With all of the technological advancements in the past several years, do we really need to perform geosynthetics CQA in the modern day?
The need for CQA was obvious in the early days of geosynthetics containment applications, as materials, installation processes, and testing processes all were in the baby stages, needing to become uniform. But what about now, in this day and age of improved materials, equipment, and advanced testing processes such as leak integrity surveys that can be done after protective cover is placed?
Granted, CQA is what many of us do for a living. So, should you and I be looking for a new line of employment in the near future? To answer that, we need to take a look into the actual role of CQA on a geosynthetics installation.
One of the greatest advancements in geosynthetics I have seen in the past twenty years is the refining of the material manufacturing process, with better controls and improvements in the chemical compositions as well as the physical manufacturing process; not to mention the development of improved materials such as conductive sheets. So, why would CQA be required for modern material deployment?
Likewise, technological advancements have greatly improved the quality of fusion welding machines, especially the dual-track wedge. Many of the modern machines can be set up by an experienced foreman, and all the welding technician needs to know is how to feed the material into the machine, and how to start and stop the machine. With a little bit of overlap cleaning and trimming, the fusion welding process seems nearly foolproof! Is there really any benefit to having CQA personnel monitoring the fusion welding? After all, a passing trial seam is usually required to qualify the welder, and the entire seam is going to be non-destructively tested. And, don’t forget, there is the destructive testing as well to confirm the seam quality!
Even the extrusion welding process used primarily for repairs has benefited from technology! The machines are lighter and easier to use with more precise control of heat settings; the welding rod itself has improved—gone are the days of the moisture and dirt trap known as hollow core welding rod. Again, the seaming is pre-qualified by passing trial seams, will be followed by non-destructive testing, and in some instances, destructive seam testing will be performed.
Significant technological advancements have also occurred in non-destructive seam testing. Does anyone remember the old air test apparatus with that needle between a set of clamps? Or those hand pumps that tended to damage the liner, sometimes even when rub sheets were used? Now we have the portable air pressure pumps and quick ways of sealing the ends of the seams. Even needle insertion seems relatively effortless with an experienced QC. Likewise, vacuum testing has monumentally improved! We used to spend what seemed like hours trying to vacuum test one patch. Those old rigid boxes have now been replaced with longer, flexible boxes that provide much better sealing capabilities, as well as visibility to see in the box.
Even the on-site destructive testing of coupons from trial seams, end coupons, or destructs has been improved by better quality tensiometers—some even pull multiple coupons at once providing increased speed of testing. With the exception of manually marking the destructive samples, it seems the whole installation process has increased in efficiency, which can be backed up by the substantial square footage now installed in a single day by a liner crew.
For comparison, in 1990, the average crew size including hired local labor was typically 8-10 people with a minimum installation goal of 100,000 square feet per day; the model of the 2010’s has an average crew size of 11-15 with minimal local labor and an installation goal of 150,000 square feet per day.
Even the model of installation crews has changed to increase efficiency—whereas hiring local labor resulted in endless training by the installer on a project-by-project basis, the installer now typically employs all crew members which provides the increased efficiency of a well-oiled machine.
Could the final nail in geosynthetic CQA’s coffin be the spark test or leak integrity surveys? Spark testing of conductive sheet offers the ability to find pinhole-sized leaks (or more obvious ones) that even the best CQA eye may miss. These are great technologies that are relatively cost-effective. And, they find leaks. If a leak is found by one of these methods, does it mean CQA was not doing their job? Do these technologies alone replace the need for CQA?
If the above summation makes you want to search the classifieds for a new career or slash the CQA budget of your next bid…don’t. CQA is not going away. Nor should it.
What happens to these awesome sheets of geomembrane if they are placed on subgrade that will damage the material itself? Are all sheets created perfect, or do blemishes and other defects exist—if so, who is going to catch them? What about stresses on the material that cause elongation and thinning, such as a rock or rut in the subgrade? Without a puncture, the leak integrity system will not catch them.
How many times have you seen someone who cannot run the tensiometer correctly, or at the wrong speed? What if there is no coupon cutter—can someone in the field quickly translate whether a hand-cut coupon 1.2 inches wide pulling a strength of 95 PPI passes a minimum 91 PPI specification? What happens to your project if a bunch of trial welds were mistakenly passed that ultimately fail in the laboratory?
How many times have you seen faulty air pressure gauges? Or even people just going through the motions, saying a test passes when you discretely observed it didn’t. Have you ever cut a destruct out of a seam labeled as passing an air test, only to find out it has no air channel—either fully sealed by the welding process, or the overlap is missing? How many times have you asked a vacuum test technician if they know what a leak is, and their response is “No, I was just told to run this machine over all the extrusion welds”? Perhaps you should ask this question and see the responses you get. Similarly, ask a vacuum test technician how long the vacuum pressure needs to be applied, and what the minimum pressure required is—the answers you get may astound you! And if you really want a mind-bender, ask the vacuum technician the overlap specification and what it means—the majority believe the overlap means the perimeter of the box, not the visible area within the box!
And, before you replace CQA with a spark test or leak integrity survey, ask yourself: what is the correlation between a sheet spark test or leak integrity survey, and the integrity of the seam? Who is making sure the spark test operator is getting 100% coverage, the liner is clean and dry enough to run the apparatus, or the operator is not jumping wrinkles or other hard to test areas?
In fact, the advancement in technology of spark testing and Leak Integrity Surveys may mean just the opposite—perhaps an increase in CQA is needed to not only assure the design is followed to allow the LIS to work, but that other long-term factors potentially negating an LIS are caught. While LIS is a great CQA tool, it is not a substitute for quality CQA. Perhaps the perfect solution for a maximized Return On Investment (ROI) in achieving an ideal liner system for the long-term involves LIS used in conjunction with good, old-fashioned, competent CQA.