Waste management regulations, landfill construction techniques, and approaches to daily operations and final cell closure vary wildly around the world; but the waste management industry on the whole is in better shape than most, if not all, common areas of infrastructure.
This has a great deal to do with the roles that geosynthetics and their affiliated quality control measures play in modern cell construction and monitoring.
This year I’ve had the opportunity to discuss electrical leak location (liner integrity) construction quality assurance (CQA) with two renowned experts in the field: Mr. Robert Phaneuf (New York State) and Dr. Werner Müller (Germany).
While these conversations only scratch the surface, they reveal a fascinating way in which the United States and Germany provide disparate but equally valuable approaches here. Both have thorough regulatory systems for all phases of waste management, but in regards to liner integrity survey systems, one focuses primarily on the bottom liner quality check and the other on the cap.
THE VIEW FROM NEW YORK
“The New York State Department of Environmental Conservation (NYSDEC) is developing new landfill liner standards that will require electrical integrity surveys on both primary and secondary geomembrane liners at the State’s municipal solid waste landfills,” reports Robert Phaneuf.
Phaneuf serves as the Acting Director of the Bureau of Hazardous Waste & Radiation Management, Division of Solid & Hazardous Materials. His bureau is part of the nationally influential NYSDEC.
Rules and regulations adopted in New York are often adopted by other states. New York, with its large urban population and concern for the preservation and protection of the state’s water quality, is usually by necessity at the forefront of regulation.
“Surveys are already routinely being performed on primary geomembrane liners at most of New York State’s double-lined municipal solid waste landfills,” Phaneuf says.
What’s interesting here is how the state has used voluntary programs in order to collect the appropriate evidence and hold the right discussions before moving forth with more liner CQA regulation.
Based on information gained from the voluntary performance of liner integrity surveys on primary liner systems, a marked improvement is noted in way of fewer construction related defects being found when the liner integrity survey is an integral part of the construction specifications. Seeing this benefit, and when one considers the importance of construction quality on the overall performance of the liner system coupled with the long-term uncertainties associated with liner systems needing to function for an undefined period of time, a requirement for surveys for both lower and upper liner systems makes sense.
“It’s all about construction quality and acceptable long-term operational performance,” says Phaneuf.
Leak location testing then serves to verify that the approved barrier materials have been installed properly as the last step before allowing waste to be placed into the cell.
Phaneuf also notes that the state’s proposed regulations do not impose liner intergrity surveys on final cover systems because final covers are easily accessible in the event of a problem being detected.
The approach in New York is that landfill final cover system construction follows the state’s standard CQA protocols and construction certification requirements. In the case of suspected cover system defects after the site is closed, an electrical integrity survey can be conducted on a as-needed basis during the post-closure care period of the landfill.
THE VIEW FROM GERMANY
In Germany, liner integrity testing is used for CQA on landfill caps—not on bottom liner systems.
“The approach at the base of the landfill is to use a composite liner: a clay liner and an HDPE geomembrane,” says Dr. Werner Müller, head of the Working Group on Plastics in Geotechnical and Geoenvironmental Engineering for Germany’s Federal Institute for Materials Research and Testing (Bundesanstalt für Materialforschung und –prüfung, or BAM).
The idea is that when these composite systems are installed, there is enough redundancy for assurance. Small leaks in a geomembrane are not necessarily relevant because of the clay liner beneath it.
German regulation focuses more on permanent monitoring methods.
“The problem is that if you have a permanent leak detection system at the base,” Müller says, “the question is always what would you do if you found some leakage?”
This does not suggest a lack of concern in Germany for the bottom liner systems. Regulations are stringent on material quality, selection and installation not only for geomembranes but also on compacted clay liners. Thick, certified geomembranes must be used. Smart welding must be used. The presence of quality materials, experience and proven practices, thus, produces a safe site.
“Originally, we were set to make the same rule on the cap as at the base—a composite liner system,” says Müller. “But then people found a lot of problems with compacted clay liners in a capping system.”
Major problems included desiccation and root penetration.
The discussion then went away from compacted clay and into other capping system combinations.
“For example, there are bentonite mats and polymer-amended sand/bentonite mixtures to combine with a geomembrane,” says Müller. “But the other idea was to use a leak detection system in combination with a geomembrane. In capping, leak detection can now be used as an alternative to other liner components.”
Leak detection becomes the check in the cover that clay serves in the base.
This long-term monitoring of landfill cap quality requires approval. To date, only two companies have qualified to perform the cap integrity monitoring: Progeo GmbH and Sensor Dichtungs-Kontroll-Systeme GmbH.
Approval of capping systems and capping system integrity monitoring requires many things, such as the ability to properly perform and understand material selection and testing: long-term behavior of the geomembrane, stress-crack resistance if using polyethylene, resistance against oxidative degradation of the leak detection system cables, and so on.
To get certification to perform these services for a site requires passing a model installation in which the system and the accuracy of the integrity monitoring are vetted by third-party controls.
“There are requirements for lightning protection and documentation and quality control and so on,” says Müller. “If in one case the system was properly installed and it’s been shown that there’s enough resolution and the material properties of the cables and sensors and electrodes are okay, then they can get certification.”
Beyond that, when used on a landfill site, there must always be testing even though an approved system is being used. Artificial holes, for example, are placed in the liner system by a third-party controller.
Chris Kelsey is an editorial consultant to geosynthetica.net. He welcomes your insight towards future articles on landfill liner integrity and all other subjects involving geosynthetics. He can be reached at chris@geosynthetica.net.
