weld depends on the skill, timing, and coordination of people in the field.
Which means: every extrusion weld is an opportunity for error.
And yet, because they’re used in smaller areas or for repairs, extrusion welds often get treated like second-class seams—easily overlooked, under-tested, and underappreciated.
At ACC, we believe the opposite: these are the welds that deserve the most attention.
Not All Testing is Created Equal
One of the biggest misconceptions in liner Quality Assurance (QA) is that non-destructive testing (NDT) provides equal confidence across all weld types. In reality, fusion welds benefit from far more precise and dependable NDT than extrusion welds do.
Fusion Welds:
These are tested using the air channel method, where the seam includes a built-in channel that’s pressurized to 30 psi and held for 5 minutes. Pressure loss can be monitored in real time with gauges, providing an objective, quantifiable, and highly accurate measure of seam integrity.
Extrusion Welds:
Here, NDT is done with a vacuum box test—usually a site-built device with soapy solution applied over the weld. The technician pulls a vacuum and watches for bubbles through a sheet of Plexiglas.
While conceptually simple, this method introduces a host of variables:
Is the vacuum box sealing properly?
Is the Plexiglas scratched or fogged?
Can the technician distinguish actual leak bubbles from the soapy solution itself?
In short, extrusion weld NDT relies heavily on human judgment and environmental conditions—making it far less reliable than its fusion counterpart.
Which is why destructive testing isn’t just recommended—it’s essential for extrusion welds. It’s the only way to be sure.
Our Approach: Test What Matters
At ACC, we apply the same destructive testing frequency to extrusion welds as we do to fusion welds—typically one test per every 500 linear feet of welding. While many QA programs test fusion seams thoroughly and treat extrusion welds as an afterthought, we treat them with the seriousness they deserve.
Extrusion welds are more failure-prone and harder to assess non-destructively, so they require equal—if not more—oversight. We track them, log them, and test them. It’s not about going above and beyond—it’s about doing what’s right based on the data and the risk.
The Bottom Line: Why Take the Risk?
Let’s be real.
We’re investing serious money into these liner systems—for good reason. They’re critical infrastructure designed to protect the environment for decades. But the weakest link in the whole system? It’s the extrusion welds.
They fail more often. They’re harder to test non-destructively. And they’re often overlooked.
Yet the cost to perform destructive testing is minimal. The impact on the construction schedule? Barely noticeable. We’re not talking about a major delay or expense—we’re talking about a basic quality check that ensures the system works as intended.
So why wouldn’t we do it?
If we’re building a system to protect the environment, then let’s test the whole system. Let’s stop assuming—and start verifying.
Because when it comes to environmental protection, “good enough” doesn’t cut it. Every weld matters. Every seam counts.
And we owe it to the environment—and to the people trusting us with it—to make sure every liner performs exactly as it was designed.
Every weld is a promise.
A promise to protect the groundwater. To uphold compliance. To stand between what’s contained and what could be compromised.
At ACC, we stand by that promise. That’s why we treat extrusion welds with the same seriousness as any other part of the system—and why we commit to thorough, field-based testing on every project we touch.
If you’re leading a landfill operation and want to ensure every seam lives up to its potential, let’s talk. Reach out to ACC—we’re here to help protect your investment, your permit, and most importantly, the environment.